Black6SpdTA

Can someone explain lift flow figures to me? Do you want better high lift flow or low lift flow? Intake or Exhaust? If head A flows better than head B (Intake) but head B flows better than head A (exhaust), which head would you want?
-Rippin

NTChrist

Depends on the engine combo a lot.
Post some specs of the engine you have/are building, and the specs of the heads you are considering.

Heads, like carbs, can flow too well.
Velocity is needed for properly filling the chambers, and creating the exhaust scavenging effect.

You want better high lift flow if you are using a high-lift cam, with steep ramp angles. Something like a big roller cam.

You want low lift flow if you are concerned about torque, and are using a low-lift, low ramp angle cam.

There is a general rule of thumb that concerns intake versus exhaust valve flow. You want the exhaust to flow somewhere around ~70ish% of the intake valve's capacity.
Too much exhaust flow, and you've got a forced induction head. Too little exhaust flow, and you're choking the engine.

K?

Black6SpdTA

I'm not building a motor, I'm broke. I'm just planning for next year. The motor will be an L98. I initially looked at the Vortecs (w/ spring upgrade). Then flipped the page and saw the L98 Corvette Bowl Job heads. The heads flow as follows:
I/E

Vortecs (64cc):
0.100"-70/48
0.200"-139/101
0.300"-190/129
0.400"-227/140
0.500"-239/147

L98 Bowl Jobs (58cc):
0.100"-56/50
0.200"-117/96
0.300"-164/130
0.400"-199/148
0.500"-220/161

Both are 1.94" x 1.50". It seems the L98 BJ's flow better on the exhaust side slightly but the Vortecs flow much better on the intake side.

Anyone know what numbers I could expect with an L98, StealthRam, Shorties, around a .500 - .525" lift cam and both with the Vortecs and L98 BJ's?
-Rippin

NTChrist

I would go with the Vortec's.

If you are using a .5" lift cam, keep in mind that the cam is only at 0.5" lift for about 2 degrees of the lobe. The rest of the time, it's somewhere between that, and zero. This means that you should focus on the mid-lift numbers. Doesn't matter if the L98 exhaust moves 14 more cfm @ 0.5" lift, you won't see much of that lift anyways.

There are other things to consider when comparing these 2 heads also. The Vortec has a much better combustion chamber, and will make more power, even if the flow numbers are the same.

Are the 58cc L98's milled f-body heads (64cc's stock), or are they the Vette heads?

I don't think anybody could accurately guess what kind of power your engine is going to make. Especially if you don't provide details like lift duration.

Black6SpdTA

I am pretty sure the L98's are the Vette heads. I'm going with the Vortecs, a pair for $640 vs. $1300 (L98's). I'm not looking for an accurate number, just a ballpark figure. I haven't had time to look at cams yet but when I do, I'll post the specs.
-Rippin