Compression Ratio?

[WARLOCK]

Anyone know what the Compression Ratio would be for an LQ4 with 243 Heads?

[Sizzle Chest]

64cc chambers will bump you up to about 10:1 on an LQ4.

[WARLOCK]

Thank you sir

[WARLOCK]

So t would be the same as a lq9

[George C]

LQ4 with 243 is 10.5
LQ9 with 243 is 10.9

[Sizzle Chest]

I think thats too high. Show me your inputs into a compression ratio calculater that get you there. I went round and round on this when I was milling my heads because if you search the forums you will get wide ranging answers. Below is my attempt to quantify it for myself. Unless I am doing something wrong, I think you need 60 cc chambers to get to 10.5:1 assuming a stock head gasket.

http://www.ls1truck.com/forums/mecha...ion-ratio.html

[George C]

I think thats too high. Show me your inputs into a compression ratio calculater that get you there. I went round and round on this when I was milling my heads because if you search the forums you will get wide ranging answers. Below is my attempt to quantify it for myself. Unless I am doing something wrong, I think you need 60 cc chambers to get to 10.5:1 assuming a stock head gasket.

http://www.ls1truck.com/forums/mecha...ion-ratio.html

this has been the CR rule for years

a ls1 is 10.1 with 67 cc heads you toss on Ls6 heads and it becomes 10.5 which is the stock LS6 motor CR

just like a ls1 with 61 cc heads [5.3 heads] becomes 11.1

LQ9 and LS2 are same motors minus the heads.. a 72 cc vs 64.5 toss 64.5 on a LQ9 and you get same SCR as LS2

just like a 4.8/5.3 with 243 is 9.1
sme as 4.8/5.3 with 241 is 8.8
same as 4.8/5.3 with 317 is 8.4

i used to know the formula off top of my head. these numbers been proven over and over and over again.

[WARLOCK]

Thanks Quik glad to see you posting again.

[Sizzle Chest]

this has been the CR rule for years

a ls1 is 10.1 with 67 cc heads you toss on Ls6 heads and it becomes 10.5 which is the stock LS6 motor CR

just like a ls1 with 61 cc heads [5.3 heads] becomes 11.1

LQ9 and LS2 are same motors minus the heads.. a 72 cc vs 64.5 toss 64.5 on a LQ9 and you get same SCR as LS2

just like a 4.8/5.3 with 243 is 9.1
sme as 4.8/5.3 with 241 is 8.8
same as 4.8/5.3 with 317 is 8.4

i used to know the formula off top of my head. these numbers been proven over and over and over again.

I hear you and what you are saying makes some sense, but there are a lot of folks that would disagree with you on other forums. Rick@synergy on pt.net as an example. Dont know him personally but he makes his living doing this so I have to give him some credibility. His numbers are almost spot on with mine.

Im not a machinist so I cant say for sure. But I think the approach I used with the compression calculater is reasonable and I am sticking with my number until someone proves me otherwise. Like I said, I had a heck of time researching this because there is conflicting information out the wazoo.

[George C]

here just cause a person is of buisness doesnt mean they know what they are doing. Any person can have a buisness. not knocking anyone speaking in general

here is a calculator

Engine Size and Compression Calculator

i stand corrected its 10.4 not 10.5

the drop from 72 to 64.5 cc in head is a gain of almost .9