Unless you can a find a set of 2” headers that have already been fabbed up, this will be a custom build.  You might ask Jerry Christenson if he can help out in this regard.  His contact information is located in the Links section.

    That means you'd need to take the car to them and leave it for a hile while they/ or Jerry build a set. Not gonna be cheap. 

I found Jerry's website last night and the standard 1-5/8 headers he makes look good.  I have a call into him so can discuss things.  2-inch may be over the top for flow through the 312 heads, even when ported out.  That is the type of info I don't know and am looking for some advice.  If 1-5/8 pipes are adequate on similar engines, why go bigger?  The Red's headers site doesn't give enough information to tell exactly what they provide, but with your answer and Frank's below, I can call and find out some more.

Thanks for the help.

I will check this out.  See my comments to Ted above.  Thanks for the help.

For a normally aspirated and ‘full race’ Y, I find that 1¾” header tubes work well.  In this instance, increased displacement, camming, compression ratio, head work, etc. all add to the need for larger sized header tubes.  The tube lengths as well as collector sizing/lengths will be dependant on the specific combination.  As a general rule, being too big on header tube size is not as detrimental as being too small.  But if capping off the headers with any kind of restrictive exhaust system, then the benefits of a header that is optimally sized for open and full throttle operation essentially becomes a moot point and a smaller sized header tube in this instance will be just as or more effective.

But blown engines break all the rules where they tend to prefer larger tubes than what is optimum for a normally aspirated combination.  Randy and I decided on 2” tubes with a 3½” collector on his blown engine combination and that seems to work well.  8.15 seconds @ 163mph and still more left in the engine but the chassis is at its limit.  But no header testing was done to quantify exactly what the engine really wanted and based on the ear ringing crackle, larger wouldn’t have hurt and indeed may have been of additional benefit.  Knowing that a blown application typically likes a larger sized header tube, we just took a stab in the dark on the 2” size and that ended up working just fine but this is a full race application with 15 lbs of boost and no street driving being considered.

And do talk to Jerry about this as he does have some experience with blown Y applications and may have some specific thoughts on the subject.  If you’re planning on running a full exhaust system, then make sure the system is as unrestrictive as possible. 

And for anyone else having trouble finding Jerry’s contact info, here's the link:

Thanks for the very interesting observtions about header pipe diameter.

I am building a 292 truck block to 331 cid with 292-diameter mains, offset ground crank, 3.880" bore, and 6.2-inch H-beam rods for a 351W stroker.

I am using 471 heads that are ported to the max and equipped with large exhaust (and intake) valves.  The intake valve lift will be .472" and exhaust lift of 0.480" with 1.6 rockers.  I will run two 500 cfm AFB carbs with the blower and a modified intake manifold.

I plan to run between 6 and 12 pounds boost , gearing the blower for a 6200-rpm redline, on the theory I probably can't cram any more air through the heads than what this will produce for a car I can readily drive on the street.   In other words, I expect the air flow through the heads to max out, i.e., the valve sizes and lifts will probably equal or exceed the flow capacity of the ported heads.

I have seen this setup on a similar engine that read about 3 to 4 pounds residual boost at the intake side with wide open throttle, so expect I would gain very little with higher boost.  The latter numbers tell me more boost will simply increase the boost on the intake side with very little increase in flow through the engine.

How does the above idea compare with your experience?

Based on the above concepts, I recognized I needed to eliminate any resistance in the exhaust and picked 2-inch header pipe as a "reasonable" sounding size, knowing it had to be quite a bit bigger than stock.  I also recognize the diameter of the header extension may have quite a bit of effect on torque.  Based on the above concepts, does 2-inch diameter pipe sound large enough?

I am not confident I can fit anything larger into the car and still retain its stock appearance.  I am not without resources to bend some of my own pipe if need be, and plan to put on either multiple exhaust pipes or large (3-inch) dual pipes behind the headers to reduce any restriction at that end of the system.  If worst comes to worst, I can also try to fabricate my own headers, but time to do things is my great limitation, so would like to buy something that I can bolt on to save time.

I will definitely talk this over with Jerry Christisen and get his insight, but am curious to hear your comments about sizing the header pipe diameter for the above setup.  I doubt it will flow near as much as your full race setup.  At the end of the day, it sounds like I am definitely better off with 2-inch pipe than with 1-5/8, even if it is still smaller than the optimum.  If I were willing to cut holes in the fenders, size would not be an issue.

I did not notice your message on page 2 before responding to Ted's message.  I am getting a lot of good ideas here and obviously have to continue working on this.  Sounds like my main limitation may be trying to squeeze larger diameter header pipes into a car without routing through the fenders, which I will not do on this particular car.

I did not understand your comment that you got your headers from Jerry just in time.  I have tried to reach him without success the past week.  I hope he is OK.

