Piston Ring Job

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Jan 12, 2010 | 10:05 AM

1977ford250

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Piston Ring Job

Hi, I did a compression test on one of my 300's and it came up low in 3 of the cylinders. i then did a wet compression test and they all came up so i have bad rings. Would it be easier just to pull the motor and do it that way or could i pull the head and the oil pan and do it in the truck? thanks alot, for all you opinions, Mike.

Jan 13, 2010 | 06:50 AM

chrlsful

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From: Lawrence Swamp

...I did a compression test on one of my 300's ...for all you opinions

Hi Mike!
I'm learning that the test needs to B done w/all plugs out B 4 going to each cyl w/your tester.
Imagine U did it that way.
How is the 'wet' test done. Good Luck w/the motor(s).
cf
BTW: if U wanna do rings, just pull the head, turn each piston up from the crank, don't even need to remove the pan. (from a non-mechanic)

Last edited by chrlsful; Jan 13, 2010 at 06:53 AM. Reason: additions

Jan 13, 2010 | 09:40 AM

Brigart

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You can pop in new rings with just the head and pan off. The difficulty is there is usually a ridge built up at the top of the cylinder. Removing that without leaving debris in there is the hardest part.

Not every repair requires an engine overhaul but.... I wouldn't be shocked to see those rod bearing worn out too if the rings are shot.

Good luck

Brigart

Jan 13, 2010 | 10:24 AM

F-250 restorer

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From: Near Los Angeles

If it were me I would want to check the rod and mains before going to all the trouble of doing the rings. What I found would determine whether or not I pulled it and rebuilt the engine.

Good luck.

Jan 13, 2010 | 10:25 AM

chrlsful

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From: Lawrence Swamp

Quote:

Originally Posted by Brigart

You can pop in new rings with just the head and pan off. The difficulty is there is usually a ridge built up at the top of the cylinder. Removing that without leaving debris in there is the hardest part.
Not every repair requires an engine overhaul but.... I wouldn't be shocked to see those rod bearing worn out too if the rings are shot.
Good luck
Brigart

Ahh, thanks for the additions, Brigart.
The old ridge n bearings - how do U chk the bearings. By eye, by wiggle or do U hafta disasemble? If a finger nail test sez 'ridge problems' how do U keep the shavings outta cyl as you are machining? I guess you can't?

Jan 13, 2010 | 02:38 PM

73'360f100

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From: Newnan,Ga

you would probably need to plasti-gauge the bearings. You might not have a bad ridge so you may or may not need to ream it.
chrlsful,
A wet test is when you squirt maybe a cap full of motor oil into the cylinders and then do a compression test. The oil will sit on top of the rings for a little bit so while you are doing the test it will tell you if it is your rings leaking because the wet test results will be higher than the dry test.

Jan 13, 2010 | 07:02 PM

Brigart

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Run piston to the bottom, Clean oil off the cylinder wall with some degreaser.
Tape tin foil or lint free cloth to block debri from falling in. Depending on the severity of the ridge. Some scotchbright or they make a scraper that swirls it flush again for ya. Then vacuum out the cylinder. Rinse repeat.