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Optimum compression numbers for 429
I have been battling a hot no restart condition for weeks. I been over everything and have found that compression is my enemy in this case.
I checked the compression on the engine cold had numbers ranging from 220 to 180psig with one way down at 155. I know the 155 is bad with the rest of the numbers where they are, but one thing at a time. What would one reasonably expect to find in a PO rebuilt job with out any info or parts list from the build to go on? I tried to recheck compression on the motor after a heat soak and something really wierd happened. With all the plugs out and the ignition off I used my push button remote to turn the motor over. With my compression tester in the #1 hole I hit the button. The gauge jumped out of my hand and I thought for a moment the engine fired? I double checked! No cap on dizzy, all plugs out, key off. Picked up my compression tester and the needle was pegged. On my gauge that means well over 300 psig. Hit the pressure release and rechecked it and read 265PSIG. After doing 1-4 I realized that the gauge was not returning to 0. It was now at 35psig instead of 0. So just for the sake of arguement lets say all the cyls gained roughly 10-15 psig after heat soak. That puts me now at 235 on the high end and 170 on the one low cyl. That seams rediculous to me. What are your thoughts. I aint no guru! I am literally at my wits end on this deal. Todd |
Originally Posted by todd jo
(Post 9425033)
I have been battling a hot no restart condition for weeks. I been over everything and have found that compression is my enemy in this case.
I checked the compression on the engine cold had numbers ranging from 220 to 180psig with one way down at 155. I know the 155 is bad with the rest of the numbers where they are, but one thing at a time. What would one reasonably expect to find in a PO rebuilt job with out any info or parts list from the build to go on? I tried to recheck compression on the motor after a heat soak and something really wierd happened. With all the plugs out and the ignition off I used my push button remote to turn the motor over. With my compression tester in the #1 hole I hit the button. The gauge jumped out of my hand and I thought for a moment the engine fired? I double checked! No cap on dizzy, all plugs out, key off. Picked up my compression tester and the needle was pegged. On my gauge that means well over 300 psig. Hit the pressure release and rechecked it and read 265PSIG. After doing 1-4 I realized that the gauge was not returning to 0. It was now at 35psig instead of 0. So just for the sake of arguement lets say all the cyls gained roughly 10-15 psig after heat soak. That puts me now at 235 on the high end and 170 on the one low cyl. That seams rediculous to me. What are your thoughts. I aint no guru! I am literally at my wits end on this deal. Todd However the problem you experienced after the heat soak is that there is water or oil or both in the cylinder, because that is the only way you could get that big of a jump. Oh and you destroyed your compression gauge. I would pull the heads to check the gaskets and when I reassembled the motor I would use the thickest head gaskets I could find as you need to get down to about 9.0 to 9.5 to 1 compression. |
Would I not have some other signs of a bad head gasket?
It seems wierd that it only happened the one time, and on one cylinder? Is there another way to check for a bad head gasket? I dont doubt what you are suggesting, because it is sound in theory. |
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