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Ok it had bad headgasket so replaced an now got good compression but still rev pretty slow an when load put on it back fire through intake some times so what could be bad intake valves or something ?
Any info be helpful

 
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Your distributor wires could be in the wrong order!

 
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or the timming belt could be off a tooth or 2

 
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that sounds like the problem,
use a timing light and check timing as well

 
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That would explain the power loss, but I don't believe that creates backfiring through the intake.

 
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it will because the compressed charge in the cylinder has not been ignited, so when the valves open for the next stroke the previous compressed air has to escape somewhere, definatly a timing issue, the timing light will be useless if you are a tooth or two off, pull the valve cover gasket, and check for sure the timing mark on the back of the cam gear is correct

 
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Dead on, thanks just save me alot of typing.
Jay
Fabricated Performance

 
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The valves are all closed for the compression and the power stroke. So how would the teeth being off a tooth or to affect it between those two strokes? If the ignition is still working properly then it will still ignite. The only way it would get gas in the intake is if the cam was retarded and then it would still not have an ignition source. The only real way it could ignite is if it was advanced alot and the valves where opening at the end of the power stroke, because the fire would still be burning but that would be through the exaust valves.

Basically. For what you are explaining to happen, I think the timing would have to be really off and the thing would not run and he would probably have some bent valves.

Please explain bacause I still don't understand when you believe this is occuring. I am not trying to argue, it just does not make sense to me.

If the ignition was off then it would be firing at a completely wrong stroke which could allow for ignited gasses to go back inside of the intake during the intake stroke when the intake valves are open.