No apology needed.  I just wanted to make sure I understood.  Regarding your detonation problems, I melted the corners off a good set of pistons and broke all the rings in a small block 400 in my 78 Ford pickup a few years ago.  I thought part of the problem was my old ears not hearing the detonation, but have been told since that with the new gas these days, you can't hear it pinging.  I put in pistons with less compression, and not trying to optimize performance in that rig, I welded a small knob on the spark advance lever to prevent it from advancing too far.

The 312 I am building for a blower will run relatively low compression, thus eliminating a lot of tendency to knock.  That and a good modern electronic ignition system should keep me out of trouble.  Has anyone tried an antiknock sensor on a Y-block?  I wonder if they will work with solid lifters thumping away?

That’s a lot of boost.  Suggest you retap the block and redrill the heads for ½” head bolts for an increase in head bolt torque.

Exhaust flow is important in your case so concentrate heavily on the exhaust ports.  I had the same intake flow limitations with Randy’s 113 heads that you have but boost breaks all the rules in that it will force the flow in place rather than just have it flow in a more docile nature as in a naturally aspirated engine.  Even if you have more residual boost before the open valve, you will still benefit from the increase.

If you can make the 2” headers work in your chassis, then go for it as the major bottleneck in your system will be at the head just after the exhaust valve.  The gases can then freely expand into the 2” pipes and provide a bit of scavenging that you wouldn’t have otherwise at full throttle.

The 2” theory only works at full throttle and then only if the exhaust system itself is relatively unrestricted.  The same thought process should also apply to Turbos.

       For what it's worth the diameter of the primaries would be based on the horsepower you plan to make. It's basically a function of the volume of exhaust gas you generate and how fast you want it to travel. For a number I'd go to about 1 3/4" primary, as long as you can get them in the car, and a 3" collector. I think that's about where Hoosier is with his fenderwell headers, and it works for him. The 2" will kill any low end you'll have left, for street use.

       Are you talking to Frank Stubbs?   

       Stubbs is well known in the Y Block community. He produced a series of "F" code air cleaners and is considered quite an expert on all things "F" code. I have one of his reproduction air cleaners on my F code Custom 300.

For my application, which will use up to 10 or 12 psi at the blower outlet at 6000 rpm, I can expect to get about 6 psi in the intake manifold because I am using high output impellers and high flow components all through the ducts, bonnet, carbs, and heads.

Given the above, the concensus is that the 2-inch primary header pipes I considered would increase high-end horsepower, but at the sacrifice of low and mid-end performance.

Because I am building a car for the street, Jerry Christenson and Gord McMillan both recommend that 1-5/8 headers and 2-1/2 inch extensions (collectors) 2-1/2 inch exhaust pipes will give the best low and mid-end performance for street use with a small sacrifice of high-end horsepower.  This is also consistent with the comment from Frank/Rebop.

If I were building to race, I would follow Ted Eaton's advice that bigger is better and go with at least a 2-inch or 2.5 inch primary and bigger extensions.  Note that Ted cautioned me that his experince was for high end performance for racing, not a street machine.

In the final analysis, I think I will experiment with tri-Y headers, probably from Stan's Headers in WA, to get some scavenging effects while feeding into a 2-1/2 inch collector.  I am in Montana, so WA is not too far to take the car, if Stan's needs to custom fit things.  Anybody out there running tri-Y's on a Y-block?  How do they work?

    In a somewhat direct comparision, Hoosier Hurricanes engine is similar to mine except more cam, and ported heads. Mine are very close to stock, as is the cam. the major difference is John's fenderwell headers versus cast iron manifolds. He is at least 100 hp stronger than I am. The Hurricane has gone 119 mph, I've gone 106. You can check with Hoosier, but I believe his headers are 1 3/4 and 32" primaries.

John in Selma, IN

Don't feel bad!  I didn't know the dimensions until yesterday when I went out and measured them.  I had just bought them and blindly bolted them on.

John

Also, they can be purchased with a metallic-ceramic finish.  Does anyone know if the metallic-ceramic finishes stand up to the exhaust temperatures provided with a blower?

The Pacesetter header add is at www.car-stuff.com/store/?N=10359+4294963821+1616+11920+9125

Turbocharger and supercharger boost is the same.  A turbo system is a little more dynamic.  Since it's not belt driven, the boost pressure is not a function of engine rpm.

My earlier comments about boost were made to provide some idea about how much air I need to run through the engine as one factor to consider in selecting headers.

