LS1_MK2_Supra

Stock for stock what head is better or worse and why? I have been searching the forums but it seems that most people port them. I have a set of stock 5.3 heads (06 Tahoe) and a set of stock LS1 heads (98 Vette). I read somewhere that they have the same flow numbers stock but the 5.3 heads will bump the compression. My questions....
How much will they raise the compression?
Which flow better?
If you had both, and no money to port them, which would you use?

My plan for this motor is to toss it in the Tahoe, cam, headers, tune, done.

Thanks for any input.

Isolde

iTrader: (4)

What are the casting numbers?

hammertime

iTrader: (1)

1) 98 LS1 heads should have a perimeter bolt pattern

2) what engine are you building a 5.3 or a 5.7?

3) what do you hope to do with the truck when its done (driver, tow vehicle, etc)

Flow differences between the heads should marginal, with a slight edge going to the later heads due to changes in the casting methods.

Compression differences will be the biggest thing. LS1 heads have 67cc chambers compared to 61cc for 5.3's. A 5.3 with LS1 heads will drop the compression below 9:1 and lose power. A 5.7 with 5.3 heads will push the compression over 11:1, probably not the best scenario for a heavy truck, especially if you might still tow anything.

LS1_MK2_Supra

The head casting number on the LS1 heads is 806 and they are perimeter bolt. I am building the LS1 to take some weight off the front of the truck. The Tahoe is a Z56 PPV that I am not going to be doing much towing with if any at all. I plan on making it a quick and fun to drive DD, that may see the track a few times.
Thanks again for your input.

LS1_MK2_Supra

I once saw a chart that listed all of the casting numbers for the heads and the differences, anyone know where that is?

5_02ls1

iTrader: (20)

www.smokemup.com


do the 5.3 heads.....flow is damn near the same even with the smaller intake valve....and you get slose to a point in cr....the higher cr is what you want in a heavier vehicle...it makes for better tourqe....

hammertime

iTrader: (1)

A 5.7 with some extra compression and mild cam sounds like the hot ticket. The 5.3 heads will do you well.

Good luck with your build.

LS1_MK2_Supra

I did some math, the heads should bump the compession to 10.8:1
With a mild cam, tune, and headers I hope to make some power.

HitmanLS1

iTrader: (16)

http://www.theturboforums.com/smf/in...=122987.0;wap2

This may help you.

JohnFrazee02SS

iTrader: (23)

Hitman that was some awesome info

Killer66

iTrader: (4)

Question? How much of a horsepower increase will I get If I swapped 4.8 piston heads into my 5.3 LM7? The 4.8s are flat and the 5.3 dished!
Thanks in advance

LS1_MK2_Supra

They are not the same bore. That would not work.

dodson55

iTrader: (18)

They are the same bore and the same pin height so they will work as far as power gains I really do not know if I had to guess i would say 10-15 hp

Fry_

what casting # are the 5.3 heads some '05 and late 5.3's came with 243's or 799's

A.R. Shale Targa

iTrader: (2)

This is true however you would have to pay a competant machine shop like
4 dollars per to remove all 8 pistons, a few bucks each to hone the pin bores
and another 4 x 8 to reinstall on the 5.3 (6.098") rods. I'd guess around 100
dollars total not to mention the pistons will weigh different by as much as 20
grams and this could throw the crank out of balance.