GP engine gaskets and technical data

[Unibuddy]

I'm hoping someone can point me toward a quality set of engine gaskets, crank bearings, and rings for my GP engine. I'm also interested in acquiring technical specifications for the engine as well such as standard cylinder bore, crank journal size, and any other pertinent engine measurements. I've got the engine apart bc I was having difficulty getting it to start and keep running. The compression was about 30lbs below standard and a leak down test showed the head gasket was leaking between 1,2, and 3 and the rings weren't doing much at all. Valves seemed good though. Thanks, fellas

[Michael C]

You need a manual for the 8n or 9N Ford tractor engine. It is essentially the same engine with a downdraught carburettor/manifold, and a different distributor set-up. Gaskets, etc are essentially 9N available from any vintage tractor dealer.

The pistons & rings are the same as Ford V8 - I used 4 ring pistons with the extra oil ring around the lower skirt. And since these come in sets of 8, I've got a set of four Std sized surplus to requirements, if you need them. I My engine was sleeved back to std, hence the use of std sized rings and pistons.

Mike

[Adam]

You can download the GP maintenance manual for free on jeep draw.

tm101101 is available on the auction site for 20 bucks.

Brad Gates has some of the manuals and some parts, he has a parts list

Adam

[gpwmke]

Yes you can go to any Ford/New Holland tractor dealer to get most parts for your GP engine.The engine has replaceable sleeves if you need to go that route. I may be wrong but I thought the GP/9N tractor engine used the same pistons as the Ford 110 horse power V8 which was used in the Mercury. The standard Ford V8 when the war started was the 90 horse which may have used different pistons. A tractor dealer or repair shop could easily rebuild your engine for you. If you are in Wisconsin, I can email you the place that rebuilt my GP engine.

[Michael C]

Yep, 3-3/16, 95 HP V8 engine pistons, not 3-1/6 85 HP V8 engine pistons.

Mike

[Schultzd]

GP engines do not have replaceable sleeves.

[Michael C]

GP blocks can be bored and sleeved if necessary.

Mine was.

Mike

[Schultzd]

GP blocks can be bored and sleeved if necessary.

Mine was.

Mike

Yes they can, but they do not have replaceable sleeves like the 9N engine, as stated by the other poster.

Dan

[Unibuddy]

Thanks, everyone. I blasted past the section with all the technical data in the GP manual the first time I checked. Feel like a big dummy for missing basically all the info I wanted right in front of me. I'll have her back up and running soon. I do have one question still, I was under the impression that the V8 pistons were not standard bore but that you had to be .040 overbite for standard V8 95 HP pistons to fit. Am I mistaken?

[Schultzd]

They come 10 to 40 over so, any of these should work as well.

[Schultzd]

Also standard bore.

[Michael C]

From the manuals:
GP Bore: 3-3/16 inches
GP stroke: 3-3/4 inches
GP displacement: 119.5 cubic inches
GP displacement per piston: 29.875 cubic inches

Ford 95 HP 24-head stud V8:
Bore: 3.1875 inches ( ie 3-3/16 inches)
Stroke: 3.75 inches (ie 3-3/4 inches)
Total Displacement: 239 cubic inches
Displacement of each piston: 29.875 cubic inches

Thus the GP engine as standard is exactly the same bore & stroke to the V8 as standard, and displacing exactly the same displacement per piston. Available range of oversize pistons for each engine is also the same.

Mike

[bonanza]

Tuesday, Apr 13, 2021 11:10pm
Michael C, are the four pistons still available. Need them down under to rebuild a GP engine for GP 8506.

Brian Cartwright.

[Michael C]

Brian,

Email sent.

Mike