Help, What's causing backfiring?
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Instructor
Joined: Jan 2002
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From: Knoxville TN
Help, What's causing backfiring?
Project car (1970 conv, 350, auto, w/AC, Qjet) is acting up. I've been busy, so it has sat for a month.
New points, timing set at about 6 BTDC. Dwell is about 28.
Car starts fine, but won't go pass 2000 prm without popping or backfiring. I pull the vacuum from distributer it's fine. Let it warmup, it gets better.
Is it the points? Timing? Vacuum? Carb?
(and I have a small exhaust Hooker header leak and Bad pipes and mufflers)? After Corvette Expo, going back to stock manifolds and stock exhaust.
Any Advice is welcomed.
Thanks
:confused: :confused: :confused:
[Modified by 78whtshark, 1:59 PM 10/11/2003]
New points, timing set at about 6 BTDC. Dwell is about 28.
Car starts fine, but won't go pass 2000 prm without popping or backfiring. I pull the vacuum from distributer it's fine. Let it warmup, it gets better.
Is it the points? Timing? Vacuum? Carb?
(and I have a small exhaust Hooker header leak and Bad pipes and mufflers)? After Corvette Expo, going back to stock manifolds and stock exhaust.
Any Advice is welcomed.
Thanks
:confused: :confused: :confused:
[Modified by 78whtshark, 1:59 PM 10/11/2003]
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Re: Help, What's causing backfiring? (78whtshark)
What is your timing at 2000 rpm?
I am thinking you vacuum advance is hooked to manifold instead of ported, possibly.
I too believe I have an exhaust leak and a popping problem under heavy accelaration. Maybe that is both of our problems.
I am thinking you vacuum advance is hooked to manifold instead of ported, possibly.
I too believe I have an exhaust leak and a popping problem under heavy accelaration. Maybe that is both of our problems.
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Re: Help, What's causing backfiring? (78whtshark)
Check your fuel pump or fuel filter, if you have a Q-jet you probably have the little brass filter right in the inlet of the carb. They can plug very quickley. The backfiring can be a sign of an extreme lean condition caused by fuel starvation. The fact that it runs fine up until 2000 rpm under load sort of hint at this.
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From: Knoxville TN
Re: Help, What's causing backfiring? (Smokehouse69)
Smokehouse69, LAvetteman,
Thanks,
I'll change out that brass filter, who knows what was in the lines (this car sat for 15 yrs) and then the fuel pump (probably needs one).
Timing is fine if distributor vacuum is pulled off. As for location, I have its vacuum coming off the side of the carb.
As for manifold/header leaks, soon I will take care of them with a new exhaust system from engine to the rear of the car.
It's a project car so slowly, I'll get it roadable again.
Thanks,
I'll change out that brass filter, who knows what was in the lines (this car sat for 15 yrs) and then the fuel pump (probably needs one).
Timing is fine if distributor vacuum is pulled off. As for location, I have its vacuum coming off the side of the carb.
As for manifold/header leaks, soon I will take care of them with a new exhaust system from engine to the rear of the car.
It's a project car so slowly, I'll get it roadable again.
