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Well spotted Sizzler ! Is that PSE base to adapt a short deck BBC manifold to a tall deck block?
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carnut,
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http://www.gmgoodwrench.com/perfpart...0850_large.jpg http://www.mopartsracing.com/parts/blocks/hemiblock.jpg |
craig,
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Steve |
Sizzler, I'm interested in that FE manifold base, how much or, does P.S.E. still make it?.
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Perry,
As far as I know, PSE does not exist any more. I would suggest you grab that one if you feel you could use it. Steve |
My book "How To Hotrod Big Block Chevys" Supports the flat torque curve explanation of the unequal stacks. It says the Can Am people were the primary users. The drag racers were shooting for peak HP thus they did not use that config. Nothing is said about the cooling effects of port pairing (although I would think that is true) nothing is said about port config being dictated by head bolt config.
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The staggered stack hights were definatelyto tune for the long/short intake runners of the standard BBC head. This was especially critical for individual runner intakes like the FI units shown. Many BBC single 4 and tunnel ram intakes of the day had the carb pads "twisted" in an attempt to equalize the runner lengths.
I read an interesting article in which one of the GM engineers that designed the BBC explained how the Z-11, or "mystery motor" of '63/'64 was built with equal length runners and 5 head bolts per cylinder. To do this required more complex tooling/casting procedures and a higher rejection rate and IIRC different intake and exhaust rocker arms. The "bean counters" at GM nixed the plan and told them to design a head that cost less the produce and to use the same rocker arms on the intake and exhaust. They were able to keep the 5 head bolts but had to compromise the intake port design for cost sake. BTW, The ZL-1 does have a head bolt that passes through the intake port. The hole is then plugged with an allen plug. --Mike |
Steve, I got my information from a chevy high performance book, that had a 3-5 page article, actually interview with the engineer that designed the mark IV BB, and he talked about the designed aspects, the reasons why the Mk II and MK III BB engines didn't make it into production, and then finally the MK IV, and reasons why it was designed the way it was. If I can find the article, I'll either tell you the source, or maybe send you a copy of the article.
Just from visual comparison, I can tell the volume difference caused by the difference in stack height is much greater than the volume difference between the small and larger ports in the head. In addition to the volume difference between the ports, I believe there was also, and I think more importantly a flow difference that affected VE and maybe fuel distribution, but Maybe I'll look that up, not that it makes a big deal to me. In other words, I think the reason was for the fatter torque curve as others have stated, and not so much for the slight difference in port volume. |
427S/O Henry send me a private e-mail for what you are loooking for. I have the info for PSE. Rick Lake
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http://images.amazon.com/images/P/15...CMZZZZZZZ_.jpg I stand behind my explanation of different length stacks on IR manifolds for the BB Chevy. If anyone is interested in Chevies (gasp!), I suggest the Performance Related forum.http://www.chevytalk.org |
Carnut,
Copy that. 6 bolts instead of 5. I think if someone put all of us together, we would make about 1/2 a Chevy guy.:p Steve |
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