quadrajet question
Thread Starter
Intermediate
Joined: Jun 2010
Posts: 29
Likes: 2
From: Cairns Qld Australia
quadrajet question
My 1975 L82 has quadrajet #7045203 TS
engine is 355 with AFR 190 68cc heads &
Lunati 60103 cam.
It seems to starve for fuel at about 5000 rpm.
Should I change carb.
Thank You
engine is 355 with AFR 190 68cc heads &
Lunati 60103 cam.
It seems to starve for fuel at about 5000 rpm.
Should I change carb.
Thank You
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,170
From: Hermosa
q-jet is more than adequate. Check for reasons for fuel starvation. Low float level, low flow from the pump, dirty sock filter in the tank etc.
Tech Contributor
Joined: Aug 1999
Posts: 14,370
Likes: 6,364
From: At my Bar drinking and wrenching in Lafayette Colorado
Your Q-Jet is a 750 cfm carb, and will easily support a 355 engine through 7000 rpm. You have a fuel supply problem or a carb setup problem. You can also have timing/ignition system issues that can cause the symptoms of fuel starvation.
Typical issues that will cause the symptom you describe:
The stock needle/seat as supplied in good quality rebuild kits will support engines through 500 hp as long as fuel pressure is in the 6-7 psi range. The "improved design" aftermarket press-in seats with the "popper valve" design is crap and will cause fuel starvation problems.
Lars
Typical issues that will cause the symptom you describe:
- Inadequate total timing
- Improper timing advance curve
- Plugged fuel tank pickup sock
- Kinked fuel line (at tank or at frame rail)
- Plugged fuel filter
- Inadequate fuel pressure
- Low float
- Incorrect primary jets
- Jammed or damaged power piston
- Incorrect secondary rods
- Incorrect secondary airvalve spring windup
- Ruptured choke pulloff
- Incorrectly adjusted choke - secondary lockout not retracting
- Improper throttle cable travel/adjustment
- Incorrectly adjusted/damaged secondary linkage
The stock needle/seat as supplied in good quality rebuild kits will support engines through 500 hp as long as fuel pressure is in the 6-7 psi range. The "improved design" aftermarket press-in seats with the "popper valve" design is crap and will cause fuel starvation problems.
Lars
Last edited by lars; Jan 2, 2015 at 11:35 PM.
Tech Contributor
Joined: Aug 1999
Posts: 14,370
Likes: 6,364
From: At my Bar drinking and wrenching in Lafayette Colorado
Radial shaft play at the bottom of the distributor is indicative of lower bushing failure. The play itself will not cause the problem you describe, but in order for the lower bushing to fail on an HEI, something had to go through the bushing to cause the failure. I'd be concerned about what it is that went through the bushing to cause the failure - where did the metal debris come from that trashed the bushing...? You may have something failing other than the distributor, which could be the cause of your issue. Cut your oil filter open and see if you have metal in the filter: If you have a cam lobe going bad, it will cause the problem you have, and it will shoot metal into your distributor shaft and trash the bushing...
Lars
Lars
Last edited by lars; Jan 4, 2015 at 12:18 PM.
