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Hey all. My brother has a 69 cougar with a 347 stroker. Car is running msd digital 6 box, and fast ez efi. His having a problem with backfiring out the exhaust while at a cruise. He called fast and they are kind of stumped. They sent out a new computer but that did nothing. Timing is locked out at 28 degrees. Can't find any vacuum or exhaust leaks. Any ideas?
 

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Have you checked to make sure the plug wires are in correct order? That will be a sure back fire problem, just a thought and I think sometimes water in the gas will create a backfire.
 

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Unburned fuel in the exhaust. Run a compression check and check for a misfire.
 

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compression test was good across the board. Don't remember numbers right now. Yes timing is locked at 28 degrees. No vacuum advance or mach. Double checked spark plug wires, all correct order. As far as how bad the backfire is, its a pretty loud and consistant pop over 3000 r.p.m. Another thing is the car is way down on power.
 

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compression test was good across the board. Don't remember numbers right now. Yes timing is locked at 28 degrees. No vacuum advance or mach. Double checked spark plug wires, all correct order. As far as how bad the backfire is, its a pretty loud and consistant pop over 3000 r.p.m. Another thing is the car is way down on power.
turn the timing up to 34* for a start . bor got a start retard ..?... use it i
 
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