Compression test results normal?
Thread Starter
Racer
Joined: Jan 2007
Posts: 447
Likes: 11
From: New York
Compression test results normal?
Im going to get a supercharger but first i did a compression test to see if i need to forge the bottom end or if i can play with the stock ls2 this summer and forge the engine next winter.
the results
Driver side, front to back:
188
187
188
174
Passenger side, front to back:
188
190
188
193
the engien i stock but with high miles. (oil pressure is fine) but i dont know the oil consumption becous i just bought it.
Is 174 psi to low?
the results
Driver side, front to back:
188
187
188
174
Passenger side, front to back:
188
190
188
193
the engien i stock but with high miles. (oil pressure is fine) but i dont know the oil consumption becous i just bought it.
Is 174 psi to low?
Burning Brakes
Joined: Jun 2013
Posts: 867
Likes: 26
From: SW Ohio
Don't know what stock CR is spec's at (presume 190-195) but the variability isn't that bad. Typically, you want a deviation of no more than 10% between low and high cylinders, so 193-174 = 19, which is right on 10%. A low reading of 174 on a high-mileage block sounds pretty damn good to me. If it hasn't been using excessive amounts of oil, I'd say you're good to go.
You can always go back and put some oil in the low cylinder and run another check. You'll know whether it's ring- or valve-related.
You can always go back and put some oil in the low cylinder and run another check. You'll know whether it's ring- or valve-related.
Last edited by icntdrv55; Dec 26, 2013 at 09:11 AM.
Burning Brakes
Joined: Jun 2013
Posts: 867
Likes: 26
From: SW Ohio
Good point and I agree. I didn't pick up on what the OP was asking…just figured he was looking for an opinion on the overall condition of the motor. From what has been posted on the forum about the sturdiness of the LS2/LS3 motors, I presume they'll hold up to a mild-moderate SC without lots of expensive bottom end mods.
Racer
Joined: May 2012
Posts: 259
Likes: 5
looks good to me, usally like them within 5 psi of each other but thats in a ideal world. usally around 650-700 rwhp on the stock block . is fairly safe. but seen some let go alot higher and alot lower but tons holding at that power
Last edited by dekan513; Dec 26, 2013 at 10:08 AM.
Instructor
Joined: Apr 2013
Posts: 236
Likes: 0
From: CT
174 psi for what? I hope not oil pressure.....haha.
And when you say high mileage how much?
IMO those results are fine. Not a lot of deviation like someone else said.
Is this a auto or stick?
Not sure what your plans are but if you throw on a A&A or ECS base kit and run like 7-9 lbs or however much they do I'm sure you'd be safe for a while around the 550-600 rwhp mark.
And when you say high mileage how much?
IMO those results are fine. Not a lot of deviation like someone else said.
Is this a auto or stick?
Not sure what your plans are but if you throw on a A&A or ECS base kit and run like 7-9 lbs or however much they do I'm sure you'd be safe for a while around the 550-600 rwhp mark.
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Burning Brakes
Joined: Jun 2013
Posts: 867
Likes: 26
From: SW Ohio
If you do another compression check (warm engine, WOT), recheck the initial reading and then squirt a small amount of oil (motor oil) into the cylinder thru the spark plug hole and crank the engine for another check. If the reading improves, the low reading is likely a ring issue. If the reading doesn't change appreciably, it's likely top end (valve/seals).
Race Director
Joined: Aug 2005
Posts: 13,592
Likes: 187
From: Hudson WI
NCM Sinkhole Donor
Drive it and enjoy it, a blower with 130K is troubling waiting to happen.
Just my opinion.
Advanced
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From: Valley Forge PA.
Melting Slicks
Joined: Jul 2010
Posts: 2,999
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From: Surprise, Az
You may also consider doing a leak down test where the engine is cranked as in a compression test but then allowed to sit to see how quickly the pressure bleeds off.
With 130000 miles, if you want more power I would consider a rebuild with power adders. You have a good strong block to start with so it may be less expensive than running it until something major happens and them rebuilding. OTOH, if you're happy with what you have than just drive it normally. Should have a lot of life left if driven normally. Track use is another issue. The so called 'spirited'...that is what tracks are for.
With 130000 miles, if you want more power I would consider a rebuild with power adders. You have a good strong block to start with so it may be less expensive than running it until something major happens and them rebuilding. OTOH, if you're happy with what you have than just drive it normally. Should have a lot of life left if driven normally. Track use is another issue. The so called 'spirited'...that is what tracks are for.
Burning Brakes
Joined: Dec 2001
Posts: 1,244
Likes: 13
From: Laguna Woods, CA
Premium Supporting Vendor
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From: Providing the most proven supercharger kits for your C5/6/7 609-752-0321
Otherwise if the engine is holding up fine, I would not hesitate to supercharge a higher mileage engine. We have supercharged cars with more miles then that. We have one customer who we supercharged at 105k come back for a cam and meth at 225k.
This can be taken as jaded since we manufacture supercharger kits, but I'm going off of past results. Some engines last forever and some fail quickly, if your not prepared to possibly build an engine at any milage, then don't supercharge the car ever.