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CamaroAJ
12-12-2006, 01:00 PM
i can get a brand new set of GMPP 18° heads and intake for a pretty good price. i know a rocker set will set me back another $1300 and longer valves and push rods but is it worth it or is there a reason this guy has been stuck with them for 3 years? i tried to do a search on here but don't really come up with anything. anyone have any advise?

68sixspeed
12-12-2006, 04:18 PM
Make sure they are the newer raise runner ones, most are; there were some early heads with lower runners that did not make as much hp. Also remember you are going to need 18 degree relieved pistons and custom headers, although I think Headman has an 18 degree camaro header. I wouldn't bother with these unless you are going to use enough cam to make them work right. (no litttle hyraulics for these, think .700 lift mech roller!) -Dan

ScotI
12-12-2006, 05:21 PM
I've read that to benefit from the 18° heads on the GEN I sbc, you gotta have pretty decent compression & a fairly large/agressive cam.

Is it because the runners are so large they hurt velocity?

The GEN III based 15° heads get away w/mild cam/compression ratios & offer better low speed drivability..... it would be nice if you could get similar benefits from the early sbc stuff.

68sixspeed
12-12-2006, 06:20 PM
Most 18 degree runners start at 238cc and go 260-280+ ported, which does raise the power band up in rpm. They can be made to make good power on lower compression-- look at the Busch car motors that are 9:1 by the rules. The large valves the 15-18 degree sbc heads also makes for some large bowl area, once again raising the power band. Also keep in mind most Nascar origin heads are for 4.125" bore; even though those motors are 358cid, they destroke 4.125" bores to get to that cubic inch. If you haven't done a short block yet, 377cid with 18 degree heads is a great winding motor.

CamaroAJ
12-12-2006, 07:41 PM
no i don't have anything yet thats why i was thinking about them. 377 sounds pretty good, i was going to build twin turbos but might put that off and just go with a 10.5:1 engine that will wind up pretty high. the car will be mostly street driven but will see quite a bit of autocross.

Lowend
12-13-2006, 12:24 PM
I'm not a huge fan of 18 deg heads... they really don't start to work until 3000+ RPM and this isn't a good option for most street or Auto-x cars
If you plan on revving to less than 7500 I would take a pass