I may have mentioned somewhere above that if you measure boost from the supercharger I plan to use, at about 6200 rpm it will show 11 to 12 psi at the blower outlet.  If you measure the same pressure in the intake manifold, after various losses through the carbs, etc., you will see no more than 6 psi, maybe less.  That is because of friction loss in the system.  Typically, boost has traditionally been measured at the blower outlet, but measuring manifold pressure is a better indicator of what may be reaching the valves, where even more friction loss occurs as air flows through the head to the cylinder.  I am not sure where you are measuring the tubo boost on the Powerstroke, but it is likely somewhere near where the air enters the head, thus 15 psi of boost on your diesel is probably equivalent to the 6-psi I would read in a Y-block manifold when the supercharger is putting out 11-12 psi at its outlet.  If so, the diesel turbo is adding a lot more boost than I plan to add to a gas Y-block for street driving.

Getting back to the header issue, everyone seems to agree that going to more than 1-5/8 inch primary pipes on the header will cost low and mid-range power on a street car, even with the supercharger.  I accept this, but I am not sure I understand exactly why this happens.  Can anyone explain this?

    The diameter size thing is an issue of exhaust gas speed, or velocity. The idea is that there is a range of speeds that will help extract spent gasses from the chamber, with out going so fast as to create more friction than the inertia of the gas can overcome. It's strictly an issue of the volume of gas versus the area of the pipe. More displacement requires a larger pipe, and more RPM from the same displacement also requires bigger primaries. The length of the pipe controls the the time or RPM that the wave returning from the end of the pipe, reaches the exhaust valve. Longer pipes require more time for the wave to travel back and forth, and therefore work better at lower RPM's.

   There's a number of Formulii for this but most of us use the empirical results from other guys pipes. (we watch to see what works) and then, of course you have the issue of fitting the headers into the car. It's easier to find room for smaller diameter headers.  

Thanks for the concise answer.  The concept of inertia of the gas flow makes sense for what I see termed "scavenging" in these types of discussions.  It never occured to me that a wave travels back to the valves and might interfer with gas exiting the exhaust port in the head.  This must be what I see referred to as "regression" in some discussions.  I work a lot on water wells and associate with engineers who do "surge analysis" of water transmission lines, analysing the same type of back-and-forth wave action in a pipeline when a valve opens or closes.  Their goal is to make sure the "water hammer" doen't break something in the pipeline.

You have added a new variable (to me), namely, primary pipe length.  Now the combinations and permutations get staggering.  Presumably, too large a pipe results in loss of inertia and scavenging, too small a pipe results in excessive friction and restriction of exhaust gas flow, and the wrong length of pipe results in wave interference at the gas port.  It appears that to check this out emphirically, one would need to run a number of experiments on a dyno using a number of pre-determined header designs.  The costs would likely be enormous.

Is this why addition of a large-diameter collector is important?  Something has to generate the regressive wave.  If you exhaust directly to the atmosphere at the end of the primary pipe, the timing of the wave should be controlled mostly by the primary length, as you already pointed out.  This must be the basis for "tuned" exhausts.  Evidently, the next best thing to exhausting to the atmosphere is exhausting into a large-diameter pipe, i.e, a collector.  This would be because you are now trying to cram exhaust from two primary pipes at a time (or four at high rpm) through the collector or exhaust pipe; therefore, it seems to me that you simply want to increase the header and exhaust pipe diameter to flow the same volume of exhaust as is coming in from the primaries, and make that flow velocity the same as the velocity in the primaries.  Eventually friction in the collector and exhaust pipe will make this impossible, but by then the distance to where the regressive wave is generated should be so far from the exhaust port in the head that the regressive wave is very weak.  In effect, the collector should have the same effect as making the primary tubes longer.  Does this make any sense?

If the above is conceptually correct, I still don't have a clue how to use it in a practical sense except trial and error experimentation.  I would be curious about the equations, but working with vapor, which is compressible, is a lot tougher than analyzing surge in water, which is essentially incompressible.  My guess is that the equations will have some inherent limitations due to the latter problem and the unexpected results of localized turbulence in the exhaust system which will likely be unique to each and every system.

I am still at least a year out on putting my project together (still building a house first) so would be curious to hear the results of your experiment with the 1-3/4 inch headers.  Considering all the above, it makes sense that engines using a supercharger will need larger primaries simply because they will flow more air than an engine without the supercharger.  However, the loss of torque at the low or mid rpm range may still be an issue since the largest flows through the heads will not occur until the higher end of the rpm range.  Like a lot of things, this looks like an issue of timing and compromise.  The question is, when are we starting to split hairs over very small factors, such as a small loss of exhaust flow at lower rpm, versus causing a large loss of low and mid-rpm performance trying to squeeze that last bit of performance out at the high end?  Life would be simpler if we could run at wide open throttle.

Let me know how your headers work.

