I have a BT on my bird right now and I have had a ported iron B.  Mine is a reasonably built 292+.060 with Headers and hotter cam.  I did not see much if any seat of the pants improvement with the BT.  On this car i am assuming ex manifolds maybe even the small '56 ones and stock exhaust system with 1.75 tail pipes.  If so my take on this engine is threefold:

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.

Doug T

The Highlands, Louisville, Ky.

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!!

Ron Grove

Wauconda, IL

ron, i was watching that manifold too.. keep your eyes peeled for other outlets for B manifolds as it seems they are starting to fetch some pretty crazy prices on ebay.. you can tell cause some people are listing them with a STARTING bid @$250.. I was patient and finally it paid off and i wasn't bent over a barrel for it..

Dustin

Southern Oregon Y's Guy

http://www.facebook.com/?ref=home#/profile.php?ref=profile&id=1441322018

yup, poor choice of words on my part referring to it as "sloppy"!  Sorry about that!

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.

Ron Grove

Wauconda, IL

Based on what I've read, yes I think the B manifold will improve the low end but I have not used both intakes on the same engine and do not know first hand. The 500 cfm carb should be adequate. You will have to open up the bores of the B manifold to maximize the potential. Otherwise, the carb will not be allowed to flow 500cfm.



But because you have already installed the BT, I think many us are offering ways to improve upon the problem you have stated in a more cost effective manner. I really think that your vacuum should be higher which indicates to me that the tune is not quite right. When it is right, your low end and probably upper end should improve. Also, ensuring that it's tuned well will allow time for Ted to finish dyno testing and have a conclusive answer about the B vs. BT!



Improving your low end could be as simple as a Carb swap. I changed from an Edelbrock 600 to a Holley 570. I don't plan on using Edelbrock again.


Lawrenceville, GA

Thanks!  I guess somehow I gave the wrong impression or something.  It isnt really poor low end performance today.  The question was more along the lines of would it be better with the different intake if that makes sense.  If you drove the car, there wouldnt really be any noticeable shortcomings, but if it can be improved, thats what im looking for...does that make sense?  Car isnt stumbling, bogging, no flat spots, etc....I hope that makes sense...

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!

Ron Grove

Wauconda, IL

There may be other issues with the poor low end performance you report. However, on your question about the Blue Thunder intake, I've seen two Dyno tests on smaller Y-blocks that indicated that the Blue Thunder hurt low end torque. In one case the BT didn't catch up to the "B" intake until 3100 RPM.

Paul

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!!!!

Ron Grove

Wauconda, IL

When I had a damper rebuilt the damper doctor got it way off. Had to have it remarked to get timing right. you can look down onto the damper and see the wide spokes, the damper has 3 of them. If the marks are off a little check the spoke where the timing marks are and mark where the center of the spoke is and that will put you on approx 12 degrees, your damper may show you that if it's right.

-Gary Burnette-

I think your vacuum should be somewhere around 15" or better. If you didn't determine where TDC is during assembly, then don't assume the rebuilt damper is right. Play with your timing, make sure your idle adjustment is right and that the carb is generally tuned well.

What are you running for ignition? Upgrading the ignition system may help and doesn't have to be too expensive.


Lawrenceville, GA