Batass

Are there any heads that will outperform swirl port heads under 4500 rpms?

kdrolt

That's an unusual question here (counter to the usual SP head questions).

A small port aftermarket aluminum head might, like 180 cc AFR heads for sbc, but they're aluminum and $$$ so the mild gain at rpm below 4500 wouldn't be worth the cost. Ported swirl port would also (duh) be an improvement because they will flow better than stock while retaining the swirl and the fast burn that goes with it.

If you read Fast355 posts on the SP heads he has ported for his van and for his brother's 'burban, I think you'll find that he has had very good luck with them both below and above 4500 rpm.

I'll also add that a long time ago (a few years), Fast355 was a critic of SP heads because, like many people, he had no real experience with them other than stock and running through a stock engine - - - so he would repeat the hearsay found in typical TBI TGO posts. Then he started porting them, and his opinion changed completely. So his experiences with them are more valuable because he once also thought they were junk. HTH.

Batass

Right, that wouldn't be worth the cost. I have heard that vortecs only increase the power after about 4000 rpms. From what I have read, the vortec head does the same thing that the swirl ports do, but with a 170cc runner instead of the SP's 185. Must not be quite as efficient though under 4000 rpms or the vortec would make more tq due to the smaller port. The vortecs swirl the air in the chamber, letting the port flow better at higher rpms. This motor will never go above 5000 rpms.

It is a very unusual question. I'll take a look at fast's posts.

Fast355

iTrader: (2)

Here is a picture of Dyno Don's porting on his 193s. Mine is very similar. Do not grind out the swirl ramp, merely trim it and work on the bowl.

Batass

Do you have any dyno numbers?

yort

I had been reading up on the old swirl port head porting threads… I just dropped off my heads at the shop for a valve job and cleanup… when I get them back I’ll take a stab at porting them. From what I can tell… most of the work just smoothing things out, correct?