quick backfiring question
Thread Starter
Instructor
Joined: Dec 2008
Posts: 116
Likes: 0
quick backfiring question
this past saturday i just put on new plug wires, distributor cap, and a edelbrock 600 cfm carb. the car revs great with no miss at all. on deceleration there is a poping sound. i have yet to tune the carb it is sitting as it did right out of the box. should that be the first thing i do or is it more likely a timing issue? thanks.
Safety Car
Joined: Oct 2004
Posts: 3,921
Likes: 731
From: Youngstown Ohio
First thing, double check firing order (especially #5 & #7 wires)...if OK, then check timing; possibly slightly retarded, or plug wires might need repositioned 1 hole on cap....if OK, then check plug wires (for good contacts, and not grounded against anything..........when you're satisfied all wires OK, then check carb....begin with float levels and go from there.
This procedure has gotten me out of trouble on several occasions when I thought the trouble was more major.
This procedure has gotten me out of trouble on several occasions when I thought the trouble was more major.
Racer
Joined: Mar 2006
Posts: 366
Likes: 1
From: Houston Texas
If all you did was replace the cap, the timing and distributor orientation should be the same.
A lean condition can cause both carb backfire and exhaust popping. I'd look to the carb adjustments first.
A lean condition can cause both carb backfire and exhaust popping. I'd look to the carb adjustments first.
Pro
Joined: Jun 2005
Posts: 725
Likes: 1
From: FL.
Get a vacuum guage, your engine should hold steady Vacuum at least 15 at 900rpms. If the vacuum readings act strange you may have a open port. or leak somewhere.
Double check the carbs specs. If theres no change, Mark the dist. loosen and move it counter clockwise a tiny bit. Drive it, if its improved move it a tiny more until no popping. If its worse or no better in step one, move the dist Clock wise a little and so forth. if you get no results with the dist. timing. Its the carb. Maybe some debris sticking the float bowl , something like that?
Double check the carbs specs. If theres no change, Mark the dist. loosen and move it counter clockwise a tiny bit. Drive it, if its improved move it a tiny more until no popping. If its worse or no better in step one, move the dist Clock wise a little and so forth. if you get no results with the dist. timing. Its the carb. Maybe some debris sticking the float bowl , something like that?
Last edited by 69vettester; May 9, 2009 at 02:07 PM.
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getting really frustrated here.
Thread Starter
Instructor
Joined: Dec 2008
Posts: 116
Likes: 0
the carb is not even two weeks old yet. the guy before me had a clear inline fuel filter on it. when i went out last night it had gone from clear to a bunch of orangish colored stuff in the filter. i am starting to think it may be a fuel problem.
Drifting
Joined: Apr 2006
Posts: 1,911
Likes: 2
From: gold coast queensland
so its less then 2 weeks old but the guy before you had a filter on it? i dont get it.....he didnt have it very long then? sounds like you have found your problem anyway