Piston selection/compression help
Piston selection/compression help So Im building an LQ4 based engine for my third gen camaro. I have a set of 5.3 ported/larger valve heads and I was going to install them on a stock bottom end LQ4 and go to town. However it looks like my engine is going to need to be freshened up. The cylinder walls have some rust damage and will need to be overbored. I figured Id go ahead and upgrade the rods as well. Ill still be running the stock crank. I was looking at running these Mahle pistons. This will be a NA motor no nitrous. Im coming up with about 12:1 compression ratio though when i do my calculations. I think Im not calculating this right. Can someone else run the numbers as well. This was calculated with a 4.030 bore on the block with a 4.080 .051 thick gasket gm number 12610046. 62cc combustion chamber and -4cc piston. Here is a link to the pistons, http://www.summitracing.com/parts/ml...0f04/overview/ summit says they are +4cc but everywhere else shows that part to be -4cc. Any help is appreciated.
Last edited by 91Camaro1LE; Dec 16, 2015 at 02:49 PM.
No real need to go from 4.00" bore all the way out to 4.080" unless you're trying to un shroud some 2.165" valve size LS3 heads. Certain LQ blocks aren't even thick enough to do that safely.
If staying NA with no juice....I'd look for some DNJ hypereutectic pistons in .5mm (.020") or 1.0mm (.040)......they're right around 250 bucks with rings from R/A or check the classifieds for some 4.065" LS3 take outs....a buddy of mine has a set on Grand Sport Vette rods from a 1200 mile engine that perhaps he would part with........bore your block and toss a set of Hastings or Mahle rings on and call it good. Hypers are decent for mild builds, they're tighter fitting, quiet on cold start up, and consume less oil.
With the +.020" DNJ pistons I get 11.4 with the .051" gaskets
Stock GM LS3 pistons will be positive deck height by .016" on an LQ block so a .060" Cometic gasket would put you at 11.8
If staying NA with no juice....I'd look for some DNJ hypereutectic pistons in .5mm (.020") or 1.0mm (.040)......they're right around 250 bucks with rings from R/A or check the classifieds for some 4.065" LS3 take outs....a buddy of mine has a set on Grand Sport Vette rods from a 1200 mile engine that perhaps he would part with........bore your block and toss a set of Hastings or Mahle rings on and call it good. Hypers are decent for mild builds, they're tighter fitting, quiet on cold start up, and consume less oil.
With the +.020" DNJ pistons I get 11.4 with the .051" gaskets
Stock GM LS3 pistons will be positive deck height by .016" on an LQ block so a .060" Cometic gasket would put you at 11.8
Last edited by A.R. Shale Targa; Dec 16, 2015 at 02:43 PM.
sorry, ill correct my first post. let me clarify, the engine would be bored to 4.030 the head gasket used for calculating was 4.080 bore .051 thick 12610046 gm gasket.... Mahles site is saying that with 64cc heads these pistons will be about 10:7 to 1. My math must be wrong.
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I get around the same #'s as Mahle with 64 cc heads and with 62cc heads i get 10:95 to 1 but i am just using an online compression calculator. A.R. Shale Targa builds motors so i would go with the #'s he gives you.
