Farm Equipment - "B" engine questions.

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"B" engine questions.

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Category: Allis Chalmers
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URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=44045
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Topic: "B" engine questions.

Posted By: SteveC(NS)
Subject: "B" engine questions.
Date Posted: 18 Jan 2012 at 7:40pm

Does anyone know what sort of increase in HP an 6.5 to 7.5 compression ratio would produce in a "B" engine?
Is it possble to acheive this by milling the head?
How much would you have to remove?

Replies:

Posted By: Dick L
Date Posted: 18 Jan 2012 at 8:40pm

I have not worked it out because it is not as simple as just using the calculations.

Read the information at the link.

http://www.carcraft.com/techarticles/calculate_compression_ratio/index.html" rel="nofollow - http://www.carcraft.com/techarticles/calculate_compression_ratio/index.html

I don't put a head back on any of my B's or C's with out removing at least .150 . I have removed .200 off two heads without a problem. You might be able to take more off but I start to feel uneasy about removing more than .200. As I mill the heads I keep check the wall thickness in the water openings to the block. If someone had removed .150 and you decide to go for the .200 you might just strike water over a piston when she would get warm.

After removing the .150 you can tell a difference in the sound of the engine.

Posted By: dallasallis
Date Posted: 18 Jan 2012 at 8:42pm

I have removed .100 without any issues

Posted By: Steve in NJ
Date Posted: 19 Jan 2012 at 9:03am

When I did my B engine over bout' 10 years ago, I took Dicks advise and had .80 taken off the head. With the larger piston's, she does bark a little louder that's for sure! Had to put the muffler back on again. The straight pipe was a bit on the loud side. I think its my older age setting in now. And I used to pilot a Dragster years ago. Go figure... LOL!

mailto:Steve@B&B" rel="nofollow - Steve@B&B

Posted By: Dick L
Date Posted: 19 Jan 2012 at 11:25am

Ten years ago, Huh? I didn't know that you, er we, were that old.

Posted By: SteveC(NS)
Date Posted: 19 Jan 2012 at 11:40am

Dick, thanks for the info I shoulda asked about a CA not a B. It's also a 3.4375" bore.

I CCed the head at 70cc (4.2716 cu.in.) and I sorta guesstimated the bore space above the piston including the gasket to be 4cc (.245 cu.in.) and the swept volume is 532.124cc

(32.4722 cu.in.).

I got 8.287 to 1 compression which sounds like what I wanted to shoot for so no wonder it had a "bark" to it when the governor called for juice.

The only thing I can see is the 3.4375" pistons have more height than the stock 3.375 6.2-1 pistons have. The ones I have have an arrow facing the front of the block stamped into them.

I measured about .032" from piston top to block surface, does that sound stock?