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Old January 3rd, 2007, 01:42 PM   #1
Mijeeper CJ 7
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Default 390 Issues

I've got a 76' F150 with a 390 4 barr.carb 4 speed manual trans. It had a exhaust leak that I fixed and now it's back firing through the carb. It only does it under power. I can rev it in neutral & no back fire. I replaced the vaccume lines and put a new carb gasket on it. Checked the timing and it seems to be fine. Put new mufflers on it. What am I missing here?
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Old January 4th, 2007, 12:24 AM   #2
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Do a compresson test on it . FE blocks did not have hardened valves . No lead fuel takes out the exhaust valves .

Popping thru the carb would indicate an intake valve problem rather then exhaust valve though .

Intake valve to tight ? they been adjusted lately ?

Id start with the compression test . Have a cyl down then check adjustment .
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Old January 4th, 2007, 07:30 PM   #3
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Thanks G-Man
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