My buddy has been having trouble with a popping sound coming from his 5.7 merc. Did a compression test today and the #6 cylinder had no reading of compression. Motor seems to run fine with exception of a popping sound from time to time and top end is off a few hundred rpm.

What should we be looking at as the cause of this problem??? What should we dig into first??

Thanks for your help!!!

Intake valve not opening, possibly caused by a flat cam lobe or??????

Or a BIG hole in the #6 piston.

Time to pull the head off and do some inspecting, also could be possible to have bad intake valve...

I'd check the valvetrain forst starting with the pushrod and rocker assembaly for that cylinder, sounds like a bent pushrod but they are often cuased by something else like a bent or frozen valve or a broken lifter. If you do find a bent pushrod you have to find out why.

Popping Though Intake Or Exaust???? Could Be Bad Or Burnt Valve, Bad Guild, Bent Stem, Bad Seat, Ect......... Need More Info To Narrow It Down.....

This is what you are looking for...

Stuck valve would be my first guess.

dave that wont give popping just a hell of alot of blow by

Eliminate the guess work & do a leak down test.

Thanks everyone!!

We'll start on the top end with the heads/valves and hopefully find the problem there...... at least it's the end of the season if we have to go all the way in!!!!

Good day everyone!!!!