Hi guys I'm new here. I just wanted to ask, what are the differences between the Corvette Aluminum heads and the F-Body cast iron heads besides the fact that one is aluminum and one is iron? I have an L98 Formula and want to do the swap. I'm keeping all of my emissions equip. What should I watch out for? Will there be need for special fabrication? Can I just get a set of new heads from a GM dealer? If so, what are the part numbers? Thanks.

 

There is no egr crossover in aluminum L98 heads. You'd have to fabricate something on your exhaust. These heads also have smaller combustion chambers (58 vs 64ccs), which will give you higher compression. These heads have screw in studs and use guideplates, so you'll need hardened pushrods unless you take them out. If you're going to get new heads, especially production heads, you should at least have them ported before sticking them on. I doubt there will be much difference between aluminum and iron L98 heads, if any. You do save a good amount of weight, though.

 

The L98 aluminum and iron heads runners are the same. The difference between the two is the angle plugs on the L98 allow for a better combustion due to the angle of the plug. With aluminum heads thought there will be a slight power loss versus iron because the heat dissipates better with aluminum and escapes into other parts of the engine. The iron heads retain the heat, leavin your engine cooler which equals more power.

 

Because they dissapate the heat faster, you can up the compression ratio without running into problems with knock. The higher compression more than makes up for the heat loss...

 

the passenger side head is missing one of the accessory holes, it wasn't a problem for me though.

 

In response to some of the above replies: The vette alum head's gruide plates aren't hardened,unless you have the 87 heads,the newer heads had non harden guide plates and rail rockers. Also the rise in compression and weight savings would more than offset the slight power loss of alum.

 

I have a set of these heads on the shelf waiting for the block work to be done. I did drill and tap the missing hole on the passengers side head. I did not now about the EGR cross over missing.What are my opions? Do I need it? What happens if I just put them on? These heads by the way are about 50lbs lighter. I am concerned about the missing cross over????

 

DOH! The passage is only used for EGR operation. It's NOT a life and death situation. So you wont have EGR... big deal ! lol

 

Corvettes run an external EGR setup that taps into the exhaust manifolds if i am not mistaken.