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Low Compression Engine

mrsnicks

Well-Known Member
Local time
12:15 PM
Joined
Feb 19, 2013
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Location
cameron, nc
Digging into the 360 engine that came with my project.

Tested the driver's side bank of cylinders, compression was around 30-40 each cylinder which is about 100 too low to run.

I'll test the passenger side tomorrow.

Want to take bets on what the culprit is. You have to get your guesses in before I tear into it and do anymore research.

What I know.

1971 360 engine. Sitting for an undetermined amount of time outside. Long enough that ALL the rubber hoses are brittle and breaking under the slightest movement. Spark plug wires were brittle and falling apart too.

What do we think the cause is for low compression across ALL driver's side cylinders.
 
Stuck rings....leaking valves? Did you squirt some oil into the cylinder to see if it would make any difference?
 
You have to have the carberator plates open for a compression test.

Valves are not opening due to lifters not being pumped up. Closed valves won't create compression.

Make sure your valves are moving. Could have a jumped timing chain.

That's just a start.
 
With compression that low on an entire side, I'd have to guess timing chain has jumped a tooth. My 2nd guess it that the rings are ULTRA bad....but that's a distant second in my opinion. The oil in the spark plug holes vs. a jump in compression is a good idea to check them as cranky said.
 
gummed up valve guides holding the valves open
if so check for bent valves/ pushrods
 
it might fix its self but eventually you will probably have to tear her down. tuff call.
if it was mine I would take it apart to be sent out for honing and some new rings , and a head job
a low budget build
 
Ok. I ALMOST got it running tonight. Had it spitting and sputtering and then the starter locked up. I pulled the cap, set top dead center, and set the firing order from there. From the position it was in when I got it, looks like it jumped timing. Rotor was pointing to the next spark plug wire on the cap compared to when I set it.
 
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