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Hi guys,
Based on the following rule of thumb:
"there are rules of thumb for figurin' out intake runner volume. Cubic inches times 0.50 for a good running street motor and cubic inches times 0.55 for a max effort motor."
What kind of cylinder heads would your recommend for a smaller displacement street SBC (i.e. 283, 302, 305, 307)?
Seems like most aftermarket heads would flow too much for these displacements.
Thoughts?
12558060 L31 Vortec on all but the 305. The bore is too small and will shroud the valves. I've been able to make some pretty incredible power on the Dynosim with Vortecs on a 283/292/302 using a solid flat tappet cam. You have to use a lot of cam in these small motors and rev the snot out of 'em anyway, so by the time you use a 3000 stall converter, you're moving some pretty serious air and the heads are just right from that point to redline.
That's good to know re: the 305. I didn't realize what a small bore it had until you mentioned it. What would you recommend for the 305 in this instance?
Further, which aluminum head would you recommend for the 283, 302, 307, 327 crowd?
Cheers,
J
'97 Chevy truck used Vortec cast iron heads, GM P/N 12558059 with the smaller valves (1.84"/1.5").
Remember the Vortec heads require a different intake manifold.
Chevy High Performance did a 305 build up with these heads and an Xtreme Energy cam, Edelbrock Performer and a 750 carb and got somewhere around 325HP. As I recall, they also used Xtreme Energy valve springs and maybe some porting/polishing (very slight). You may still be able to find the article.
I don't think you can get to much head ether! To answer his question How moch head you use depends on how high you want the power band to be . Even a 302 needs a good flowing set of heads at 9000 RPM.
For a street engine without RPMs going past 5500-6000.
OK, here's a nice little 375hp 283 street motor with hydraulic cam that would work well with a stock converter.
Assuming that is would be possible to cut the L31 decks for 60 cc's (about 0.028") without making a cracking problem, you could make 9.15:1 static compression ratio with flat-top 6cc pistons and a 0.035" squish. I remember reading years ago when these heads came out that it was not recommended to use a domed piston with them to raise static c.r. I wouldn't do it anyway because in my opinion, the dome gets in the way of flame propogation across the chamber.
283 bored 0.060" with flat-top, KB165 6cc pistons. Cut block decks to 9.015" for 0.010" piston deck height. Victor Reinz 5746 head gaskets, 4.100" bore, 0.025" compressed thickness for squish of 0.035". L31 heads with stock 1.94"/1.50" valves. Cut head decks 0.028"-0.030" for 60cc chambers, 9.15:1 static compression ratio. (598 cylinder, 60 head, 5.4 gasket, 2 deck, 6 piston).
1 3/4" long-tube, equal-length headers, RPM Vortec intake, 600 carb.
Compcams part number 12-230-2, grind number XE250H, 250/260, 206/212, 0.432"/0.444", installed 2 degrees retarded at 108/112/110.
RPM HP TQ
1500 85 300
2000 123 323
2500 158 332
3000 202 353
3500 249 374
4000 292 384
4500 329 384
5000 362 380
5500 374 358
6000 375 328
6500 354 286
Tech not with that Camshaft . Maybe with an EX262H and a Well set up 650 Carb .
I was thinking XE262 with a Vortec Performer EPS Manifold. Otherwise, I am totally onside with everything else suggested. Good advice. Much appreciated.
Think the Performer RPM would be a better bet?
With the XE262H the Performer RPM would be better . But with the XE250H the EPS is Better .