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Old 09 Nov 2014, 03:58 pm
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Default Math Problem

I stink at math but i do know max variation between cylinders on compression is 25%. Now I am getting 195 200 190 185 compression readings. Dose that fall in the 25% range? This is with a dead cold engine. 130k on engine. Just put a new head gasket in.
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Old 09 Nov 2014, 04:17 pm
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Default Re: Math Problem

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Originally Posted by scatgo1 View Post
I stink at math but i do know max variation between cylinders on compression is 25%. Now I am getting 195 200 190 185 compression readings. Dose that fall in the 25% range? This is with a dead cold engine. 130k on engine. Just put a new head gasket in.
The highest is *195 lowest 185, 195 x .75 = 146.25 which would be 25%

Your *200 is either inaccurate or you have a lot of carbon or a valve overlap problem with the cam shaft timing.
Then your post from cyd #1 left to right.. #1 and #2(if 2 is actually corrected 195) look good #3 and #4 185 (190x.75+142.50) 185 x.999=184.81/round up 185 which is 1%

You should really re-due your compression check:
Do no more than 5 engine cycles per cylinder.
Make sure the throttle body is wide open


If you get #1-4 with 190+/-10psi you have a pretty good result.

You could follow up by doing a wet compression test and then even a cylinder leak down for a total engine analysis.
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Last edited by NitroPT; 09 Nov 2014 at 04:38 pm. Reason: spelling and added the word round up
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Old 09 Nov 2014, 06:57 pm
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Default Re: Math Problem

Thanks. I did that test with the upper intake manifold off. And when I spun the engine I counted 10 compression strokes.
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Old 09 Nov 2014, 07:04 pm
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Default Re: Math Problem

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Originally Posted by scatgo1 View Post
Thanks. I did that test with the upper intake manifold off. And when I spun the engine I counted 10 compression strokes.
10 is way to many no more than 5 maximum.

You have my number call if you need help anytime!

be prepared I see a member that has long story responses on threads replying as we read this.
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Old 09 Nov 2014, 08:43 pm
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Default Re: Math Problem

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Originally Posted by NitroPT View Post
The highest is *195 lowest 185, 195 x .75 = 146.25 which would be 25%

Your *200 is either inaccurate or you have a lot of carbon or a valve overlap problem with the cam shaft timing.
Then your post from cyd #1 left to right.. #1 and #2(if 2 is actually corrected 195) look good #3 and #4 185 (190x.75+142.50) 185 x.999=184.81/round up 185 which is 1%

You should really re-due your compression check:
Do no more than 5 engine cycles per cylinder.
Make sure the throttle body is wide open


If you get #1-4 with 190+/-10psi you have a pretty good result.

You could follow up by doing a wet compression test and then even a cylinder leak down for a total engine analysis.
Hey Nitro. If a Pt Crusier left LA at noon traveled at a average speed of 55, blew a head gasket and got laid up for 48 hours for repairs what time would it get to NYC......LOL
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Last edited by scatgo1; 09 Nov 2014 at 08:58 pm.
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Old 09 Nov 2014, 10:16 pm
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Default Re: Math Problem

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Originally Posted by scatgo1 View Post
Dose that fall in the 25% range?
And if it's 26% are you going to replace the engine??

Taking compression in absence of issues is a fool's errand!
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Old 09 Nov 2014, 11:54 pm
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Default Re: Math Problem

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And if it's 26% are you going to replace the engine??

Taking compression in absence of issues is a fool's errand!
And how was Rome built? Brick by brick!

A compression check is always a good start. I have always included this with any vehicle new I ever owned.
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Old 10 Nov 2014, 12:40 am
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Default Re: Math Problem

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Originally Posted by scatgo1 View Post
Hey Nitro. If a Pt Crusier left LA at noon traveled at a average speed of 55, blew a head gasket and got laid up for 48 hours for repairs what time would it get to NYC......LOL
Its a trick question

The answer is the same time.
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Old 26 Nov 2014, 09:03 pm
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Default Re: Math Problem

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Originally Posted by UptownSport View Post
And if it's 26% are you going to replace the engine??

Taking compression in absence of issues is a fool's errand!
Had a big issue. When replacing head gasket the gasket surface on top of the engine didn't look all that good. Now we know how good it is.

I think I hold out till its 27%
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Last edited by scatgo1; 26 Nov 2014 at 09:05 pm.
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