1978 Other GMC Models Bad knock

1978 GMC
80,000 MILES • V8 • 2WD • AUTOMATIC
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78SHORTY
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Yesterday I sprayed the engine with degreaser so I could change the valve cover gaskets. I wasnt able to do it then so I left it untill the next day. When I started it up there was a horrible knock I think was in the top end. I tried starting it twice since then and it still does it. I only let the motor run for about 5-7seconds andshut it down.Could the degreaser ate through the old valve gaskets and it made it way down on to the valves or something?
Sep 28, 2008 at 6:00 PM
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RASMATAZ
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Yesterday I sprayed the engine with degreaser so I could change the valve cover gaskets.

Why are you degreasing it-check the oil level if okay-check oil pressure with a mechanical gauge-if within normal readings -check valve clearances and lifter/camshaft.
Sep 28, 2008 at 7:04 PM