Mike K

        I didn't explain some of this very well. The object of varying the length of the primary pipe is to return the negative portion of the wave just as the exhaust valve is closing. Theoretically this aids "extraction" of the chamber. The wave is returned from the end of the pipe by bouncing off  atmospheric pressure. Or in the case of the collecter, from there. Obviously that will only happen over a limited rpm, or in multiples of that number. That's why street headers are longer than race versions. Actually, on the street, the Tri-Y  or 4 into 2 into one thing seems to work. It all changes when you run mufflers and tailpipes too!!

      Collector size seems to also be trial and error, with smaller/longer helping low end. I don't think there's and exact correlation between the total primary area and the collector area. Don't forget, the exhaust gas cools as it travels down the primary, and less heat equals less appearant volume. So the collector is smaller than the total of the primaries.

Edelbrock published some interesting formulas about 15 years ago, when they got into the header business. There's also  a couple of very good books on the subject. One by Phillip Smith, called "the scientific design of exhaust and intakes. ca 1960. Chrysler did a lot of work and published some of it around the same period. (SAE)  And of course the motorcycle guys have done LOTS of this stuff, starting back in the '30's. They make more power per cubic inch without blowers than we do with them!    

I think I'm getting a headache.

At least two things are becoming clear to me based on these discussions.  One is that there are so many variables involved, I can see why trial and error has been the most practical approach for those of us without the resources of GM or Ford.  Second, it appears that any specific design is likely to work best within a fairly narrow range of rpm, where the timing of the waves traveling back and forth in the exhaust work best, or in other words, for a specific application, say low end torque versus wide-open throttle performance.  That is where the information obtained by trial and error becomes valuable.  Does that information compare favorably with any general guidelines resulting from the research in the various books?  I will try to find the references you mention.

I'm not sure that after the initlal improvement over stock exhaust systems and some choices about what range of rpm you want the most improvement, we are not getting to a point of diminishing returns worrying about this.  Obviously, getting the headers to fit the car may be a bigger constraint.  After going out and looking at the Fairlane 500 I am using for my project (I haven't worked on one of these since about 1968), my headache is getting worse looking at all the stuff in the way on the driver side.  It makes one appreciate what Jerry Christenson has been dealing with, developing some good headers.  I have a 57 convertible at my farm about 200 miles from here that my brother put Hooker headers on back in about 70 or 71.  I will look at it next time I am up there and see what they look like.

Thanks for all the input.  It gives me a lot to think about.  A final question that I am now just starting to frame, based on all this, is if a lot of the performance of the headers is based on the timing of waves in the exhaust gas, the factors determining the frequency of the waves are the controlling factors.  If this is the case, those factors might not be sensitive to primary header pipe diameter, i.e., the same timing of the waves might be obtained over a range of header pipe diameters.  Then we would be back to the issue of how large we can make the header pipe diameter without loosing inertia and effectiveness of the complementary waves forming in the exhaust system.  Presumably, a Y-block with a supercharger would then accomodate a larger diameter primary tube than a normally asperated Y-block, which is consisent with Ted Eaton's observations in an earlier reponse to my questions that engines with superchargers seem to follow a different set of rules.  Accordingly, an engine with a blower might use larger diameter primaries and still have low and mid-end torque, if the lengths of the pipes and collectors are properly sized.

This gets us back to gas flow and volume.  The arithmetic to determine the volume displaced by an engine at a given rpm is fairly straight forward.  However, the true volume will depend on the pressure of the gas passing by the intake valve, since air is compressible.  How much does that volume change when you increase the pressure to more than atmospheric pressure with a blower?  I think I also have that math, but it must be taken into account.  Well, I am starting to spin my wheels here.  I appreciate the insights and think I will go off and contemplate something simple for a while.

If I can find an affordable dyno in my area after I build my engine, I will probably try to get some different headers and do some experimentation.  For example, I could buy some pipe and build some headers with different diameters and lengths, not made to fit the car, but simply to experiment with some of this stuff on the dynol  I would need a dyno shop that would charge on a daily basis for multiple runs instead of a high price each for a few runs.  Seems like a lot of trouble for probably less than 10% gain in horsepower, but maybe worth it if the overall torque and horsepower curves are improved to eliminate some weak areas.  Mostly, the whole subject had piqued my interest, but I need to find out more so I don't spend my time duplicating something that someone did 25 years ago.

Mike K

Found the book you mentioned on Amazon plus a lot of other stuff on exhaust systems and supercharging.  Some hints that exhaust design for superchargers does not follow same rules as without supercharger.  I ordered five books so will keep myself entertained for a while.  Probably could have bought half a set of headers for the same price.  I don't know why I get off on these technical tangents.  I grew up on a farm where if we couldn't fix it with a hammer, we figured it was probably an electrical problem.  Seriously, I have wanted to study this type of stuff for years, but too busy working and raising a family.  Hopefully, studying some of this will make me more practical, but informed practical.

