Posted By: Pat_Whalen
Off-idle/cruise stumble - carb tuning issue? - 04/19/11 04:56 PM
Trying to get some of the final bugs hashed out of my build.
Truck starts and idles fine. AFR meter says high 13s, low 14s at idle.
Engine will rev quickly, sharply, and without issue in park.
Once in drive, trying to quickly slap the gas peddle will result in a bog, sometimes a backfire, but the truck "noses over" and won't go anywhere. If I slowly creep into it, once I'm at about 1200RPM, the engine seems to be running OK.
As I'm cruising, if I try and mash it and kickdown, it feels like there is very little power and again, the truck will nose over and not move. Acceleration must be done slowly.
I'll preface all of this by saying I originally had EFI (TBI) on this engine and there were smaller issues surrounding my decision to just go back to a carb. I replaced the the tbi with the carb that was on before it. This, to me, rules out ignition and transmission issues. Initial timing is @ 14* and this is the same distributor that was originally installed with the same carburetor the first time and never had any of these issues.
The ONLY factor that has changed is that I've gone from the stock mechanical fuel pump to an return-style electric setup. I'm still using the fuel pressure gauge on my regulator that is 0-60PSI. Is there a chance that when I try and get it down to 5.5 psi (the gauge reads as 5.5psi) that I'm actually lower?
Thanks for any help.
Truck starts and idles fine. AFR meter says high 13s, low 14s at idle.
Engine will rev quickly, sharply, and without issue in park.
Once in drive, trying to quickly slap the gas peddle will result in a bog, sometimes a backfire, but the truck "noses over" and won't go anywhere. If I slowly creep into it, once I'm at about 1200RPM, the engine seems to be running OK.
As I'm cruising, if I try and mash it and kickdown, it feels like there is very little power and again, the truck will nose over and not move. Acceleration must be done slowly.
I'll preface all of this by saying I originally had EFI (TBI) on this engine and there were smaller issues surrounding my decision to just go back to a carb. I replaced the the tbi with the carb that was on before it. This, to me, rules out ignition and transmission issues. Initial timing is @ 14* and this is the same distributor that was originally installed with the same carburetor the first time and never had any of these issues.
The ONLY factor that has changed is that I've gone from the stock mechanical fuel pump to an return-style electric setup. I'm still using the fuel pressure gauge on my regulator that is 0-60PSI. Is there a chance that when I try and get it down to 5.5 psi (the gauge reads as 5.5psi) that I'm actually lower?
Thanks for any help.
