What's your compression?

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Stubble

Active member
I did a compression check and ended up with 200 psi on #1, and 205 on the other three cylinders. This seems to me to be high. I have 400km on a rebuilt motor with 8.5:1 pistons, an HKS 1.6mm mhg, and a decked head and block. My build calculations put the compression ratio near the stock 8.8:1, but I'm beginning to doubt this now.
So, is this compression too high? Will it drop after I log some more miles? What do other people have for compression?
 
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gtfour77

New member
200 sounds about right. That's what I have now on my new motor.... I think toyota BGB says anything above 190 is good...
Hope this helps.
 
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b00staholic

New member
I just recently got 200, 210, 210, 205 on my stock motor with 76,000 miles on it.

This is with cranking the engine over 5 times.

200 is too high, the BGB does not say that anything over 190 is good...160 + 10 is "good," with somewhere around 120 being the lower limit. Sorry I can't remember the exact numbers right now, but hopefully someone who knows them will chime in.
 
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silverarrow

New member
I think it was 164 or something like that for maximum and then 128 or 126 for minimum compression. And it is unusual to see some of these all trac guys getting compression well into the high 170s-200s for compression.
 
5

5speedGT4

New member
my jdm 185 motor reads ~155psi consistantly between all 4 pistons or actually 11.4kg/cm, 11.5kg/cm, 11.5kg/cm,11.4kg/cm

well in spec..... not bad for a $900 motor!
 
R

Rick89GTS

New member
For the 165s, BGB says 128 - 178 psi or more is good with no more than 14 psi between cylinders. It just doesn't say how much more is good...
 
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SuperWhite92

New member
5speedGT4":2bqr26lh said:
my jdm 185 motor reads ~155psi consistantly between all 4 pistons or actually 11.4kg/cm, 11.5kg/cm, 11.5kg/cm,11.4kg/cm

well in spec..... not bad for a $900 motor!
Click to expand...

Nice, where'd you pick it up for $900?

I just bought mine for $1000, and the compression tests ran ~175 psi on all cylinders. Crazy, Huh? And I didn't believe the guy I bought it from when he said that. Turns out its true though
 
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gtfour77

New member
200 is great! My motor was just built and is 100% carbon free...and I had 200 on all four ...With a thicker cometic head gasket. It just means that the rings and valves seal good... That's my undestanding. I have the BGB in front of me and it says " 12.5kg/cm squared (178 psi, 1,226kPa) OR MORE"
Limit is 128 Psi with the maximum difference between cylinders 14 Psi.
I would say as long as it's not 250 or 300 Psi you're fine. The bigger the number the better seal in the rings and valves...Just my 2 cents...[/b]
 
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