[Mike S]

I have been having a problem last year. It would be rich for first gear (10.8). Then slowly come up to 12.8-13.2 by the middle of second gear and stay there for the rest of the run. Same with or with out the PV. If I lean the jets it has better 60's but looses mph and runs leaner top end.
I was thinking. Could I be getting more air at speed leaning the carb? Even with a cowl scoop? Anyway to fix the problem?

[grandville455]

Mike Look into this....

http://racingfuelsystems.myfunforum.....php?f=25&t=15

[charlie66]

Maybe try a smaller pumpshot - squirter?

[AG]

The pressure generated going 130 mph at 60°F is only 0.3 psi, very little supercharging effect.

[J.C.you]

Originally Posted by grandville455

Mike Look into this....

http://racingfuelsystems.myfunforum.....php?f=25&t=15

after skimming thru the link, I did not see any back to back tests listed that improve a/f ratio thru the engine cycle? One thing noticed, bars going across the top of the carb that would disrupt air flow into the carb would be bad.

[grandville455]

Originally Posted by J.C.you

after skimming thru the link, I did not see any back to back tests listed that improve a/f ratio thru the engine cycle? One thing noticed, bars going across the top of the carb that would disrupt air flow into the carb would be bad.

...Maybe not that particular thread , but on the old MSV forum there was guys talking about a change in A/F after adding the flute

Jc, This is a response from jmark(mark whitner) on that forum about the Flutes

It is used when turbulence causes pressure fluctuations at the vents. The bowl vents provide atmospheric pressure that pushes fuel in through the carb. When there is turbulence at the vents from a poor scoop design it will disrupt the fuel curve making it erratic and most of the time you see the fuel curve go lean. Adding vent tubes like shown will fix it if there is a problem, and have no impact if there isn't.

[J.C.you]

I could see doing the old sparkplug boot trick with the inlets pointed toward the bowls helping..... There is a reason vents are cut on a *45 angle away from the center of the carb.

[cgeise]

Id try jetting for good early numbers then air bleeds to get fuel curve correct - MAKE SURE THE FUEL SYSTEM IS ADDIQUATE and your not leaning down due to fuel volume down track.

[p4msi1]

Find a chassis dyno and run it there where the car a just stationary. It will eliminate the scoop turbulance factor. If it does the same thing just do what Curt posted. I believe it will at least point you in the right direction in finding the solution.

Steve

[mjm421]

Originally Posted by charlie66

Maybe try a smaller pumpshot - squirter?

Or cam. 30 or 50 cc pump?

[charlie66]

Originally Posted by mjm421

Or cam. 30 or 50 cc pump?

When I think about it, it seems almost like a residual thing. Maybe its burning off excess fuel from the mechanical pump area. I mean how long is anyone in first. I know as soon as I launch I hit second or I go slower. If you don't like 13.00 + at the top of 3rd then just add a couple of sizes in the back And drop the front.. Anyway, Just a quick thought..

Good luck. you will figure it out....

[screamingchief]

Originally Posted by p4msi1

Find a chassis dyno and run it there where the car a just stationary. It will eliminate the scoop turbulance factor. If it does the same thing just do what Curt posted. I believe it will at least point you in the right direction in finding the solution.

Steve

I like this ^^^^ line of reasoning.

To add to that,try it w/the hood on -and- w/the hood off as well.

Could be a clearance issue as well,have heard of some lightweight glass hoods getting "sucked down" and reducing carb airhorn 2 hood clearance during a run.

FWIW

Bret P.