new engine backfires...I'm lost
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Joined: May 2002
Posts: 65
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From: York pa
new engine backfires...I'm lost
Happy Thanksgiving. I have a 78 that I've had for 15 years. I wanted to replace the engine so I bought a GM 'target' engine. I autocross and I wanted to stay in my class. I had my regular garage install it. Now to the problem, after about 15 minutes of driving it starts to backfire through the carburetor and some through the exhaust. The engine came complete except for the intake, distributor and water pump and pulleys. I used the original intake and carb, got a new distributor. This is a new engine, not remanufactured. I appreciate any help anyone can give me.
Thanks
John
Thanks
John
Drifting
Joined: Mar 2001
Posts: 1,514
Likes: 1
Re: new engine backfires...I'm lost (SanDiegoPaul)
I agree with the other posts. The distributor more then likely, possibly the module is going bad as it heats up. Any other scenario that would cause that, misadjusted valves or carb would be evident right at startup I believe.
Scott
Scott
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Race Director
Joined: Feb 1999
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From: In Dreams There Is Truth Ohio
Re: new engine backfires...I'm lost (John2)
That's the problem, muffler bearings....and while at it, recheck timing, as others have posted....backfire caused be retarded timing....you could be off a tooth, or two, recheck the rotor to the #1 firing order at TDC.
Burning Brakes
Joined: Mar 2001
Posts: 1,211
Likes: 5
From: Nashville TN
Re: new engine backfires...I'm lost (GDaina)
How about the hemi-posi door handle gaskets ? Are they torqued to spec ?
A change to synthetic blinker fluid can also cause this..
A lean condition may also be occuring, 15 minutes would give with the choke being fully open. Make sure the the carb is torqued down, and that there are no vacuum leaks.
A change to synthetic blinker fluid can also cause this..
A lean condition may also be occuring, 15 minutes would give with the choke being fully open. Make sure the the carb is torqued down, and that there are no vacuum leaks.
Race Director
Joined: Apr 2000
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
Re: new engine backfires...I'm lost (dman535)
Oscillating flyback rectifier could need an adjustment. Also check all the plug wires and connectiions to distributor and reset the timing.
Le Mans Master
Joined: Jan 2000
Posts: 8,721
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From: Canada
Re: new engine backfires...I'm lost (MotorHead)
Are you all sure it's not a bad mating with the humphalumpagus and the flying gremlin? Lots of great suggestions and I agree to recheck your timing and advance.
Drifting
Joined: Mar 2001
Posts: 1,514
Likes: 1
Re: new engine backfires...I'm lost (gdh)
Actually there is one other thing not mentioned yet. If you still have the stock manifold and your running EGR and EFE. Both are switched by thermostatic switches located in the thermostat housing. After 15 minutes I would think the coolant is up to a temp to trigger those switches and that is when a vacuum leak could be present in either actuator. Just a thought as I sit here trying to digest what would normally be 4 days worth of food :lol:
