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John426 
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Joined: 14 Aug 2012
Location: France
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 Topic: Allis C compression value
Posted: 09 Apr 2019 at 11:39am |
Hi
What is the compression ratio or the PSI compression for an Allis Chalmers C distillate
On the web i see differents ratio from 70 PSI to 115 PSI . What is the correct one for distillate engine?
Mine is the tractor number 50953 , i think that production date is last quarter of year 1947
Edited by John426 - 09 Apr 2019 at 11:41am
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Leon n/c AR.
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Joined: 19 Mar 2013
Location: Heber Springs A
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Posted: 09 Apr 2019 at 11:44am |
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Several year ago when I checked our old B best I remember it was somewhere between 60-70 psi.
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John426
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Posted: 09 Apr 2019 at 11:48am |
I checked mine , i have 65 PSI on each cylinder, but my question is does it O.K or to low?
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DrAllis
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Posted: 09 Apr 2019 at 12:22pm |
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If the compression is 65 psi on ALL four cylinders, AND it runs OK, why are you concerned?? The only way to correct it is to overhaul it. It sounds like it does indeed have the distillate pistons in it. You did check the compression with the throttle set WIDE OPEN didn't you ???
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CrestonM
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Posted: 09 Apr 2019 at 12:53pm |
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Are you all talking about the dished kerosene pistons? My "B" had those, and it had 90 psi in all 4 before I overhauled it with gas flat top pistons.
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John426
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Posted: 09 Apr 2019 at 1:39pm |
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I have flat piston
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AaronSEIA
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Posted: 09 Apr 2019 at 1:51pm |
4.75 c/r is 99 lbs 5.75 c/r is 115 per the book. AaronSEIA
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Gerald J.
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Posted: 09 Apr 2019 at 8:50pm |
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Dick L
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Posted: 09 Apr 2019 at 8:57pm |
 John426 wrote:
I have flat piston |
Flat top pistons can also be low compression pistons when they do not come even with the deck when at TDC.
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steve(ill)
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Posted: 09 Apr 2019 at 9:00pm |
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Aaron............. not sure how they got those numbers...... atmospheric pressure is about 14.7 psi ................ if you had a 5:1 compression motor, you should get 5 x 14.7 or about 70 psi ................ if you had 6:1 compression, you would get about 85 psi..... I don't see how any of the small allis motors would put out 100 psi since then all had less than 7 :1 compression ...... ??????
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Like them all, but love the "B"s.
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AaronSEIA
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Posted: 10 Apr 2019 at 6:49am |
I don't know either. Just quoting the AC service manual. The BE engine was 4.67 c/r at 84 lbs and the 4.92 c/r at 94 lbs. I'm assuming "compression pressure" is on a compression test gauge. I don't think I have an I&T manual to see if they say the same thing. AaronSEIA
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