Poor 351W compression
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Joined: May 2005
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Poor 351W compression
I bought a 1985 F150 / 351W / C6 / XCab for $300, beacuse the owner said the tranny was bad. The engine would start and run, but seemed to run oddly. It is a Factory crate engine, has approx. 20K miles on it. I rebuilt the C6 putting a shift kit and a NEW converter in upon installation. Started the engine and it did the same thing: died immediately upon putting the truck in gear, and I cannot rev it up and keep it running. Thinking logically (finally!!) I did a compression test on the engine...lo and behold, cyl's 1-4 have 25 psi dry and 50 psi if I oil them. Cyl's 5 & 6 have virtualy 0 psi compression (the valves are opening and closing, after doing a visual check), and cyl's 7 & 8 are running at 125 psi...before I open the engine up, does anyone have any ideas? The previous owner said he was driving and all of a sudden the engine bogged down very bad and he barely was abole to nurse it up a hill to his buddy's house to catch his ride to work...he was told that he might have a clogged catalytic converter, so he chopped out a foot long section of exhaust pipe but that was not the problem...now that I have the truck, I have learned about the compression. HELP!!!!!!!!
Junior User
Joined: May 2004
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Sounds like a rebuild & inspection of the motor is indeed needed. Sounds like the crate motor went bad or neglect or you kinda got the shaft but that may need to be determined. Have you looked at the oil for viscosity/ wear debree??? If you visual checked for valve movement did you see buildup of oil crud in the valve covers???
1 more thing, does the oil pressure gague work??
1 more thing, does the oil pressure gague work??
Last edited by luvinfords; May 15, 2005 at 09:40 PM.
