have a 750 VS carb on my 355 ( 375 HP).


The problem i'm having is in 1st gear only at roughly 4-4500 RPM the car slightly noses over then picks back up and runs strong throughout the rest of the RPM band and the rest of all the gears. I have good fuel pressure throughout the run and have tried several springs. @ days ago i went from the purple to the shortest yellow and this seemed to fix it. Then last night i took the car out again and had the same problem.


Has anyone had this problem and what was the fix ?

Mike

Whats the jetting front and rear?

I'd say jetting or....

...isn't there a somewhat rare situation where the power valve can flutter open and closed on the top end? Seems like I read about it in one of my Holley manuals or something. Have you tried putting a vacuum gauge on it to see what it reads when this "nose-over" occurs?

What fuel pump and what size fuel lines are you using? Then again you say you have good fuel pressure. Hmmmm. What pressure is it running?

You need to disconnect the secondary side and test the car again to determine if this problem is related to the primaries or secondaries. I'm sure it is a lean spot, make sure your rear float level is set right, a low fuel level might delay the fuel flow through the secondary boosters. Your secondary spring may also be to weak.

I ran the car on the dyno and the A/F was 14-1 @ 2K, it went up just a touch at 3K, at 6K it was 12-1. i went from 70-72 primaries, 76 rear shortest yellow spring. I ran flawlessly on the dyno and at the track. Time posted in the thread above.

After watching the video i noticed it puts out some black smoke right as i take off, i have a blue cam in the #2 pos. with a #37 tube type squirter, i'll try a #35 and see what that does. I had a stealth intake and bigger cam and that was the only way i could get the off throttle stumble to go away.

thanks

OH, I didn't know you could disable the secondaries on an VS carb ? How do you do that ?