high compression

[Charner (MS)]

I need some input from you 8N scholars. I bought an 8N from a guy that bought it from some lady where it had sat in her barn for
around 20 years. He put on a carburetor, battery, etc. He put it for sale. I saw it and he cranked it and it ran well. I
bought it for a rebuild project. No. 56 for me. Great hobby. It had bad rubber all around. I replaced that, toke it all apart,
painted, replaced missing parts. Set the valves, put on electronic ignition (front dist.). Everything was fine. Ran
beautifully. Shut her down. And checked compression. #1-140 #2-140 #3-145 #4-155. Of all units Ive been involved about half,
25 of so, we rebuilt the engine. Compression was always from 120 - 130. The only thing I could think of was maybe the head was
shaved. I dont know, what do you think?

 

[Den N Ms]

Charner (MS) , It is a possibility it could have like M&W high compression pistons in it.Rare pistons and hard to come by.

 

[Roger in Iowa]

Tractor Supply had kits that ran domed or knuckled pistons directly in the block, no sleeves. Probably what was ran in flathead V-8 racing engines.

 

[JMOR]

(quoted from post at 14:41:36 05/21/22) I need some input from you 8N scholars. I bought an 8N from a guy that bought it from some lady where it had sat in her barn for
around 20 years. He put on a carburetor, battery, etc. He put it for sale. I saw it and he cranked it and it ran well. I
bought it for a rebuild project. No. 56 for me. Great hobby. It had bad rubber all around. I replaced that, toke it all apart,
painted, replaced missing parts. Set the valves, put on electronic ignition (front dist.). Everything was fine. Ran
beautifully. Shut her down. And checked compression. #1-140 #2-140 #3-145 #4-155. Of all units Ive been involved about half,
25 of so, we rebuilt the engine. Compression was always from 120 - 130. The only thing I could think of was maybe the head was
shaved. I dont know, what do you think?

ypically, a compression ratio increase of 30% will only yield a compression pressure increase of around 10%......so, I would try a different compression gauge myself. Since the Sherman High Compression head only brought the ratio up to 7.5 from 6.1 or 6.7, I personally don't see 20-25% pressure increase in the cards.

 

[Charner (MS)]

Thanks for your input. Interesting comments. Whatever caused the excess is just going to the buyer as is. There should not be
any problems only a more powerful engine. Thanks again.