You have to be at Top Dead Center on the Compression Stroke. This
means the Intake & Exhaust valves should be fully closed.
Car engines are 4 stroke, except for wankle/rotary engines. The 4
Intake- Intake valve open, piston going down to BDC.
Compression- Both valves closed, piston coming back to TDC.
Power - Both valves closed, mixture ignited, piston going back to BDC
Exhaust- Exhaust valve opening, piston coming back to TDC.
If you have a valve hung open, you will have no compression.. A good
way to make sure your valves are closing is to remove the valve cover,
and watch them. While rotation the motor over by hand. If a valve does not
move or return to full sealing height during all 4 strokes you have a
Thanks I took every thing apart and found all 6 exhaust valves and the
pushrods bent. I didn't realize that the 3.8 engine was an interference
engine. I thought when my timing chain lost all the teeth on the cam
sprocket, I just had to change the timing set. Oh well live and learn
Ouch. Sorry to hear about the bad luck. My advice is to get a set of
used heads. Have them pressure tested, and decked. Around here salvage
yards of good stature will do that included in the purchase price.
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