Jersey Posted May 28, 2004 Share Posted May 28, 2004 and came up with 162-163 across all 6 I thought it was suppose to be around 142 max and 100 min on an '82 L28ET? If so, think it could be carbon buildup causing this much of an increase? I bought the '82ZXT donor car with 80k miles on it, owned by an older guy all it's life and was off the road for the last 10 years, since he passed away. The wife didn't know of any performance mods he may have done to it (do they ever know the half of it??? ) and it seems the motor has never been touched other than maintenance. I'm figuring maybe flattops in the F54 with the P90 is causing the raised compression values but then, why have i been able to run 16-17psi with the T3 without ping? Strange. Idea's? Quote Link to comment Share on other sites More sharing options...
aarang Posted May 28, 2004 Share Posted May 28, 2004 Could be the cam timing making the cyl pressures higher. What number is the cam gear on? Aaron Quote Link to comment Share on other sites More sharing options...
Jersey Posted May 28, 2004 Author Share Posted May 28, 2004 #1 Quote Link to comment Share on other sites More sharing options...
yo2001 Posted May 29, 2004 Share Posted May 29, 2004 I ran 8:1 150psi or so when I was running no ping. You are just good Jersey Quote Link to comment Share on other sites More sharing options...
technicalninja Posted May 29, 2004 Share Posted May 29, 2004 Your results are fine. If you did test with different compression gauge you would probably get different results. I once did multiple comp tests with different gauges in a large dealership (just to see how accurate gauges really were). Got wildly different readings. What you are most interested in is all readings at a reasonable level (for your gauge) and all cylinders within 5-10 percent of each other. Your readings are within 1 percent of each other which is excellent. Valve timing and adjustment can have a lot of effect on compression pressures. Due to your readings I would guess your valve adjustment is perfect. Check it anyway and post results. Valves too loose would increase compression readings/ too tight decreases readings. Pull a plug and check for carbon and which pistons are installed. I prefer flat tops in a turbo. The resulting 8.5/1 ratio works fine with properly modified systems and has much better off-boost response. Rick Quote Link to comment Share on other sites More sharing options...
Jersey Posted May 29, 2004 Author Share Posted May 29, 2004 I did a compression check a while ago with about the same exact readings. The other night when i posted this, i had just adjusted my valves and then checked compression. Hard to tell through the spark plug hole which pistons are in there but i'll try again. I'm sure i'll be pulling the head soon enough for one reason or another. Guess i'll find out then. There are little spots of carbon on the plugs which is why i thought carbon was causing the increased compression results. Probably multible things attributing toward it as you suggested ninja. I think my Z is pretty far from "properly modified" but so far, so good Work in progress. Thanks for the replies and info guys. Quote Link to comment Share on other sites More sharing options...
Pyro Posted June 1, 2004 Share Posted June 1, 2004 Yes, gauge accuracy could be the problem. I have two compression gages. On a recent compression test using one turbo engine and two gages, one gage read 110 and the other read 140. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted June 1, 2004 Share Posted June 1, 2004 yeah.. cheap gauges... I have a cheapo auto zone gauge, and even after I put new rings in my engine and broke them in my compression read 120psi all the way across I just look for consistency across all cylinders... then again I've no idea what gauge you're using I know my friends snap-on gauge reads way higher than mine does. Quote Link to comment Share on other sites More sharing options...
Jersey Posted June 1, 2004 Author Share Posted June 1, 2004 Using a snap-on gauge. Compared it with another cheaper brand and got the same readings. Also, just did a compression check with the same gauge about a month or so ago on my cuz's 280 after his build and the #'s were 140-142 across all 6 so, i'm thinking it's close to being correct. Thanks guys. Quote Link to comment Share on other sites More sharing options...
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