I'm going to buy some aluminum Corvette heads from somebody I know soon...The heads have already been worked, they have been ported, have hardened seats and bronze guides, etc... I was told the heads flowed 233cfm @ .500 lift. They're off an '87 Vette. I'm just waiting to buy them as soon as I get the rebate on my car. The valve size is stock. They'll go on a 383 with 10.5:1 compression and a SR. I'll probably stuff the Compucam in the closet for the 305 rebuild...I think a cam around 275/280 112 LSA @ .500 lift will be used (roller, haven't decided). Has anyone used these heads and found them to be a restriction? Can they be worked more? Looking for 450 RWHP, or as close as I can get. Is it worth putting money into these or buying new heads? They're a good deal as-is. T-56 and 3.73's will back up the 383. I'll use 24# injectors. Ideas? I've never used 'Vette heads before, and some sources say they only good to 330 HP, others say 420+HP. Thanks -dhirocz



[This message has been edited by dhirocz (edited March 22, 2001).]

 

I would say that they would become a restriction above 330-350 rwhp. With a mild cam, the ZZ4 crate motor makes 355hp/405tq at the crank. This is the combo I am putting together for my L98 and expect about 300 rwhp.

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87 Formula 350 13.94@96.67
98 Z28 1LE 13.15@107.59
1LE Owners Association

 

I put together a 350 engine with ported ZZ4 heads, a ZZ4 cam, ported stock TPI intake, SLP 1 5/8" headers, and various stuff you sig in my mods page, and made 280 HP and 380 TQ at the rear wheels. Now I'm using those heads again with an LT4 HOT cam, TPIS intake and runners, and SLP 1 3/4" headers. It should make more power and get me a 12 second timeslip finally.

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West Coast GM Shootout 2001!
1991 Camaro Z28
5.7L 5-Speed (originally 305)
13.25 @ 107.18 MPH
Southern California
Member: SoCal 3rd Gen F-Bodies
Webmaster: SoCal F-Bodies
-=ICON Motorsports=-

 

You need bigger valves in those heads and porting to match and they can flow over 230 cfm easily...but don't base performance just on flow...there only weak spot is the thin deck....They can suppport well over 400 hp,everybody on here is caught up in AFR's but you don't need them to run 12's or even 11's N/A....Like I said get bigger valves if you can,match every thing up in your intake/exhaust and that motor will run very well...Don't get caught up in what everyone says..

 

Marlon from Car Craft mag said putting bigger valves in these heads only gives you a few more cfm, its more money than its worth. But thats his opinion and I agree.

 

I've heard that they can be CNC ported to provide max flow, enough to run mid-12's. What would the price be to have these ported like that, nd who would I need to talk to? They have already been mildly ported...just trying to determine what I need to do, I've never used these heads before!

 

Depends on the porting. I got great results from mine (in flow anyway - velocity should be great too). They flow with AFR Stage 2 LT1 heads, and I've got a street, not race valve job. The big valves help a bunch at low lift, but can shroud at higher lift. A cheaper compromise is to go to the undercut valves at 2.00/1.55 I think. They supposedly allow you to use the original seats.

 

I have seen a little over 250 cfm @28inches on a fully ported , bigger valved Vette head. Kevin has a good point. It would cost you a lot of money to get that extra 10-15 cfm out of the head..