Cylinder Compression-psi -- 5.7L - Hemi Truck Club
 
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Old 05-07-2017, 09:30 AM   #1
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Cylinder Compression-psi -- 5.7L

The cylinder compression psi for a '04 5.7L hemi (stock) with 165K on the odometer. May have cracked a head, busted a gasket.
The Haynes manual says - not available, but pressure should not vary more than 40psi between cylinders.
Searched the forum for an answer. Redtruck-VA mentioned 180psi +/- 10 between cylinders - does that cover high mileage blocks ?

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Old 05-07-2017, 09:52 AM   #2
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Misquoted from the thread.

Quote:
Originally Posted by Redtruck-VA View Post
I've always considered all cylinders within 10 psi of one another above 140. What lead you to do a compression check? #6 is often the cylinder that has spring problems. Have you upgraded the springs yet?
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Old 05-07-2017, 10:12 AM   #3
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I think I have the answer if this '03 wasn't a rebuilt

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Originally Posted by Stanger View Post
Started doing a compression test on my 03. So far passenger side has been 180 with the exception of #6 cylnder which was 172/175. What are the normal withn range numbers suposed to be? This was a dry test.
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Old 05-07-2017, 10:48 AM   #4
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As long as all the cylinders are within 10 psi of each other it's showing normal wear. If you have a odd cylinder, then that's indicating a problem. Whenever I hear #6 mentioned I think valve spring.
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Old 05-07-2017, 11:58 AM   #5
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If it is a valve spring, get it replaced before it breaks, you may have a valve drop, causing considerable damage.
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Old 05-12-2017, 02:29 PM   #6
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Another question please. Can I run a compression check cold ?? My situation is the radiator (original 13yo) sprung a leak and it's tough to get it up to temperature with the leaking radiator.

I have pulled the plugs and they are slightly hard sticky like a varnish, I don't know what that means, but they are all the same conidition - cylinders 1-8. Waiting on someone to come home and turn the key for the compression check now.
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Old 05-12-2017, 02:42 PM   #7
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I don't see any reason you shouldn't. Pull the fuel pump fuse so your not pushing fuel.
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Old 05-12-2017, 03:04 PM   #8
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Quote:
Originally Posted by Redtruck-VA View Post
I don't see any reason you shouldn't. Pull the fuel pump fuse so your not pushing fuel.
check. Pulled the fuel pump relay and what I hope is the lead to the distributor.
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Old 05-12-2017, 03:12 PM   #9
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Distributor? What engine are you working on?
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Old 05-12-2017, 03:42 PM   #10
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Quote:
Originally Posted by Redtruck-VA View Post
Distributor? What engine are you working on?
5.7L Hemi. Was trying to find one low voltage lead for all the cylinders. and yeah i went cross-eyed trying to find a distributor or lead to the bank of plugs and coils. settled on one elec connection at front center top of block that appeared to connect to the plugs and coils.

If you hear a loud explosion there in VA, don't sweat it that's just me attempting a compression check here in TX
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