checking clyinder pressure
04-20-2006, 06:18 PM
#3
well I figured the spark plugs...OBVIOUSLY
Can they all be out? what about the exhaust? can it be off of the car?
I am not doing a leak down test...I have a screw in pressure gauge that goes into the spark plug holes to check for cranking compression.
I was wondering what the proper technique was and what kind of pressure I should be showing.
I thought around 200 psi was considered good.
Can they all be out? what about the exhaust? can it be off of the car?
I am not doing a leak down test...I have a screw in pressure gauge that goes into the spark plug holes to check for cranking compression.
I was wondering what the proper technique was and what kind of pressure I should be showing.
I thought around 200 psi was considered good.
04-20-2006, 09:14 PM
#4
I was KIDDING about the spark plug (ergo the "DOH").
If you are checking compression, you can look up some values, but the main thing if uniformity across the # of cylinders.
Doesn't matter wether exhaust or intake is connected.
All your doing is checking how well your valves are seating and if the leakage past the rings is ok.
I would remove all the plugs as it makes it easier to turn over.
Hope that helps
If you are checking compression, you can look up some values, but the main thing if uniformity across the # of cylinders.
Doesn't matter wether exhaust or intake is connected.
All your doing is checking how well your valves are seating and if the leakage past the rings is ok.
I would remove all the plugs as it makes it easier to turn over.
Hope that helps
04-20-2006, 09:40 PM
#5
I knew you were kidding...no biggie
I was gonna do it before I got the car back together after the h/c swap.
I should turn it over with the starter 4 or 5 times and take the highest reading? Take out the fuel pump fuse etc? all plugs out and exhaust off (makes it easier)
this sound ok?
thanks a lot
I was gonna do it before I got the car back together after the h/c swap.
I should turn it over with the starter 4 or 5 times and take the highest reading? Take out the fuel pump fuse etc? all plugs out and exhaust off (makes it easier)
this sound ok?
thanks a lot
04-20-2006, 09:43 PM
#6
When I was running 8.34 dynamic compression, I got 200 psi.
With my current cam (in signature), my DCR is 8.78:1 and my cranking psi is 245!
With my current cam (in signature), my DCR is 8.78:1 and my cranking psi is 245!
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2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2018 Cadillac Escalade 6.2L A10 Pat G tuned.
LS1,LS2,LS3,LS7,LT1 Custom Camshaft Specialist For custom camshaft help press here.
Custom LSX tuning in person or via email press here.
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04-25-2006, 12:58 PM
#9
Thats wierd as hell, my 5.0 got 150 psi on all cylinders and I have 10.5:1 comp but I do have 4* valve overlap. Most stock 5.0's get 130-160psi. What is with these insane #'s you LS1 guys get?
04-25-2006, 07:46 PM
#10
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10.5:1 is your static compression ratio, they were refering to Dynamic Compression Ratio, so they are actually running more compression than you are. There are a lot of variable that effect DCR but they are probably in the neighborhood of 11.xx SCR.
04-25-2006, 08:20 PM
#11
still dont understand, your LS1 has 10.25:1 from the factory. I have 10.5:1 why do i get 150psi from a compression check and you guys get 200+ ? Before you say mine is worn out, its new block, pistons, rings, heads, etc. and i was withing 5psi on all cylinders. *confused*
04-25-2006, 08:39 PM
#14
Originally Posted by Stanger88
still dont understand, your LS1 has 10.25:1 from the factory. I have 10.5:1 why do i get 150psi from a compression check and you guys get 200+ ? Before you say mine is worn out, its new block, pistons, rings, heads, etc. and i was withing 5psi on all cylinders. *confused*
The other problem is that you have a Ford and are on a GM board
J/K
04-25-2006, 09:05 PM
#16
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i think it said like 20 in my book but it is for 04 trucks not 02 vettes lol. but why would they all be consistant but the two. and those two had like oil on the threads of the plugs.?
04-25-2006, 09:34 PM
#17
if you see a 40PSI variation you should be worried. take a turkey juice injector (whatever you chefs call it, works for me...) and squirt some oil in the low cylinders and test again, if the #'s shoot up, if so...rings...
04-25-2006, 09:50 PM
#19
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my book didn't say thats what i'm trying to figure out. my compression is a little higher than stock though i have the felpro .045's or what ever can't remimber the exact number but they are the thin ones lol. i could smell fuel when i done those two i was wondering if the left over fuel in the rails could have leaked passed the injectors when i was cranking over the eng because the fuel pump relay was pulled but not the injector fuses. and the fact i found oil on the two plugs that were the highest. could a valve seal leak cause oil to get in the cylinders and cause a false high reading??
04-25-2006, 10:09 PM
#20
4.8, when I checked my 5.0 1 cylinder was lower than the others (135ish). I put it all back togather and cranked her over for a few minutes and then pulled THAT plug and got 135 (all plugs now in, #'s will be lower) and then pulled the highest and it had 135 as well with the other 7 plugs in. Fuel on the walls can cause loss of compression during a check.
PS. it backfired like a 12 gauge when I cranked it the nexxt time
PS. it backfired like a 12 gauge when I cranked it the nexxt time