Mike K

      I think the diameter of the pipe correlates with the volume of gas. With the supercharger adding to that the increase would be directly proportional to the increase of air fuel in the cylinder. All kinds of variables eneter the picture there. How much boost, how good are the heads (what do they flow) cam timing, what rpm range do you want to use as a basis?

          I'm taking a conservative approach at 1 3/4" because I have a relatively mild engine. Pure stock actually, and I won't change that so it would still be legal with manifolds on. I do know both Ted and John Mummert have discovered the Y's like big primaries. Possibly because the exhaust ports aren't great in the iron heads. The hp numbers I'm making would dictate an 1 3/4 or bigger, (1 7/8") primary. I don't want to chop the car up for fender wells, so I'll build a shorty at 1 3/4 and see what happens. No math, just a guess and a  welder.

Charlie,

         This is strictly a guess, but I'd imagine for clearance more than any other reason. It couldn't hurt the flow much either. They actually work pretty good for a 50 year old cat iron manifold. And, Hedman did follow that pattern with their early designs, but the pipes were too small. I had a set on at Columbus this year.   

Thanks for the pointer.  I was giving that some thought already.  I notice that the tri-Y headers I have reviewed do not seem to attempt to match up the cylinder firing order.  My understanding is that the tri-Y setup doen't work that well over 3500 rpm anyway.

You are the first guy to mention that you have done some dyno work on your headers.  Do you have any data that would suggest the idea that primaries bigger than 1-5/8 will cost me low end torque on a 331-cid Y-block with 10-12 inches boost at the blower and about 5-6 in the manifold?  Or is this a carry-over idea from engines without blowers?

My heads are ported and I am using big valves (see previous message for details).  In other words this is a Y-block with as good of air flow as possible by porting out the cast iron heads.  I would be curious what your dyno data for the 2-inch pipes indicated at low and mid range.  Of course the cams will probably be different, etc., but if nothing else in your engine and cam design should limit low end torque, I wonder how the 2-inch headers performed.

You will probably get this done before I get started so would like to hear the results.  Are you checking this on a dyno?

If I can work out a deal on an affordable dyno, as I mentioned yesterday, I would like to start out with some long header pipes, making several diameters, and experiment by cutting back the lengths until I see if things are getting better or worse and where the best resuts occur.  Then I would experiment with adding collectors of different lengths.  I would not be trying to make these to fit a car, only to experiment with to see how headers work on my particular engine.  Like you said, some pipe and a welder.

I am in central Montana, so need to do some research on the closest engine dyno facility that might work with me.

Mike K

It sounds like 1 5/8" primaries on a supercharged set up will be alright for about 485hp.  That's what Hoosier has.  I wonder if he's pondering larger primaries now?

If you have the equipment, and a track close enough, you can go to test n tunes and do the same testing for the headers, probably at much less cost.  You can make the headers variable length and keep making runs until you figure what works best.

This is how our Twin turbo headers looked at the Phase One set up.

And this is how our Single turbo headers looked at our Phase Two set up.

The Phase Two gave us 330 hp and 465 ft lbs with that too small Rajay turbocharger wich generated over one bar of exhaust back pressures to slow down our engine.

So, use what you can get to fit as an headers, and they will work with enough boost onboard

   Mike, no, quarter mile times and ET's. I'm not going to pull the engine oe spend money for dyno time at this stage. We did that when I picked the motor up from Mummerts. I can tell you this, we tried a set of Jerry (Christianson's) street rod headers on the motor. They were too small and WAY too long for this motor, but it picked up 50 ft lbs at 3200-4000 over the manifolds! 

I haven’t performed dyno testing specific to header tube sizes on the Y but do have it planned in the near future.  Collector length testing has been easy enough to perform but doing the various tube size testing requires headers for each tube combination; the lack of headers representing all those combinations has been the hold up for that.  For the FE’s, I’ve been able to experiment with tube lengths by having a removable collector and using extensions of various lengths to extend the overall tube lengths.  I am slowly collecting Y headers of different configurations and will simply test all these on the same normally aspirated mule engine when time permits.  The problem with this kind of testing is that it will find the optimum header combination for the engine being tested which will not necessarily be the best header design for another engine if any of the engine parameters such as displacement, compression ratio, camming, rocker ratio, head work, intake manifold, etc. changes.  If it was definitive, there would be a single formula saying what the header design should look like but there are simply too many variables.

This tells me quite a bit because you indicated earlier that you are running a motor that is essentially stock.  I presume it is not supercharged either.  If your motor needs more flow through the headers, I probably will need even bigger headers with the supercharger.  What heads are you running and are they stock valves?  Stock cam lift and duration? Are your heads ported?  What size carb? I just wonder how your setup compares to mine.

