Help LS1 corvette heads on a 5.3

[Tooquick2beslo]

hey not sure if this goes here but here goes.
I got some 5.7 ls1 heads for cheap and I have a 5.3 motor in my truck.
I was wondering can i put these heads on my truck and what should i mill them to get 9.5-10.0 compression. Thanks for any help.
J.

 

[c4c5specialist]

hey not sure if this goes here but here goes.
I got some 5.7 ls1 heads for cheap and I have a 5.3 motor in my truck.
I was wondering can i put these heads on my truck and what should i mill them to get 9.5-10.0 compression. Thanks for any help.
J.

HI there,
Based on head quench area, you should be well over this without decking the head. LS1 stands at 10.1 to 1, so with the smaller area, the compression static will go up.
Also, be aware, if you deck the head too much, you will have pushrod length problems.
Allthebest, c4c5 :eek

 

[Tooquick2beslo]

I think that the compression would go way down considering that im putting bigger valves on a smaller engine. Im putting this on my 5.3 truck motor. Everyonen else that i have talked to are saying that I need to mill the head. I really dont want to but looks like im going to have too. Thanks for the help.
J.

 

[c4c5specialist]

I think that the compression would go way down considering that im putting bigger valves on a smaller engine. Im putting this on my 5.3 truck motor. Everyonen else that i have talked to are saying that I need to mill the head. I really dont want to but looks like im going to have too. Thanks for the help.
J.

Hi there,
Your valves have no bearing on static compression ratio. They only involve flow.
If you look at the technical specs of the 5.3 truck engine, you will see that the compression ratio 9.59 to 1 is due to less quench area and reduced bore size of the 5.3. Bore and stroke is 96.0 by 92.0. LS1 class engines are 99.0 bore by the same 92.0 stroke. So, conclusion is following.
The internal quench area is smaller on the LS1 class heads, due to more aluminum casting inside the combustion area of the head. If the heads were NOT the cause of the issue, and the LS1 heads had lowered compression ration, would it not be less than the 5.3 9.59 to 1??????????? Especially given the fact that the LS1 has a larger bore, and thus more volume of air/fuel mixture to compress???????
I would seriously reevaluate your position on this, based on factual GM service technical specifications.
Allthebest, c4c5 :eek

 

[VETTEX2]

Hi there,
Your valves have no bearing on static compression ratio. They only involve flow.
If you look at the technical specs of the 5.3 truck engine, you will see that the compression ratio 9.59 to 1 is due to less quench area and reduced bore size of the 5.3. Bore and stroke is 96.0 by 92.0. LS1 class engines are 99.0 bore by the same 92.0 stroke. So, conclusion is following.
The internal quench area is smaller on the LS1 class heads, due to more aluminum casting inside the combustion area of the head. If the heads were NOT the cause of the issue, and the LS1 heads had lowered compression ration, would it not be less than the 5.3 9.59 to 1??????????? Especially given the fact that the LS1 has a larger bore, and thus more volume of air/fuel mixture to compress???????
I would seriously reevaluate your position on this, based on factual GM service technical specifications.
Allthebest, c4c5 :eek

;stupid