Holy compression batman...

00fxd

Well-known member
Joined
Mar 25, 2008
Messages
549
Location
Western Canada
Just got my LQ4 to a state in my chassis where I could spin it on the starter so I could do a Compression test. The engine has sat on a shop floor for 3-4 years til I got it. The numbers were between 205 and 225 psi.! Should I be scared :shocking: Lol Pretty neat deal. Gonna be interesting once the thing is on the road.
 
I think that compression numbers are less useful in absolute terms than in relative ones because of the variables involved. If your range from lowest to highest is 20PSI (~10%) I think that's reasonably good.
 
That's a lot of cranking pressure, may need a start retard. could most likely use a longer cam, bleed off some pressure @ low rpm and gain on top.
 
I wouldn't worry, The LQ4 is the lowest compression motor in the LS/LQ series. If it's the first time it's been cranked and not fired yet, I suspect they sprayed some srorage/fogging oil in the cylinders, causing higher cranking cylinder pressures. I see it in stored boat motors too. Y ou have to get the engine started to get that oil burned out.
 
I was sorta joking when I asked if I should be scared. This is a stock engine of unknown mileage tho I am assured it is quite low. A couple of cylinders were 175psi so after siting so long I figured I'd shoot some light oil down the cylinders and they came right up too. Can anybody else check a cylinder or 2 on a 6.0 and see where theirs is at?
 
Have you started the engine? I've never got any kind of good cylinder pressure readings on cold engines.
 
Gary, no it has not been started in some years. I checked at an auto wreckers today - compression readings of 200 psi are not uncommon.
 
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