k_cash1432

iTrader: (9)

Just looking for some input i have a 5.7 LS1 shortblock that im thinking about sticking into my car. I have a set of 5.3(863?) heads on my old motor and I know the 5.3 heads have a smaller combustion chamber, so if i mill the 5.3 heads a lil ~.001-.003~ and use my LS6 cam&intake What kind of numbers would I be looking at? Not nessacarly going all out just gonna do a full port and polish for better flow. Am i just dreaming up a disaster?

mark21742

Nope no disaster, lots of people run the ported 5.3 heads. Are you planning on doing the port work, or sending them out to have them professionally done?

k_cash1432

iTrader: (9)

no im gonna do em my self. done a few sbc heads figure i chould get my hands on something different. I thought i was supose to use different sandpaper's when doing aluminum heads?

01ssreda4

iTrader: (96)

Send em off. My .02.

k_cash1432

iTrader: (9)

I would like to send em off but im too much of a DIY, always looking to expand my knowledge and trydoing something new...

dodson55

iTrader: (18)

you need to put ls1 intake valve in them as well

01ssreda4

iTrader: (96)

This ain't no SBC.......well it is, but not a Gen I. You plan on doing some before and after flow tests to see how much you improved them?

k_cash1432

iTrader: (9)

no just trying to get a lil more flow i know these heads flow way better than most aftermarket sbc heads but mostly just to smooth runners up and let it flow smooth. what about what dodson55 uis talking about? I admit to not searching much before starting this thread but i have never heard that before, I thought the LS1 intake valves were bigger than the valves on the 5.3.

01ssreda4

iTrader: (96)

LS1 valves are bigger.

k_cash1432

iTrader: (9)

Yes thats what i thought he ment but wasnt for sure. Should i mill the head to bump compression up? Gonna use my ls6 cam to start out with may go with a bigger cam down the road but that wont be for a while.

dmelvin

iTrader: (8)

You're going to bump compression without milling. LS1 heads have 66cc chambers, the stock 5.3 heads have 61 cc chambers.

01ssreda4

iTrader: (96)

You planning on running premium fuel all the time? Do you have a competent tuner in your area?

BIG_MIKE2005

iTrader: (116)

I'm extremely happy with my stock cast 5.3 heads. I had Bo White do a port/polish job on them & milled them .018" to get me around 11:1. He also swapped the stock intake valve for the bigger stock intake valve from the 241 (car)heads. Then cut the valves for better flow at lower lift since I wanted to run the 224/224 .581/.581 cam. Sent them off to Gunnar@ patriot to install the spring kit & flow them. They did well with 261 @ .500 lift on the intake side/219 @ .600 lift on the exhaust side. That was on par with a set of Patriot Stage II's at the time.

PREDATOR-Z

They will have to be ported right and intake valve changed to at least 2.00
On LS heads it is not just a matter of hoggin' them out. One has to take just the right amount in the right places.

k_cash1432

iTrader: (9)

So im going to deffinatly do dome more research on porting my heads before i hit the coolant passage by the exhaust valve. ssred Didnt thik about running premium fuel in it all the time closest i have is 25 miles but then i can get some c10, or whatever aviation fuel is. IS their a calculator that i can use to figur out compression ratio? or atleast the formula to figure it out.

k_cash1432

iTrader: (9)

Just a couple last questions for ya guys.
What head gasket do i use? The LS1 gasket or the 5.3 gasket? Im assuming i can use the LS1 gasket so it wil cover the whole bore but just would like some reassurance.

ARP head bolts are not reusable, correct?

batboy

iTrader: (6)

You want to use LS1 head gaskets. GM bolts are not reusable, but ARP bolts can be reused. CR will be raised about 3/4 of a point.

k_cash1432

iTrader: (9)

OK thanks for the answer I was pretty sure i could use the LS1 gasket but wanted a second opinion. with the 5.3 heads bumping up the compression up 3/4 of a point what will that put me up to? 11.0, 11.1-1?

Here is the link I used to figure its rough but it will get me close.

https://ls1tech.com/forums/advanced-...ume-vs-cr.html