Mike K

I thought that if I tackled the dyno testing with various header tube diameters, I would not try to find existing headers, but simply fabricate some generic headers for the tests.  That way, I would not have to worry about making them fit the car body.  Your idea about different lengths of extensions makes more sense than what I was thinking (a Saws All) and would preserve the header tubes for collector experiments.

I agree that the data would only show what that particular engine liked, but some generalizations and extrapolations could be made.  If you ran the tests on a normally aspirated engine and I ran them on the supercharged setup I am building, the tests would provide a range of data that might be extrapolated or interpolated to other engines.  At least some principles might be established.

I have no experience in dyno testing.  How much effort does a run require, once the engine is plumbed in and connected?  Is this a readily repetitive process (assuming the engine is running ok) or is there more to be done between runs than changing the headers?  I am guessing you have a dyno in your shop.

Mike K

      It is blown. It's a reproduction F code, using 471 heads. I built a repo intake from a standard B manifold, uses an Engle cam with Ford blower cam lift and duration figures.

     The motor made 377 hp on the dyno in California. The motor was built by John Mummert in 2003 or 4.  So far the best times have been a 13.70 at 105 mph through the mufflers on 215 radials in pure stock form (calculated to be 344 hp to the rear wheels) and a 13.55 @ 105 on slicks at EXPO this year before I broke the retaining straps on the driveshaft by leaving at 5000 rpm. I built the car out of curiosity, wanted to see just how strong the 300 hp F codes really were. The answer is pretty Dang strong for 1957! The car is at present a three speed column shift with 4.56's on the strip, 3.25's on the street.

I do have an in-house dynameter and once it’s initially set up for a particular engine family, it only takes about 40-50 minutes to get an engine in place, plumbed, and ready to run.  After being installed on the dyno, it’s essentially like starting the engine in a car and running it through its paces.  On a new engine, the camshaft can be broken in while also simultaneously loading the engine to seat in the piston rings without concerns of any overheating as the dyno’s engine cooling system is constantly refleshing itself.  An actual full throttle dyno pull on an engine will typically take no more than 14-15 seconds maximum and can be shorter depending upon the testing parameters.  The accuracy of the dyno being used will dictate exactly how many pulls must be made per combination in order to get statistically valid results.  My particular dyno is repeatable to within 1 HP between pulls providing that the water and oil temperatures as well as atmospheric variables are kept consistent.  In my case, this means very solid data from a single pull without having to average data from multiple pulls.

In regards to testing header designs, just changing out the headers from pull to pull should suffice without doing a full range of carburetor and ignition timing variables in order to evaluate them.  But on my end, I can also monitor BSFC, air/fuel ratios, and exhaust gas temperatures and if these are changing radically during header changes, then it does point to timing or carb adjustments being required.  Where scavenging is being optimized, then timing and carb adjustments should be revisited anyhow.  And then the question comes up whether to test in an open configuration or with a full exhaust system.  And if with a full exhaust system, then a multitude of other variables crop up such as tail pipe size and length and which mufflers are to be used.

And in total agreement on the interpolation/extrapolation of data.  Trends do become evident when examining the data which then permits additional testing to head off in a more defined direction regarding changes.

        No, just a list of the good and the bad. If, like Ted, I had a dyno in my back yard, it'd be busy.

This is just what I wanted to hear about a dyno.  I been told some horror stories about trying to use dyno shops that really don't know what they are doing, but suspected that exactly what Ted is saying was possible.  I have always wanted to use a dyno, but never had the money or place to do it.  I need to get my engine together and do some long-range planning.

I appreciate the comment about sonic testing.  It is essentially a standard procedure at the machine shop I use.  They are really big block Chevy guys with one guy who has Y-block experience.  They quietly turn out racing engines for a lot of guys in this region and typically work on $65,000 to $100,000 engines.  They have some funny ideas about timing older engines retrofitted with a blower (they think blowers make engines run hot, so keep retarding the timing and locking it in with no advance capability in order to prevent detonation - gee, I wonder why they run hot), but they do very good machine work.  I go to another shop for grinding the cranks so they don't grind off the oil slinger with oversized hones.

I will try to start assembling an engine while proceeding with my house, just as soon as I get a roof on things including the garage.  I have the crank ground and the heads ported, but no work done on the block, decking the heads, ordering pistons, or anything else, other than piling the bearings and h-beam rods in a box with the block.  I guess I had better at least order some more parts to add to the pile and finish my research on the cam.

Thanks for the ongoing tips, comments, and advice.  I will keep you posted about my progress in the future, with the goal of doing some dyno testing before finishing this project.

I am finishing a big project at work and then off to Arizona next week for another project, so may not be in communication for a week or two.  If I don't reply to anything on this forum, it is not for lack of interest, but because I am tied up on other stuff for awhile.

