slowlsx

iTrader: (28)

im purchasing a c5 coupe and wanting to do either prc stage 2.5 5.3 heads or their prc ls6 stage 2.5 ls6 head. i will have them both milled to 59cc but my question is what are the difference between the two such as one will make more power up top or the other will have more torque, some people run ls6 heads and some people run the 5.3 heads. i just want to get the bang for the buck.

what do you guys think between the patriot ls6 heads vs PRC ls6 stage 2.5 heads?

i tried to do a search but could not find anything so if someone has a link i would appreciate it!

Boosted One

iTrader: (6)

Don't know for sure, but I would be willing to bet they are the same exact port. So the only difference would be that the ls6 heads will be milled to achieve the combustion chamber size. The shape of the combustion chamber would be the only very minor difference I could think of between the 2.

vettenuts

iTrader: (4)

I remember reading that one of the original reasons for using the 5.3 head was the combustion chamber was small enough to allow modification with a CNC machine. This approach pre-dates aftermarket and the 243 head designs. The 243 is later GM technology. Personally I would favor the 243 head design and be very careful about how much material is hogged out of the ports.

Camaro99SS

iTrader: (4)

5.3 truck heads have a smaller port than the LS6 or even LS1 heads. A ported 5.3 head from Texas Speed has 220cc ports, whereas a stock LS6 head measures in near 215cc. A ported LS6 head will hover ~230cc. The smaller ports of the 5.3 will give more low end and midrange power than the LS6's, but the LS6 will flow alittle better and produce more power mainly at higher rpms . On a N/A heads/cam 5.7 there isn't that big of a difference in terms of all out power though. Both heads when ported well flow over 300cfm. Only when you get into a stroker application will there really be that much difference when the bigger port will better feed the bigger motor.

Jason

fatmat80

im partial to the ls6 heads. still learning about flow data, and characteristics, however on the street is were ive seen a healthy amount of r&d. I have yeet to see a 5.3 headed lsx beat a 243 topped lsx. Also when you look on this site at people who have hit the 500 n/a milestone the heads that were used were TFS, AFR, TEA or CARTEK ported 243s. I have yet to see a 5.3 head get it done. They are a great budget head, but for my money 243 is the better choice.

DSRE

iTrader: (7)

IMHO it not the Casting, Its who is Doing the Porting that Matters, PRC seems pretty good, Personally i'd use the 243 Stage 1, If you got those and hand sanded the SSR with some bowl work you'd have stage 2.5 or better numbers or better without extra cost FWIW

BaddBird

iTrader: (6)

There is more to a stage 2.5 than just hand finishing and bowl work.
Stage 1 has stock sized valves Stage 2.5 has oversized valves.

DSRE

iTrader: (7)

Thats fine, doesn't make much of a diff, nothing wrong with the stock valves IMO

printmanjackson

iTrader: (1)

I would pick 243's milled

tillery

iTrader: (4)

TSP does not do any hand finishing or any bowl work. Or at least not on mine.

DSRE

iTrader: (7)

On Most of the CNC Heads ive touched ive been able to see a significant improvement with some bowl and SSR work, FWIW Most Companies "no one in Specific" Use one CNC porting program and you basically pay for the level of hand finishing work thats done, You'd be amazed how important just a stupid transition from the Bowl-Seat can be or how much the right Valve job can get you

tillery

iTrader: (4)

Thats what I was meaning. The bowl area needed some touch up work on mine. I didnt do much just cleaned up casting flaws. So in the future I can reuse them on a 6.0 and see better gains over the 347 I currently have. Mine are LS6 2.5s with .046 removed from the surface. Running the bigger valves they used before(2006) on the newer program heads. I would go with the PRC LS6 head over the 5.3s. Just dont know the port volume of the newer program.

zacht

iTrader: (18)

what kind of differences when you hand polish some cnc'd heads? i got some used prc stage 1 243's and it looks like some is left on the table, they look good, just in a few spots where the factory cast marks are still in the runners in spots. are these gains worth me pulling the valves and sanding the runners smooth? or just bolt them on and go?

to the OP-get what suites your budget, the 243's seem to run a little more money, but some say win hands down in hp contest. i got 243's so call me partial. but ive seen some 2.5 5.3's put down some good power in combos, up to like 470rwhp is some apps....

disc0monkey

iTrader: (10)

personally the difference between the heads would depend on weight, gear, and cam. if your moving a heavy car/stock gears, and a midrange cam 5.3 heads are it.

zacht if you have them in front of you it is def worth pulling the valves and cleaning up the bowl area. this is a region where the air is in high density and peak velocity. this is a all gain no trade off deal, in my mind is a no brainer.

zacht

iTrader: (18)

ok, i got one more question and ill quit messing slowlsx's thread up.

after polishing these heads should i take them to a machine shop and get each runner flowed again? measured again? i bet home polishing would be +/- 1cfm difference....

also is it a wise idea to try and port match the LS6 intake manifold? cam will be 23x and .620x..114+4

disc0monkey

iTrader: (10)

personally wouldn't even think about going to get the runners flowed. it is what it is even after i do an entire port job, and my cars pick up a good amount after my home ports. you'll be fine your not 'doing' that much. but then, i dont know what your goals are for this car.

zacht

iTrader: (18)

my goal is 440na through an LS6 intake with the prc 1's. im thinking i can get there, the cam pat g spec'd me cant lead me wrong. just wondering, if this would be worth 10hp with port matching the intake, ill do it, if its worth 2...doesnt seem worth doing.

any evidence of what the gains are on cnc'd heads vs. cnc'd and polished?

DSRE

iTrader: (7)

Thats Called Shadows from where the CNC doesn't remove Material and thats no big deal its just not as pretty, the Bowl/seat transition and a Babies *** Smooth Short Turn will pick up on any head, atleast 10hp and a lot more in most cases, Don't hit the valve job where the valve seals or you'll need another valve job afterwards! The Port Match is what you do when you match the Intake ports to the size of the gaskets on the heads and intake manifold, Its more of an old school term as Opening up a Factory Composit intake is pretty much imposible as they are very thin, I don't recomend opening the head port up as its Already Plenty Big enough, Better just leaving that alone LOL, almost too big on most LSX Cathedral heads IMHO