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Pontiac Interference Engine


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atwitsend
Anonymous Poster
opie@centurytel.net

Sep 10, 2008, 6:36 AM

Post #1 of 2 (2937 views)
Pontiac Interference Engine Sign In

1992 Pontiac Grand Am Quad OHC TERRIBLE engine noise.

Car died in traffic. It will start and run for about 2 seconds. Middle two plugs almost had electrodes burned off. Compression reads 62lbs. on outside cylinders and 58lbs. on inside two cylinders. Proboscope analysis of piston top does not show any visible damage from valves striking pistons. Could problem be broken timing chain tensioner without resulting damage to piston from valves? With compression low but consistent I suspect that timing is off and compression reading on the wrong stroke. How can I further determine if valves are bent from striking pistons (without pulling head)?


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Sep 10, 2008, 5:22 PM

Post #2 of 2 (2922 views)
Re: Pontiac Interference Engine Sign In

It may not have interferred yet but valve timing could be off by a problem with the timing chain(or is this a belt?) - tensioner or something allowing it to be off. Compression being even is a good sign so far. It would run like crap with just a couple "valve" degrees off and as said may not have crashed pistons to valves yet so check this out asap,

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