LQ4 piston dish?
#1
LQ4 piston dish?
after repeated searches and literally days of searching the internet i CANNOT find a solid answer. i've seen -6, -6.5, -6.7, -7, and -8 cc as answers. wtf? who can answer this question with complete and utter confidence? i need help determining piston to valve clearance, head gasket thickness, how much to mill the head etc etc i am running out of patience.
#2
EngineKits.com has OEM replacement pistons for the Vortec 364ci which could be the LQ9 or LQ4. But it says .048" dish and given that the LQ9 is a flattop I'd assume that they're for the LQ4 and that is the same dish size as the stock pistons.
#3
Well what do we know? Since 1999 the LQ4 has had 9.4:1 compression. 317 heads have always had 72cc chambers. The stock head gasket is still .052" thick compressed right? With a little math you can figure out the stock piston dish pretty close.
Just playing with an online compression calculator...
Perfect flat tops with 0 dish comes out to 10.01:1. Coincidence of an LQ9?
-5cc gets us to 9.501:1. Close but no cigar yet.
-6cc gets us to 9.405:1 Close enough?
-6.5cc gets us to 9.358:1....GM might round that up.
-6.7cc gets us to 9.340:1 Surely GM wouldn't round that up to 9.4.
-7cc gets us to 9.312:1....Again GM wouldn't round that up.
-8cc just makes the calculations even further away.
Chance are -6cc is correct, but that's just letting math guide us.
Edit: I just realized how old this thread was. Hopefully it'll help somebody down the line who searches for this info.
Just playing with an online compression calculator...
Perfect flat tops with 0 dish comes out to 10.01:1. Coincidence of an LQ9?
-5cc gets us to 9.501:1. Close but no cigar yet.
-6cc gets us to 9.405:1 Close enough?
-6.5cc gets us to 9.358:1....GM might round that up.
-6.7cc gets us to 9.340:1 Surely GM wouldn't round that up to 9.4.
-7cc gets us to 9.312:1....Again GM wouldn't round that up.
-8cc just makes the calculations even further away.
Chance are -6cc is correct, but that's just letting math guide us.
Edit: I just realized how old this thread was. Hopefully it'll help somebody down the line who searches for this info.
Last edited by InchUp; 12-04-2008 at 04:48 PM. Reason: whoops old thread.