1979 Corvette Backfiring Problem
Thread Starter
Heel & Toe
Joined: Jan 2007
Posts: 23
Likes: 0
From: Highland Indiana
1979 Corvette Backfiring Problem
Hello,
I just recently purchased a 1979 with a rebuilt quadrajet, edlebrock manifolds and headers. The car backfires through the exhaust when decelerating. A local mechanic told me it was an emissions control problem and could possibly look atit in May!!! The previous owner claimed it was a hot air choke problem. Please help me if you can.
Pictures:
http://www.torrenga.com/images/79vette/IMAGE002.jpg
http://www.torrenga.com/images/79vette/IMAGE003.jpg
http://www.torrenga.com/images/79vette/IMAGE004.jpg
http://www.torrenga.com/images/79vette/IMAGE005.jpg
I just recently purchased a 1979 with a rebuilt quadrajet, edlebrock manifolds and headers. The car backfires through the exhaust when decelerating. A local mechanic told me it was an emissions control problem and could possibly look atit in May!!! The previous owner claimed it was a hot air choke problem. Please help me if you can.
Pictures:
http://www.torrenga.com/images/79vette/IMAGE002.jpg
http://www.torrenga.com/images/79vette/IMAGE003.jpg
http://www.torrenga.com/images/79vette/IMAGE004.jpg
http://www.torrenga.com/images/79vette/IMAGE005.jpg
Safety Car
Joined: Dec 2004
Posts: 4,876
Likes: 1
From: Jersey Shore Exit 98
It may not be a true backfire your hearing. W/headers and true dual exhaust you maybe hearing just back pressure. Is it a loud bang or POP then another Bang POP sound or a low multi popping sound. You can try playing w/the timing could be electrical. Ask someone in the area who owns a vette before you give a garage money for nothing.
Race Director
Joined: Mar 2006
Posts: 14,112
Likes: 28
From: Florida
It is usually a sign of a lean condition. Those year carbs were lean anyway having been rebuilt, who knows.
Make sure your timing etc is right and your exhaust gaskets are tight.
Post your carb model # to see if it's close with jetting. A manifold/headers combo will require a rejet for sure, even if everthing else was right before the change.
Make sure your timing etc is right and your exhaust gaskets are tight.
Post your carb model # to see if it's close with jetting. A manifold/headers combo will require a rejet for sure, even if everthing else was right before the change.
Melting Slicks
Joined: Sep 2004
Posts: 3,223
Likes: 666
From: Northeast
According to Haynes troubleshooting-Engine backfires:
1. Emissions system not functioning properly
2. Ignition timing incorrect
3. Faulty secondary ignition system (cracked spark plug insulator, faulty plug wires, distributor cap and or rotor)
4.Carburetor in need of adjustment
5. Vacuum leak
6. Valve clearances incorrectly set or valves sticking in guides
7. Crossed plug wire
Sounds like everything discussed so far and more
1. Emissions system not functioning properly
2. Ignition timing incorrect
3. Faulty secondary ignition system (cracked spark plug insulator, faulty plug wires, distributor cap and or rotor)
4.Carburetor in need of adjustment
5. Vacuum leak
6. Valve clearances incorrectly set or valves sticking in guides
7. Crossed plug wire
Sounds like everything discussed so far and more
Le Mans Master
Joined: Jan 2006
Posts: 9,192
Likes: 27
From: Boca Raton Florida
Nothing like narrowing it down some, LOL.
I would approach it by making sure as many things are as right as I could. Barryk has a great timing paper on a sticky at the top of this forum. Lars the carb guru has a great q-jet tuning paper for the asking. Your stuff is rebuilt according to what you were told by the PO or someone. That has nothing to do with it being right. Read the stuff available in here and see what applies to your situation.
I would approach it by making sure as many things are as right as I could. Barryk has a great timing paper on a sticky at the top of this forum. Lars the carb guru has a great q-jet tuning paper for the asking. Your stuff is rebuilt according to what you were told by the PO or someone. That has nothing to do with it being right. Read the stuff available in here and see what applies to your situation.
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