carberator sputter
Thread Starter
Burning Brakes
Joined: Feb 2005
Posts: 1,235
Likes: 0
From: Mesa AZ
carberator sputter
i have a 75 with an L48 350 with an original style q-jet. i was adjusting the carb the other day and got it running good, but at about 2,000 rpm it sputters like its getting no gas. but at idle it runs fine and above 2,000 it runs fine. i tried adjusting the air mixture screws and it got better but now its sputtering again.
the way i adjusted the air screws was : i tightend them until the idle dropped and then backed them off untill it returned to a good idle. i then adjusted the idle to about 1000 in park.
the timing is at 6* btc and the carb has 6 months of driving since it was rebuilt.
it didn't start acting up untill i fixed the vacuum adv. which was stuck. i hooked the vac adv. to a vacuum line that only gets vacuum when the engine is revved up( no vacuum at idle).
has anyone had this problem?
the way i adjusted the air screws was : i tightend them until the idle dropped and then backed them off untill it returned to a good idle. i then adjusted the idle to about 1000 in park.
the timing is at 6* btc and the carb has 6 months of driving since it was rebuilt.
it didn't start acting up untill i fixed the vacuum adv. which was stuck. i hooked the vac adv. to a vacuum line that only gets vacuum when the engine is revved up( no vacuum at idle).
has anyone had this problem?
Tech Contributor
Joined: Aug 1999
Posts: 14,370
Likes: 6,364
From: At my Bar drinking and wrenching in Lafayette Colorado
Before playing with the carb, you need to fix your timing. 6 degrees initial is way short. Set your timing to 36 total. This will likely get your inital timing into the 16-18 degree range. Hook up your vacuum advance to a direct manifold vacuum source (the 1975 HEI cars used direct manifold vacuum to the distributor - not ported vacuum - ported vacuum was used to operate the EGR only). Wth this done, you'll be running timing at idle in the 30-degree range. See if that fixes your flat spot.
