So I'm looking at this 70k LT1 motor. It is from an ImpSS and I was wondering if the heads are worth messing having a mild port job done to them. I want to build an LT1 motor and price is a steal. I've read the steal heads breathe better than the aluminum heads and have bigger combustion chambers. The only downfall is they aren't aluminum so the heat dissapation isn't as good. But i'm looking for educated advice. Are they decent heads?

Or should I buy a used set of aluminum heads?

 

The irons seem to crack if ported too heavily. The heat transfer everyone loves about the aluminums is really wasted energy as any heat that is used to do anything but expand gasses and drive the piston is wasted.

The iron heads flow better than most of the aluminums AS CAST and the most desirable aluminums for porting are the early low flowing ones. The later aluminums that equal the iron flow are thin and considered less desirable for porting than the early heads.,

Only way I see the big chamber being a benifit is for forced induction.

They are not bad heads but if your performance goals are serious the early aluminums ported by a good shop are the best bet.

 

Thanks Dwayne, how much porting can these suckers take before cracking occurs, and yes I was thinking of Forced induction.

 

I really don't know and I suspect a BIG part of it is exactly where the porting is done.