Compression reading ???? - Team Camaro Tech
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post #1 of 9 (permalink) Old Mar 16th, 10, 02:31 PM Thread Starter
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Chad
 
Join Date: Nov 2009
Location: Stl
Posts: 65
Compression reading ????

I bought a used 396 and have a few concerns.

Did a comp. test here are the results
1 - 180 2 - 210
3 - 190 4 - 190
5 - 190 6 - 210
7 - 190 8 - 210
Also #1 exh. port is a bit rusted where as all others have black soot.
I did a cylinder leak down test and all were very close but #1 did have 14 psi leakdown and other averaged around 12 so very close in my opinion.

I had a troubleshooting nightmare on my small block and really want to get any issues handled while this engine is out before I install it. I also prefer not to tear it all apart as its all together and ready to drop in.
What are your thoughts ?
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post #2 of 9 (permalink) Old Mar 16th, 10, 02:43 PM
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Ron
 
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Re: Compression reading ????

It's hard to say with any used HI-Mileage Engines but that looks pretty respectable. I would take all the Plugs out and pour about and ounce of Rust Check or Tranny Fluid in each Cylinder and Spin her over and let her set a couple days and do another Compression and Leak Down. Cylinder Bores can Rust Cylinders particularly if the Car has been sitting for awhile as open Exhaust Valves with the Exhaust System on the Engine create condensation which rises into the Combustion Chambers - Often Cylinders can live a long time with Rust Pits but usually leads to early Ring Failure. History of the Engine is IMPORTANT.

If your not satisfied with the results, tear her down for a Hone, New Rings, Bearings, Timing Chain. Oil Pump, and Gasket Kit. Touch the Valve Seats and Resurface the Valves and check the Guides and put in New Springs, Possible New Cam and Lifters - Then you know for sure and good to go for another 60,000 miles or more ;o)

What's the Timing Chain Slack ?

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Last edited by Z15CAM; Mar 16th, 10 at 02:56 PM.
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post #3 of 9 (permalink) Old Mar 16th, 10, 03:12 PM Thread Starter
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Chad
 
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Re: Compression reading ????

Engine is supposed to only have 200 miles tops and looks very new and clean. Thats why I am worried because as new as it all looks minus some dust from sitting for 5-6 months. Dont feel any slack in the chain at all. The motor looks very fresh, I must admit the rusty #1 exh. port has me worried as thats the cylinder with lowest compression. I emailed prev. owner will see what he says.
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post #4 of 9 (permalink) Old Mar 16th, 10, 03:18 PM
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Ron
 
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Re: Compression reading ????

Siish! You have a NEW Engine. Ensure the Tappets are Set, Prime her and fire her up. Look for possible FT Cam Lobe Failure. Ask your seller what the build consisted of and take it from there; other words, you would not have bought it.

I can't understand if your capable of performing reliable Compression and Leak Down (Time with a Stop Watch to leak say 120Lb's Pressure to 50 lbs per Cylinder - NOT what it Holds) why you would be worried about a little rust in an Exhaust Port. If your that concerned about the Sellers Reliability , pull the Heads and look at it and take note of the Piston (Dome Volume Casting/Forged) and CC the Chamber Volume to determine Static Compression for future Cam Installations.

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Last edited by Z15CAM; Mar 16th, 10 at 03:36 PM.
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post #5 of 9 (permalink) Old Mar 16th, 10, 04:01 PM Thread Starter
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Chad
 
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Re: Compression reading ????

Only worried about the rust because all other cylinders look the same full of black soot and this one sticks out like a sore thumb and happend to have the lowest compression 180lbs and the most leakdown. I know 10% is the rule for compression drop across the board and I am at roughly 16%.Honestly I just fought an issue on the small block I removed and dont really want to rip a motor apart that I just paid good money for. Thats why I want to get some opinions. I would assume from sitting for a while that could throw things off and perhaps also rust the exhaust port but thats why I am asking.
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post #6 of 9 (permalink) Old Mar 16th, 10, 04:55 PM Thread Starter
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Chad
 
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Re: Compression reading ????

Motor has been out of his car since last june/july. I assume sitting that long could throw some comp. #'s off and may be caused rust in the exh. port. He stands by his word that the motor ran great and seems trustworthy. There was still coolant and fairly clean oil in it with no signs of mixing.
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post #7 of 9 (permalink) Old Mar 16th, 10, 04:57 PM
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John
 
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Re: Compression reading ????

Chad what's with you and #1 cylinders?? I dont think there is anything wrong, probally
just the way it was stored. Maybe someone rubbed the carbon off that port a few months ago?
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post #8 of 9 (permalink) Old Mar 16th, 10, 05:03 PM Thread Starter
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Chad
 
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Re: Compression reading ????

Honestly I have no idea but as soon as I saw a #1 potential problem I started freaking out !!! The small block problem I had was a nightmare from hell so I just dont want that again !!!!!!
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post #9 of 9 (permalink) Old Mar 16th, 10, 05:21 PM
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John
 
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Re: Compression reading ????

Understood!!!
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