351W on stand - What should I replace?
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Trailering
Joined: Oct 2019
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351W on stand - What should I replace?
I'm getting into the car painting and bodywork business, and a friend offered a 1991 F250 as a starting project. I ended up getting talked into doing a restoration instead of just a paint job. While driving the truck home, it ran great, if lacking in power. I tested the cylinders, and it turns out the middle two on the driver's side have no compression, so I figure that between them is a cracked head or bad gasket. Right now the whole truck is disassembled, and the engine is on a stand. I don't know how many miles are on it, since the odometer has only five digits on it and the previous owner doesn't know if it's rolled over.
My question is, how should I take advantage of the fact that the engine is on the stand? What should I definitely replace? What should I check on? And what can I probably leave alone?
Thanks.
My question is, how should I take advantage of the fact that the engine is on the stand? What should I definitely replace? What should I check on? And what can I probably leave alone?
Thanks.
Logistics Pro
Joined: Mar 2011
Posts: 4,197
Likes: 558
From: Central Wisconsin
If you have it on the stand, you might as well pull the heads off and see what the cylinders look like. If they are pretty hashed, get the thing bored and put it back together. No reason not to go through it. Should be able to keep the rotating assembly, but might have to have the pistons changed to match the new bore if you need to go that route. If the cylinders look good, I would still put new bearings in it, new rings, a new oil pump, and new seals everywhere.
Logistics Pro
Joined: Aug 2014
Posts: 3,558
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When you did the compression test, did you pull all plugs, and have throttle wide open?
I recently did a compression test with engine on floor, previous owner had tape over top of lower intake which I didn't remove, was getting no compression.
Removed the tape, allowed engine to breath, compression came up as expected.
Also, if you put oil down the cylinders with no compression, does the compression come up. This would indicate piston compression ring problem, if compression comes up. Head gasket, cracked head, cracked cylinder if still no compression, bent valve. If its on the stand, remove heads, inspect, replace head gaskets.
You must determine cause of no compression. No compression is probably worse than 'low' compression.
I recently did a compression test with engine on floor, previous owner had tape over top of lower intake which I didn't remove, was getting no compression.
Removed the tape, allowed engine to breath, compression came up as expected.
Also, if you put oil down the cylinders with no compression, does the compression come up. This would indicate piston compression ring problem, if compression comes up. Head gasket, cracked head, cracked cylinder if still no compression, bent valve. If its on the stand, remove heads, inspect, replace head gaskets.
You must determine cause of no compression. No compression is probably worse than 'low' compression.
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