Carb issue

quickstang1983

quickstang1983

Club Member
I am having trouble with my carb. Its a proform 750 (mechanical secondaries). Last year when I had the mechanical fuel pump on it I had to jet it up quite a bit so it wouldn't run lean. It ended up OK I guess. It cruised fine. Now this year I put an electric fuel pump on it and it was extremely rich. So, I jetted it down to take care of that. Next, I went for a drive down the road and noticed it was hesitating quite badly under part throttle and just cruising speeds. I thought it might still be a tad rich so I jetted it down again just a little bit and it still has a bad hesitation. If I footbrake the car slowly in gear, when the rpms reach about 1800-2000 it starts to sputter like its missing. It runs great when making a pass and at an idle. The jetting is where it needs to be because I made a hard pass and checked the plugs to make sure and they looked spot on. They seem to be burning clean but the damn carb still has a hesitation when just cruising. It seems fine when I accelerate slowly but if I try to keep a steady speed around 2000rpm it starts to hesitate pretty bad. I played with the timing also and it didn't help any so I am stumped.

Anyone who has some advice or could point me in the right direction would be GREATLY appreciated!!! Thanks, Jake
 
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1BADAIR said:
the cruising problem sounds like a lean miss
Click to expand...

I know its not that because I've jetted up and down many times already and found the current jetting to be just about perfect. It idles nice without being rich and after a hard pass the plugs look nice and tanned. Its only under part throttle between about 1600-2000 rpm when it starts to hesitate or miss. I can bring the throttle up slowly while footbraking and as soon as it hits about the aforementioned 1600ish-2000 rpm it does it. It doesn't do it in park though.:gr_confus
 
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you can get the idle and wot correct but the primary jets can still be incorrect.
at what point do you have timing advance come in?
 
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