zgeezer Posted November 6, 2002 Share Posted November 6, 2002 Does anyone have any information comparing the lt1 iron and aluminum heads for performance potential. Several Lt1 Impala sites state that the iron (vortec design-straight plug) out flow the aluminum lt1 ('92 Corvette, F body, excluding Lt4) by a substantial amount. My knee jerk is that the aluminum lt1 must be a better performance head. After all they put them on Corvettes..... right? Any help is welcome. I've both and should decide soon. The cam is a ZZ3 roller out of an early aluminum headed chevy crate engine: the smog legal 350 replacement for middle 80s Camaros. gw Quote Link to comment Share on other sites More sharing options...
Mike C Posted November 6, 2002 Share Posted November 6, 2002 I have heard the rumor as well. I can't say specifically, but I will offer this for thought. Two friends did work on their Impala SS. One low mileage '96 swapped on AFR LT1 aluminum heads (which are SUPPOSED to be better than the GM Al heads) and ASM (Arizona Speed and Marine) coated headers with a Borla exhaust. It dynoed 267 hp at the wheels. The other car was a high mileage '94. He pocket ported the iron heads and added a custom comp cam (the one I was asking about last week)270/284 advertised 215/224 @ .050 .500/.500 lift with 1.5 rockers. This car had stock manifolds and cat back Flowmaster exhaust. It dynoed at 293 hp at the wheels! Same day, same dyno. The work was all done by another friend to take the mechanic out of the picture. First guy spent over $2200 + labor. Second guy spent $500 + labor and made WAY more power! If you want to see where to spend your money, obviously it is with the cam. Best bang for the buck IMO is the LT4 Hot Cam kit and pocket port the iron heads. Three reasons to go aluminum, in order of importance in a Z (IMO of course), (1) weight,(2) tolerance for higher compression, and (3) repairability after an accident. My CNC ported heads off of a '96 SS camaro are testament to that, the supercharged car dropped a valve but the head was repaired which saved the $1500 worth of port work. But pocket porting is cheap and easy compared to the CNC porting which is easy, but surely not cheap! I re-read your post... Unless you are using an electric waterpump then you cannot run the cam for the early ZZ unless you machine it for the cam driven waterpump drive, or if you are planning on running the LT1 heads on an early block, the coolant passages do not align. Quote Link to comment Share on other sites More sharing options...
Guest blue73z Posted November 6, 2002 Share Posted November 6, 2002 Check out this site for flow data. LT1-LT4 Head Flow Comparison Quote Link to comment Share on other sites More sharing options...
zgeezer Posted November 7, 2002 Author Share Posted November 7, 2002 Thanks for the information. The only reason I'm going (considering) the ZZ3 is availablity. It's been taking up space in my garage for about 5 years. I have access to a large lathe, so the machine work is not a problem. However, which ever cam I use must be compatible with the cpu and automatic transmission. It's a '96 so I have on board diagnostics version II to deal with. gw Quote Link to comment Share on other sites More sharing options...
Mudge Posted November 7, 2002 Share Posted November 7, 2002 Read with caution because as you can tell and hopefully already know, no two benches will give the exact same numbers, especially since the operators often dont follow the same procedure as another, and they are not listing the methodology used either (flow bore diameter, atmospheric pressure, etc). The slightly higher flow of the Impy head, but lower compression and less timing your forced to use, do not make it worth it. A quick clean up in the bowl will get better than that, just dont go overboard if you dont have the experience. You can convert to OBD I fairly inexpensively, and programming is cheap. I'm not sure where in CA you are, but if you needed a hand with OBD I stuff I could help you out provided you had Tunercat, or if you are semi nearby, or I know people throughout the state who also have experience tuning. Quote Link to comment Share on other sites More sharing options...
zgeezer Posted November 7, 2002 Author Share Posted November 7, 2002 Thanks for all the input. I'll go with the aluminum heads and dress it out as an LT1'Vette. Slanted plugs require another header, but I like the looks and they do save at least 50# off the front end. This leaves me with another salvage lt1 minus a good crank. Sooo I'm shopping for a rotating assembly.....cheap of course. GW Quote Link to comment Share on other sites More sharing options...
Mudge Posted November 7, 2002 Share Posted November 7, 2002 1997 Aluminum LT1 heads are the same flow approximately as the Impala iron heads. 93 has the most meat on them, so they are the 'best' for all out porting as far as LT1 stock goes. The Impy iron heads weigh more obviously, allow less timing, and are lower comrpression (even with a .026 Impy gasket). The flow difference is about 10cfm, big whuppee 94 LT1-T56 411 SAE-RWHP, ported stock alum heads/cam etc Why the ZZ3 cam? Are you going to actually smog this vehicle? That is a teeny weenie cam Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.