Car is a 56 Sunliner w/a 292, FOM, with blue thunder intake and (currently) an edelbrock 500 carb.  Dizzy is a '57 type w/pertronix.  Cam is from mummert - 224 duration at .050 lift for intake & exhaust, with 110 seperation.  (grind number is 270-3; bought it from mummert per his recommendation)

Issue that Ive been struggling with is a sloppy low end throttle response/lack of torque.  I know some of that is the cam, but after doing some reading, and based on some new tests, etc (i.e. Teds research/thoughts), Im starting to seriously wonder if Id be better off with a different intake?  Most opinions seem to be that the blue thunder makes less TQ than a B manifold below about 4k revs or so, if im reading info properly.  Problem is that with my FOM, my car hardly ever sees over 4k, even under WOT.  So Im wondering if Id increase around town driveability if I went to an OE "B" manifold?  I know that John M is working on a new Blue Thunder that is supposed to be better in the low end, but I havent seen/heard when that will be available....

Other question is if I should be running a bigger carb...with either manifold.  Also, if consensus is that a B manifold is better, what is a reasonable price to look for?  And woudl it have to be bored out for use with a holley or edelbrock carb?

Thanks to any and all for constructive thoughts and help!!!!

Intake is kind of the last part of the equation that I havent experimented with until I saw diminishing returns, so Ive been doing some digging and figured Id ask the question.  Based on what Ive read, I cant help but think that a B manifold with the edelbrock wouldnt provide better low to mid range torque.  But I guess im not sure if it would be noticeable, etc....or if its all in my head.   I have a tendency to waaaaayyy over analyze things!

?

And yes, Im familiar with FOM weird 1st gear programming (now THAT would be a great mod/change!  Figure out how to get it to start in 1st EVERY time!!!!)

WHen I was messing with carbs over the summer, IIRC, vac was around 12.5 in gear at about 500 revs at idle.

Someday if I ever get around to either rebuilding this engine or putting together a higher performance oriented mill (better heads, higher CR, etc.) Ill use a different cam, etc.  And at that point Id consider a different trans, too....but that is all a looooonnnngggg way off, if ever.

Thanks!

Im as sure as I can be without a degree wheel.  Used a service manual and eickmans book during the rebuild.

Again, the car isnt terrible; just trying to see if there is a way to get it incrementally better....

Thanks!

speedpro56 (1/24/2010)

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rgrove, You should be ok with the cam you have, it's for a stock converter. The BT intake in stock form should be ok as well with an average of 264 cfms per runner. The BT intakes we're running are considerably higher in cfms than the one you've got. Set the timing 12 too 14 degrees GET a smaller carb in the cfm range of 390 - 410 and see if that want make a difference. That's a LOT cheaper AND alot quicker than pulling out a mild street cam.

Actually, my car liked even more advance than that as a base.  However, I backed it off to 12 degs because the exhaust is so loud I was afraid I wouldnt hear pinging, although the plugs looked decent.

Ive messed around with a holley 390 carb.  It was a little better, but had much less as the revs climbed than the 500 cfm carb.  Bigger carb just worked a bit better.

Im not sure i understand your comment about "the BTs we are running are bigger"....  I think I was one of the first ones to get one (around 2002, IIRC); have they changed over the years?  Or have you done additional work to yours?

Thanks!!

If the camshaft was not degreed in when it was installed, then that will remain a question until it is degreed in.  Simply counting the pins between the marks doesn’t classify as degreeing in the camshaft.  However, installing a 2” four hole spacer under the carb will improve the vehicles performance right off of idle with the Blue Thunder intake.  Have you checked the manifold vacuum at idle?  That will give a clue as to look at the camshaft or go elsewhere.  Something else you can try in the short term is add 0.003"-0.004" of clearance at the tappets and see if this improves both the manifold vacuum and the off idle acceleration.

If the car responds positively with more intial timing without any signs of detonation, then run it there for awhile and see if that’s where you’d like to leave it.  If you haven’t checked the damper lately for an exact TDC mark, then there’s always the chance the damper has slipped which is leading you down a false trail.

Thanks for the replies...  Manifold vacuum at idle is 11.5" @ about 500 rpms.  I will try tightening up the lash a teeny bit too, but the issue im trying to improve upon has been existant since the car got on the road, so...

As for the damper, I had it rebuilt last year, so it should be good for timing marks.

And Ive thought about a spacer, but Im reluctant to use one....Im pretty sure it wont fit under the hood.  I have the BT intake, with either the holley or edelbrock carb, and I am using a gutted out oil bath air filter, so it takes up a LOT of height under the hood.  im just not sure I could move everything up 2" and still close the hood.  We show the car a lot, so I dont want to ditch the air filter assy.

Originally, I was thinking of putting on a demon JR 525 to clean up some of the response over the edelbrock.  More research, however, led me down the path of thinking I could improve with a different manifold first, see how that works, then try the other carb if needed; a lot of variables........man, I wish i were smarter!!

Ok... when i got the damper back from damper Dr, i looked at it as you suggested.  It "looked" good.  Obviously I havent taken the engine apart to confirm, but....

I understand (and truly appreciate) all of the other suggestions related to timing, valve lash, etc.  However, Ive been through all of those other components many, many times (with the exception of changing valve lash specs).  Assume for this question that all else is in reasonable enough order....
So the bottom line question remains, based on the expertise on this board, am I likely to pick up noticeable low end torque with a B manifold?  Thats what Im trying to get to.

Thanks!!!!

Id be curious if anyone had a dyno sheet of the BT vs B intake to see how much TQ difference there is below 3k revs, and how much is gained and what the slope looks like.  Is it a significant TQ difference, or only a few ft lbs?  In other words, would it be noticeable in my application?

Ive seen a few B intakes on ebay for just over $100 or so.  Just trying to figure out if its worth it to experiment...

THanks again!

On carbs, I think in hindsight I never would have bought an edelbrock.  I got it because it was the only one at an even 500 cfm.  Certainly not as tunable as the holley 390 I experimented with.  Thats what got me thinking (on a seperate note) about eventually switching to a demon jr 525.

And as for waiting for the dyno tests, I should probably wait, especially since the car will be in storage for another month or two at least.  I was just getting antsy because there was a B manifold on ebay that was going for cheap....but I missed on it anyways.  Should also probably talk to mummert about the new BT and results on that one vs. the original.

Thanks! 

Ron.

Yeah, I saw that.... that guy is NUTS.  $250 seems a bit salty for a B intake!

Patience is a virtue that I certainly lack!!

1 It isn't big enough and with the FoM has too much inertia to get the column of air&fuel moving quickly when the throttle is opened.

2  The velocity in the BT runners is too low to keep the fuel suspended in the air of the intake charge. 

3  The exhaust can not help scavinge the cylinder to accelerate the charge through the head.

I would be tempted to try a '56 4bbl manifold ported to match the carb with an adaptor to the modern pattern.  The runners are slightly smaller than the B but probably a better match to the engine.  I don't think the 500cfm carb is ideal but it might not hurt with the smaller manifold. If you still have the '56 manifold this might be a quick and easy fix.

BTW I think that Ted was suggesting that you add about .003" to the specified valve lash, for example if it was .018" set the valves to .021" instead. This has the effect of reducing the duration of the cam somewhat which should increase vacuum. I would check with John M about this idea but it is likely that you would still be on the clearance ramps of the cam and no damage would result.