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Chevy crate engine 350/330 HO

I have a miss and backfire above 2500 rpm. I have replaced everything in HEI and put new spark plug leads as well as new plugs. When I checked timing it read 12' BTDC. Is that too high? Should it be set lower to like 4-7 BTDC?
 
Thanks Grant I start on the carb next. Meanwhile I did replace my fuel filter and the elec fuel pump sounds?? OK This engine has run perfect for four years and 285 hours so I guess I'm due.
 
Beau, bring it in and I would be glad to take a look at it for you. I would call Stan if you are worried about the timing. Only person I have ever had a problem with on one of those engines fooled with the timing and blew the motor.

JMO,
Faron
409-920-0716
 
Mechanical advance seizied? Check initial and watch timing up to max timing at what RPM. Did the miss come on gradual or all of a sudden? Popping back through the carb? to lean, bad cam lobe, broken valve spring, timing issues!
 
Hi Faron, I would love to take this boat over to your dads but they are very very busy. I think I can take the carb off and have it overhauled. I may,however, call over to your dads and ask for timing advise or look at a new stand and a 502.
 
Your timing is ok, that's not the prob/

First thing I would do is take the valve covers off and rotate the engine over slowly. Watch all the rockers and look for one (or more) that isn't moving as much as the others. That could mean a wiped cam lobe. A wiped exhaust lobe will trap the spent mixture in the cylinder and it can't get out until the intake valve opens.....POP POP!

It could also be a stud pulling out or a rocker that is way too loose.

This is an easy check and if that looks ok then you can go from there.
 
Beau, I'm runnin the same motor on my rig, never had any problems with the timming,I would check all the things people have told you to check plus one other thing,I would check to see if you have any water in your gas.I had this problem 1 other time and thats what turned out to be the problem.
 
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