Low Compression rebuilt engine

[Charner (MS)]

Ford 8n history unknown. Was in owners barn 10-15 years. Said it was running well when parked. I tore it do down and completely rebuilt engine. Turned crank, pistons, sleeves, etc. When I broke it down it had no sleeves in the block. Never seen nor heard of this. I assembled the engine and cranked. Ran great. Check compression and found 1 - 90lbs, 2-90lbs, 3-100 and 4-100lbs. Ever engine Ive ever done has had 110 - 125lbs. Why? Only thing I can figure is the block was worn somewhat before it was parked and when it cranked and ran, got hot, the sleeves expanded and in effect indicated excessive wear and lower compression. What do you think?

 

[Bruce (VA)]

So you installed sleeves in the bare block w/o re-boring it?
75 Tips

 

[TheOldHokie]

(quoted from post at 17:10:10 11/30/21) Ford 8n history unknown. Was in owners barn 10-15 years. Said it was running well when parked. I tore it do down and completely rebuilt engine. Turned crank, pistons, sleeves, etc. When I broke it down it had no sleeves in the block. Never seen nor heard of this. I assembled the engine and cranked. Ran great. Check compression and found 1 - 90lbs, 2-90lbs, 3-100 and 4-100lbs. Ever engine Ive ever done has had 110 - 125lbs. Why? Only thing I can figure is the block was worn somewhat before it was parked and when it cranked and ran, got hot, the sleeves expanded and in effect indicated excessive wear and lower compression. What do you think?

I don't think yourr problem is expanded sleeve - we are talking a miniscule clearance at most. I assume they were reasonably tight when you installed them. If not you may have dropped one or more. Did you use a sleeve retainer when you installed the sleeves? New pistons and sleeves? What about valves?

TOH

 

[Dennis P]

Sounds to me like a valve issue. Did you install new valves, guides, and had seats ground ( not lapped)?

 

[ASEguy]

You said it runs great. Compression specifications vary with different engines. Did you use the tractor long enough to seat the rings? With all due respect, rings need to be seated according to the ring maker instructions. They will give you a procedure to ensure the rings are properly seated. Compression testing should be done on a warm engine with the throttle blocked open and the air filter not connected. I addition to that, you must have adequate cranking speed.
Issues with the starter circuit can affect the readings if it is cranking slow.

 

[Charner (MS)]

Replies. Rings were set properly. Engine ran an hour or so. Engine was hot, plugs removed so engine would spin faster. Valves were ok. Only ground and set them. Sleeve went in with only a hand push. Had to use plenty of sleeve retainer to secure them. I did not bore the sleeve. If I had would have had to go with thick wall sleeve. I can't say how many engines I've rebuilt and all were compression tested the same way and always got 115 -125 lbs. except this time. At any rate this one is going on the market as is. Don't known what else to do.

 

[Hobo,NC]

I have only checked a few out of curiosity before I fired them up around 100 is what I got. Maybe yours will get better as the rings seat in.

 

[Bob - MI]

Have you tried checking compression after squirting some oil into the cylinders to see if that has any impact?