99reddevilFRC

What do i need to do to a stock set to be performance enhancement over a my stock heads on my 99 ls 1?

jermzz

iTrader: (18)

You'll get higher compression with 5.3 heads compared to ls1 heads, which will increase midrange power, but other then this your question make absolutely no sense.

jalper

iTrader: (9)

do you mean like a port and polish or what you should replace the heads to.

jermzz

iTrader: (18)

I'd just get a machined set from one of the sponsors....... you get what you pay for. If you pay some jenky machine shop for a port and polish be prepared for not that much of a performance gain.

PREDATOR-Z

You'll need to fully CNC port them and change valves.

99reddevilFRC

I have a free set just wondering if it was worth fooling with if you cut them down, ported them, you would still need to replace the valves?

Jason 98 TA

iTrader: (4)

We offer complete cnc porting & competition cnc valve job with milling & reassembly for $750. You can add larger valves for right at $200 & your ready to roll with a nice set of heads!!

99reddevilFRC

Thanks for helping. How much is normally milled to acquire 11.0 CR? Do they flow right with ls1heads stock for stock?

PREDATOR-Z

Stock for stock, No, they flow less than LS1.
To acquire 11:1 you need around 61>62cc

99reddevilFRC

Thanks for all help. Anyone know how much the heads need to be cut down to acquire 11:1 CR? .020? .030?

Canbarelygo

i actually heard 5.3 heads stock even with the smaller valves flow within a few cfm from .100 all the way to .600 as stock ls1 heads so id think adding bigger valves to 5.3 heads would put you at right around the same flow with more compression. thats what i did anyway i had to take the heads off my car and i found a cheap set of 5.3s and the shop said they would sell em to me, transfer all my valves, springs, etc. to the 5.3 heads and surface them for like 350 including buying the heads. i do believe the runners are them same size so i would think the only thing keeping the 5.3 heads from flowin what ls1 heads do could be the valves.

Nick V.

iTrader: (1)

ive got some 5.3 heads in my dads truck that arent going anywhere.... i wonder if i could do anything with them....