Mike K

Wow! If I remember some of the stuff I have read about the F-code setup, you are exceeding stock performance by quite a few horsepower.  Do you think a guy could duplicate your performance using an e-code repro?

I have a couple of cars besides the current Fairlane 500 for this blower project.  One is a Custom 300 with a 3-speed and overdrive powered by a 312 that my brother rebuilt in about 1969 or 1970.  I don't know what he put in it, but it is probably a good engine to rebuild again.  Back then, we were always told not to bore over more than 0.060 inches, so our blocks are still generally good if the main bearing webs aren't cracked.  I don't know the rear end either, but assume it is stock.  I bought the Custom in 1966 for $127 when I bent up both doors on my Fairlane 500 and was crawling in and out of the windows.  I drove the thing from Montana to California and then up to Seattle before giving it to my brother when I got a 57 wagon which I also still have.  It has a 4.10 or 4.11 rear end and a thee-speed and overdrive.

I have two or three e-code manifolds, but only one set of really decent tea pot carbs that I have on an Edelbrock 257 manifold on my brother's old convertible.  I was thinking that I might come close to the type of performance you describe above if I use the Edelbrock 257 manifold or port out an e-code manifold.  I could also make life simple and put a good modern carb on one of the Blue Thunder manifolds from John Mummert.

All my heads are 57 312 heads so I will be dealing with relatively high compression, depending on how I build the motor.  In the late 60s and early 70s, we put in domed pistons with high compression and added aviation gas to the fuel.  Those y-blocks would tear the splines off a normal 3-speed Ford transmission, but worked good with a top loader.  I have no idea what horsepower they made, but they were pretty ferocious and would beat most of the cars in that era, including some of the 409 Chevy Corvetts.  We used either stock exhaust manifolds or Hooker Headers.  I still have one set of the Hooker headers on a 312 in a convertable.

Our engines tended to blow up fairly early in their life, but we weren't babying them.  The main problems were thrown push rods and scuffed cylinder walls and cracked rings from the aluminum pistons heating up (as well as from detonation if we tuned them wrong) plus burnt valves because we could not afford stainless valves or stelite or stainless valve seats.  When we weren't adding av gas, we added a little diesel or kerosone to the fuel to keep them from knocking.  We probably did not have enough expertise to know how to build those motors properly, but they would work good for quite awhile considering how hard we used them.  I am not sure what kind of compression we can run now with today's gas, so that will be another area of inquiry from guys like you when I get this first project done.

I don't know if my 312 heads are posted or not because I haven't had them off the cars for 40 years and didn't know posts existed back when I worked on them.  If I ever get this blower project done, the next one will probably be to fix up the Custom 300 as an e-code repro and see what kind of performance I can get using either some tea pots or some of the WCFB's I have.  The latter are in very bad shape and not the original dual quad setups, but have the small carb base for a Y-block intake.  These are all thoughts for the future.  I need to concentrate on the blower project right now but want to try a normally aspirated engine project in the future.

Mike K

One thing starting to emerge from this research is that exhaust requirements for supercharged engines are not the same as for regularly aspirated engines.  Most of the info out there does not apply to supercharged engines.  The book by Corky Bell provides a lot of formulas, which when I compare them to the results of published dyno tests in some of the magazines, including Y-Block Magazine, appear to work fairly well.  In general, the advice about supercharged engines is that bigger is better, but when you start crunching numbers, the objective with the header primaries is to make them big enough that rate of gas flow does not exceed about 250 fps.

Ted Eaton, earlier in this thread, reported good results on a drag racing application with 2-inch primaries.  In a detailed conversation with Jerry Christenson, he thought 2-inch primaries would be big enough on a supercharged, 331 cid Y-block with ported heads.  Gord McMillan has got good results with 1-5/8 primaries on mildly boosted engines like I propose and did not think I should go bigger than 2-inch on the primaries and 2-1/2 on the collector and tailpipe because I might loose low end torque.

When I worked through all the formulae in the book by Corky Bell, the results indicate that for my application, 2-inch primaries are what I should use for the predicted exhaust gas flow under boost at maximum rpm.  As Ted Eaton pointed out, these designs are unique for each engine, so what applies to my engine may not apply to another.

Based on the foregoing considerations, my header design should be simple, right?  Well.....maybe not.  I am using a centrifugal supercharger which does not even begin to make boost until 3200 rpm and peaks at 6200 rpm.  Accordingly, the engine may act more like a normally aspirated engine until boost starts to come up.  The question is, how much effect does the header design have at the lower rpm's?  Some of the stuff I am reading says none at all, just get rid of all the back pressure, other stuff says low and mid-range torque will be effected by header design.

