Just want to confirm my compression ratio for my LQ4 build:

Stock bore/stroke/piston LQ4
243 heads milled .017
Stock .051 thickness head gasket

I'm getting 11.1:1

Can anyone confirm my math?

Thanks in advance!

 

Valve relief on the pistons (like 4cc)? Do you know how far out of the hole the pistons are (deck clearance)? What size compression chambers on the heads? Is that about 60cc?

 

I believe the stock reliefs on an LQ4 are -2. Chambers are 61cc. This is an untouched bottom-end, so deck clearance is stock.

 

Using a typical deck clearance of 0.006" out of the hole, I get about 11:1.

 

Thank you!

 

There is a lot more than 2 cc's worth of dish on an Lq4 piston. I just have valve reliefs in my flat tops and they are 3.2 cc's. I'd say it's 6 cc's or more.

 

Stock LQ4 piston has a 7cc dish. Using that along with your info and -.006" deck height I get 10.6:1 CR.

 

THank you...

I rechecked and saw number anywhere from 6-7 cc dishes.

Thanks for catching my mistake!

 

I get around 10.6 SCR

 

dont mean to hijack but i have the same question

heres my specs:
pistons -6cc
799 heads milled .019
cc head @ 62cc
piston to deck -.013
.075 between piston and flat of head
3.905 bore
.050 thick gasket

any help would be great

thanks in advance

 

Here is a good web site to bookmark that will calculate your compression ratio:


http://www.kb-silvolite.com/calc.php?action=comp

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my pistons had a 6 cc dish and my heads were milled .015 and the chambers measured 62 cc i didnt measure my piston out of hole but i guessed them at .005 out of the hole i figured my compression to be just a little over 10.5 i am going to say you have around 10.6

 

thanks for the web site

saved it in fav's

 

Thank you! I'll bookmark that for the next build!