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I have Berg (Weber) 42DCNF carbs with velocity stacks.

I have ordered Aluminum Pressure Covers (turbo hats).  They may be shorter than my air cleaners reducing space above the velocity stacks.  What should be the space above the velocity stacks?

If I don't have the needed space I could get the Type 3 stacks that are shorter or add a spacer under the turbo hats.

1957 CMC (Speedster) in Ann Arbor, MI

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I ran the standard $6 CBP velocity stacks with my turbo-hats for several years. I always felt like they were too close to the underside of the hat tops, but I never noticed any degradation in performance.

I'm setting up the new engine for EFI and just last week revisited the stacks. Now that it makes almost no difference, I located and purchased shorter (30mm, if memory serves) velocity stacks from a vendor on ebay. They're unfortunately expensive ($25-ish each), but I just closed my eyes and hit "buy it now".  They're coming from the Czech Republic.

Last edited by Stan Galat

I used shorter stacks, but had a problem with the intake air reversion and the jet doctors. The reversion caused the transition to lean out. The car fell on its face until the mains came in, I tried to jet around it but I could never get the mixture rich enough. Idle and WOT on mains was fine. That isolated it to the intake air, which was the only possible change that was made. I removed the jet doctors and the SUPER lean transition disappeared. The car ran absolutely fine with shorter V-stacks.

It's possible that shortening the jet doctors would have worked, but I didn't feel the juice was worth the squeeze. I never really had a clogged idle jet problem like some do.

Apparently the combo of my heads/cam/rocker/intakes causes a LOT of reversion. Right around the torque peak the engine makes a weird intake noise. I don't really know how to describe it, but those who've heard it know what I'm talking about. It's a weird resonance kind of fluttering sound. One guy thought it was pinging, which it absolutely never was or the pistons would have holes in them...probably something to do with 0.575" of lift I'm guessing.

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