Hey guys, I asked this question in another type of forum and they told me to come here to ask.

I have an 86 LB9 305ci with ported and polished iron heads with about 5000 miles on them...

I bought L98 aluminum vette heads from this guy who said they have 15000 miles on them... they are polished but NOT ported...

EDIT: they are from a 1990 corvette.. which have the "D" shaped exhaust ports which supposedly flow better..

Which ones should I keep?

Thanks,
-Marc

 

The iron heads will probably make a hair more power at this point.
Since this is on the 305, the iron heads will keep your CR higher, and the port job will make them flow more.

 

Both heads should have the same CR... both are listed at 58cc chambers.

 

the heads are 58cc for sure, that I know.. I'll be using a GM head gasket (if that makes any difference?) and I will be cleaning them before install.. But I wanna know if I should port them... Perhaps I should but would it be worth it or should I just sell them and keep the iron ported ones I have on there now?? (i bought these because they are 50lbs lighter.. which I thought would be better! I also thought they would flow better..)

Anybody elses opinion?
Thanks guys!
-marc

 

Aluminum heads are like running lower compression though. The reason why the the vette l98 had 58cc aluminum and fbody had 64cc iron. Has to do with heat retention, etc.

 

I know - I just wanted to clarify that the mechanical compression ratio would be the same, as the two heads have the same size chambers.

The L98 aluminum heads aren't anything particularly special in stock form, but they do have potential. I haven't dealt with a set of those heads specifically, but I do recall hearing from people that have that they have fairly meaty ports, so there is lots of room for port work. They also already have screw-in rocker studs and angled plugs, which is a plus.

If you do some homework on what those heads really need as far as port work goes, they would be a great budget performance head. I almost used a set myself, untill I found a set of 200cc World heads for a VERY good price... But anyway, they Vette heads would probably be worth it if you do some work with the ports first.

The GM "L98 Corvette" head gasket is .028" compressed, incase you didn't know.

 

Thanks guys, I'll check out my heads first, and if the port job on them makes them flow better than these vette heads then I'll sell these vette heads.

I appreciate the help!
take care,
-Marc

 

Only way to know for sure is to have them bench tested

Just because the ports are all smooth and shiny, doesn't necessarily mean they flow any better.