zacht

iTrader: (18)

anyone have numbers with aftermarket heads that have been ported? or any comparisons? most i see on here are bone stock aftermarket heads.

also. any size engine! i want to see some.

AINT SKEERED

iTrader: (2)

Very few people buy after market heads and have them ported.
They usually are Cnc ported already to flow very well.

zacht

iTrader: (18)

true. i know they are very well flowing head in their "stock" form (guess you'd call it that) just wondering if anyone has any numbers or input on if they have tried to improve any aftermarket heads.


also-i see lots of great aftermarket heads that flow 320-350 cfm on the intake side, which is awesome! seems size/airflow rules are different with ls motors, which i know, just wondering things about some of these huge LS7 and huge aftermarket heads that flow insane numbers... but what about guys putting them on smaller CI motors (not LS7 heads) but heads that flow insane numbers like them...

guess im saying-

427 LS7---heads flow 380-400 cfm

402-418...(ls1..LQ...LS3...under 4.070 bore) mostly have heads that flow 330cfm...

which in relation to another are completely different, but seems like numbers are down for the smaller ci guys compared to the bigger hitters...

ss454327

iTrader: (10)

Well there is a lot more to making power than flow numbers. If the engine doesn't need the volume of air a head can flow what use is it. Also huge flowing heads could reduce air velocity and actually LOSE hp compared to a lesser flowing head. I don't even understand all of it but there is a happy medium between flow and velocity.

AINT SKEERED

iTrader: (2)

Main reason is because big flowing heads have big ports which lose air speed. Small motors need airspeed to get all the Tq and throttle response they can.
4-4.070" bore motors can work with ls3 heads but the valves are shrouded on the smaller of those bores.
Cams stay smaller as well and let the big port do the work to make the power.

zacht

iTrader: (18)

i understand that bigger isn't always better. and bigger ports kill velocity. im trying to figure out the magic with those LS7 heads having 260-280cc runners and flowing damn near 400cfm...they're making huge power with a smaller cam...

just seems like smaller cube motors (402-418...even the LS3 427 4.070 bore) are running some wild combinations to get to 550rwhp, while the LS7 with its masive heads and 4.125 bore is doing 550rw pretty easily.

im seeing if anyone has improved an already good set of heads (afr 225, tfs 235...etc.) on any combination under 4.07 bore...increasing veloctiy and flow...

im not trying to jump out here saying 'bigger is better, i want more' seeing if anyone has done work on their aftermarket heads, and what results they got (good or bad)

gnx7

iTrader: (28)

Running ported LS7 heads and out of the box TFS235's on a 427-440ci motor on my buddy's setup shows that the LS7 heads make more power from about 6500rpm and higher. But at everywhere lower in the powerband the TFS heads make more HP and 20-30 ft/lbs more torque. Everywhere.

Depends where you want the power. Also LS7 heads have titanium valves which are nearly $1K by themselves. They are entirely different heads. They need a 4.125" bore also as you know.

LS3 heads out of the box flow nearly 330cfm and are a good bang for the buck.... but a TFS/AFR head will make more power but will cost more.

If you need that last couple percent HP/MPH from your combo then it is worth having ANY head further finessed.

Cubes make HP the easy way.

zacht

iTrader: (18)

Ok! That's a good comparison there.

Next question then...where does the tsp 227 and 237s rate against the afr/tfs 235s (or about that size. I know they have a little less flow but price wise can't beat them when running stock rockers with trunion upgrade. Prc heads are cheaper and don't require aftermarket rockers...

SpinsB

iTrader: (5)

lots of good info here guys.

redtan

iTrader: (5)

You can't really compare LS7 wheel numbers to others unless they are in the same car.

An LS7 in a vette will lose less hp through the drivetrain than a 416 motor in an f-body. That's why you see stock cubed LS7s put down nice numbers while wild strokers don't. It's mainly because of the more efficient corvette drivetrain.

Also, the fact that you're comparing strokers with 4.070 bore vs. LS7s with 4.125 bore makes a difference, that extra bore really helps out the bigger LS3/7 heads.

zacht

iTrader: (18)

ok i agree with you...

just making the comparison as to why---427ci with 4.125 bore has heads flowing 380-400+(ported) vs... say 402..408...418...even 427..428 (4.07 bore or less) have heads flowing 340 or less cfm at .600. i know bore affects flow of the head and the same head on different bores flows way different numbers.

mostly im trying to see exactly how good some aftermarket heads are compared to others. just seems like 550rw in a LS7 is pretty normal. but someone with a 400in LSx hits 550 and its an awesome setup. hype maybe?

spicebird98

iTrader: (10)

No head is at its full potential unless after the CNC'ing it gets some "massaging" by hand IMO