Here is what I see emerging for my application.  First, the cam design will have the most influence over torque and the range of rpm where maximum torque occurs.  I am not sure to what extent the historic experience offered about header influence on torque may have been influenced by cam design.  Secondly, if I do not have any backpressure or it is less than 0.5 psi in my exhaust, I don't see wave forms and exhaust gas inertia having all that much effect, in other words, if the pressure stays so low as to be hard to measure, that indicates that gas inertia and waves in the exhaust gas are not interfering with the exhaust process.  However, thirdly, part of the exhaust gas theory is to try to create a negative pressure at the exhaust port just as the valve opens.  Accordly, low measurements on a pressure gage don't mean zip if you are trying to measure a negative pressure, so the pulse and scavenging theories may have some value, particularly at no boost or low boost.  Fourth, (and I am waiting for some back ordered info on this), the length of the header primaries effects the rpm range where the torque occurs, assuming the pipe diameter is matched to the gas flow.

In summary, it looks like 2-inch primaries are big enough for my supercharged y-block.  The cam design will be a lot more important than anything else.  I will still design the header primary pipe lengths to maximize low to mid-range torque, so far as the exhaust goes, recognizing that the supercharger will have more effect than anything at the higher rpm where boost increases.  The latter principle will also apply to the cam design, it does not have to be too radical for the supercharger to do its job, so long as I have been paying attention to maximizing airflow through the head.

That is about the extent of my progress on this question to date and I appreciate all the input you folks have provided on this.  If I learn anything more, I will add it to the thread.

Mike K

Regarding your January 3 comment about 1-3/4 pipes for your mildly supercharged car, the gas flow calculations in Corky Bell's book "Design, testing and installation of supercharger systems" will let you make sperate predictions about the primary pipe size and tailpipe sizes required for your application.  Without doing the calculations, but considering what I have been reviewing, my guess is you will find 1-3/4 inches is plenty big.

The other thing the experts writing these books say is that short primary pipes are appropriate for wide-open racing applications because they shift the torque curve into the higher rpm's where more power is generated.  This may not be the way to go on a street car because you will be weak on torque in the low and mid rpm's.  Again, this will all have to match up to your cam design and where it generates torque plus what you intend to use the engine for.

If I am understanding what they are saying, primary pipe diameter has to be sized for gas flow and probably does not affect anything but potential backpressure and restriction on the exhaust.  However, primary pipe length may have an effect on the range of rpm where torque occurs.  Evidently, with enough supercharger pressure, the latter effects may go away.  For those of us using relatively mild boost superchargers, the length of the header primaries may still be important (my interpretation) until our supercharges start to generate boost at the higher rpms.

Mike K

Just one test, but gives you an idea how this particular engine responded to different headers...

Thanks for the article.  According to everything I have looked at since starting this research, 1-5/8 inch headers are more than adequate for the 5.0 liter engine.  Unfortunately, the dyno tests simply do not show enough difference between the two types of headers to support a conclusion about the effect of one versus the other.  The lack of good response to either set of headers tested suggests to me the test engine was affected more by air flow limitations in the intake manifold and/or heads than in the exhaust. 

Mike K

Guilty as charged.  I did not auction the Sunliner or any of my other 57 Ford cars.  The Sunliner sat out in the weather from 1971 or 1972 to 2000 so is in tough shape.  It had a crunched front end when it was parked and when my brother first bought it, it had thick layers of Bondo on the rear quarter panels and bad rot in the rockers and lower quarter panels.  It is currently stored inside, pending a major restoration project.  I have been too busy the past four years to start the project, and had a chance last year to buy a Fairlane 500 hardtop like I had in late highschool, so got diverted into putting that together with a Paxton blower setup, more or less the car I would have liked to build back in the 1960's, but could not afford.  The hardtop does not require nearly as much work as the Sunliner.  I will probably start work on the Sunliner in a few more years, after I finish a house building project and separate shop that are currently under construction, with me doing most of the building.  It takes one guy a long time to get this kind of stuff done, so the cars are on the back burner.  In the meantime, I continue to collect parts for the hardtop and the Sunliner, expecting to complete both cars in the future.

The auction four years ago did go well, with more than 125 cars and pickups sold.  I still regret having to sell some of the older cars, including a 57 Chrysler Imperial that was still road worthy, but a guy only has so much time to do things at my age and there was no point in letting them sit and rot and/or be vandalized.  I still have four complete 57 Fords and an additional two parted out bodies plus several extra 312 engines, so I have plenty of work to do on y-block projects in the future.

Mike

Mike,  I'd honestly be amazed if the E code made as much power as the F code. Check Vic Correnti's 'Bird though, it's an E code, 4 speed. Oh......yea, with a 250 hp nitrous setup!!