pushinfreight

what is the would be the dissadvantage of going with 5.3l head over sticking with a 5.7l head that give me the same comp ration and intak and exhaust flow numbers? Also, is the injector investment worth it if I am not using nitrous or forced induction?

NiceTry

iTrader: (1)

from what i know (but i'm probably wrong) is that the 5.3 heads give you the compression without having to mill them, or at least as much. if you are staying with stock cubes i'd go 5.3 heads. unless you can afford a set of bad *** ls6 heads.

Jammer

iTrader: (1)

FYI, I have 427 RWHP (A4) with the LS1 name brand heads and mild cam (thinks its 224/224 113 ISA, near 580 lift), my friend has, oddly enough, 427 RWHP (M6)with 5.3 heads (also name brand) and slightly smaller cam (222/224, 113, lift unknown).
What does this mean? You decide.

Y2K2LS1

it means he has a six speed and with a slightly smaller cam he puts the same #s to the wheels

But if everything stays constant, the higher compression 5.3 heads have to be worth something I would have to believe. Just how much i dont know. Am i correct in saying that the combustion chamber in a 5.3 head is smaller so in a 5.7 head you would have to mill the heads a certain amount to achive the same combustion chamber size and possibly distorting the chamber by milling too much and changing the characteristics for which it was designed for? The 5.3 head's chamber is designed for a certain cc while the 5.7 is designed for a few more cc's.

JoSeY

the 5.3L heads have a smaller combustion chamber boosting ur CR while still giving you clearance to run a big cam w/out as much fear of PV clearance issues.

It's only a slight bump in compression and milling a set of 5.7L heads 15tho will give you almost as much compression and you still don't hardly have any PV clearance problems. Only when you go 30 or more milled do you run into bad PV clearance problems w/cams like the X1, G5X2 and so forth.

I am running the X1, with MTI Stage 2 heads milled about 15tho to just clean them up a bit, I still run the stock 7.400 length pushrods and have 10,000 miles on this set up and make well over 420rwhp thru an auto.

If you can get someone who doesn't know what a stock set of 5.3L heads are worth and want to get them ported and put the bigger valves in them then they are the way to go w/the stock cubed motors. But, the DO NOT flow as well as the stock 5.7L heads unless you replace the valves in them w/the bigger 5.7L valves....swapping on a set of stock 5.3L heads will bump compression but you offset that gain w/the smaller valves unless you have had work done on the heads.

Hope this helps.

And ONLY the 6.0L heads have the same D shaped port and valvetrain geometry as the LS6 head. The 4.8, 5.3, and 5.7L heads share the same geometry while the LS6 and 6.0L heads share geometry.

pushinfreight

So basicaly what I am hearing is that if I was to get a set of 5.3L heads from one of the sponsers they are going to flow better and make more HP than the stock 5.7L that are on the car now if I was to change the cam from stock.

JoSeY

if you get a set of say TEA 1.5 5.3L heads and a cam, then you will make more power than if you just stuck a cam in ur car.