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Sloppy pistons 8n

D

Doug 13

Member
Finally pulled the head on my low compression 8n. I was suprised because you could put your fingers on the pistons and wiggle them around in their bore! In fact I could fit a .014 feeler gauge between the piston and the bore. Didn't ever think a engine could get so loose.
 
Are they all that same size? Are there sleeves in the cylinder bores? I'd say somebody installed the wrong size pistons or sleeves in the first place as .014 slop is a
mile in the world of precision fits. Somebody bought their engine kit before knowing what sizes to get. Perhaps they simply didn't know or if they did, figured, oh, well,
I'll just use them, which would be a poor decision and maybe he shouldn't be allowed around a machine shop. This why you never buy an engine kit until AFTER you get the
block to a qualified shop, boiled, then measured with a precision bore gage. The mechanic/tech will then advise and/or order what size kit to get.


Tim Daley(MI)
 
I rebuilt the engine on our '49 which was last completely overhauled in 1966 and was amazed at how little wear there was in the sleeves although it smoked like a freight train but started and ran great. I probably could have gotten by with just rings, valve grind, and oil
pump rebuild YT parts would have missed out on some sales! I still haven't gotten to the startup day yet and LAST Thanksgiving was my goal. Too many projects going at one time.
 
(quoted from post at 17:40:02 09/08/22) Finally pulled the head on my low compression 8n. I was suprised because you could put your fingers on the pistons and wiggle them around in their bore! In fact I could fit a .014 feeler gauge between the piston and the bore. Didn't ever think a engine could get so loose.
Click to expand...

Never measured up an N piston, but........many pistons are tapered from top to bottom and clearance is measured at the skirt.
 
We tore one down(trade in)and it had the tin can liners,the liners were missing.
The pistons were running in the bare block.
 

The pistons appear all the same size. I see what might be the liners. They measure about .020 thick. The starter switch is burned out and the starter is new. So the PO ground on it not knowing the pistons were undersized. When somebody told me "well maybe they forgot the rings I laughed". Hard to believe a over haul person could do that. Joke is on me! Tractor still has the tags on all tires. Basically new. Also wheel weights on all four. My cost was $0 so I'll be repairing the engine. Maybe short blocks are available. Thanks
 
...The starter switch is burned out and the starter is new... -Doug, electrical has nothing to do with the engine cylinder bores and pistons - stick to the topic at
hand. You don't need a short block -what's wrong with block you have? Piston OD and sleeve ID are all the same size on the N-Series --- 3-3/16 diameter. Some guys
seeking higher compression like for pulling didn't put sleeves (cylinder liners) in and rebored their cylinders and got bigger pistons. OEM Cylinder Sleeves were made of
steel and why the s/n's were hand stamped with a STAR prefix and suffix to indicate such. Steel Sleeves were obsolete by early 1950 and FORD went to cast iron cylinder
liners and never looked back. The s/n's were then stamped with a diamond symbol. This is a moot point nowadays because they no longer make steel sleeves anyway; all new
sleeves are cast iron. Cylinder liners come in .040 and .090 thick walls but the ID's are all the same, 3-3/16. I advise you take your block to a good engine shop who
knows vintage FORDs and have him check it out. He will get you the correct kit and can rebuild the engine correctly.


Tim Daley(MI)
 
(quoted from post at 01:40:02 09/09/22) Finally pulled the head on my low compression 8n. I was suprised because you could put your fingers on the pistons and wiggle them around in their bore! In fact I could fit a .014 feeler gauge between the piston and the bore. Didn't ever think a engine could get so loose.
Click to expand...
Yep, it s amazing how loose and engine can be and still keep running.We just got done rebuilding my neighbors 8N that was smoking real bad. We put the engine on a engine stand, and rolled it over to takeoff the rod nuts. Pulled the nuts off and the piston fell right out of the engine. Never seen that before.
 
(quoted from post at 05:40:06 09/10/22)
(quoted from post at 01:40:02 09/09/22) Finally pulled the head on my low compression 8n. I was suprised because you could put your fingers on the pistons and wiggle them around in their bore! In fact I could fit a .014 feeler gauge between the piston and the bore. Didn't ever think a engine could get so loose.
Click to expand...
Yep, it s amazing how loose and engine can be and still keep running.We just got done rebuilding my neighbors 8N that was smoking real bad. We put the engine on a engine stand, and rolled it over to takeoff the rod nuts. Pulled the nuts off and the piston fell right out of the engine. Never seen that before.
Click to expand...

I've been working on my cousins NAA. Started running like crap. Distributor needed attention. Got that R + Red. Still runs like crap.

No compression on #2 and #3. I'm surprised it still ran. I suspect the head gasket is shot between the two cylinders. That NAA still starts right up, moves around, on 2 cylinders.

When cousin cleans up head area will pull valve cover and head.....
 
(quoted from post at 04:29:34 09/10/22) ...The starter switch is burned out and the starter is new... -Doug, electrical has nothing to do with the engine cylinder bores and pistons - stick to the topic at
hand. You don't need a short block -what's wrong with block you have? Piston OD and sleeve ID are all the same size on the N-Series --- 3-3/16 diameter. Some guys
seeking higher compression like for pulling didn't put sleeves (cylinder liners) in and rebored their cylinders and got bigger pistons. OEM Cylinder Sleeves were made of
steel and why the s/n's were hand stamped with a STAR prefix and suffix to indicate such. Steel Sleeves were obsolete by early 1950 and FORD went to cast iron cylinder
liners and never looked back. The s/n's were then stamped with a diamond symbol. This is a moot point nowadays because they no longer make steel sleeves anyway; all new
sleeves are cast iron. Cylinder liners come in .040 and .090 thick walls but the ID's are all the same, 3-3/16. I advise you take your block to a good engine shop who
knows vintage FORDs and have him check it out. He will get you the correct kit and can rebuild the engine correctly.

Ok, I will look for a experienced mechanic.Thanks for the info.

Tim Daley(MI)
Click to expand...
 
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