I may have a chance to pick up some L98 corvette heads for free. They'd need to be rebuilt though. I've got 461 fuelie heads on my car right now. I've got a TPI 355 with 10:1 flat top pistons. How will the 58cc combustion chamber work with the flat top pistons? Won't this give me something over 11:1 compression? Is that do-able on pump gas with aluminum heads?

Secondly, is it worth it? Are these going to significantly outflow the 461s? What I've heard about the 461s is that they have good high rpm flow, but have an inefficient combustion chamber design that promotes detonation. I've also heard that their flow inhibits low end torque, which would of course be a hinderance on a TPI car. What do you guys think?

 

If you're at 10:1 now with 64cc heads then the 58cc chambers will bump you up to about 10.6.

They probably flow about the same but will save 50lbs off the front of the car due to the aluminum construction. Get them ported, however, and they'll outflow your current heads by a good margin.

 

Jim, I can't help with a direct comparison between the heads, but what you've heard about the 461's...maybe is confused with the 461x's with the larger intake ports? Or maybe after the 461's have been ported?

The 461's were good head for the horodders of old, not so much as a bolt-on-and-run, but they were able to work them over to support a lot of power.

I'd never heard that they had a poor combustion chamber design, I always thought it was a good design...being that there was no spark plug protusion casted into the combustion chamber.

Maybe pumping up this post will get RB involved

 

Go to the site in my sig, and check out the mag articles. There is a CHP head flow comparo test there, I think it has the 461s flowed against the Al L98 heads. As I recall the L98s actually flowed less on the intake side...

EDIT, oops, looks like it 462s they tested, along with 882s and 441s. Page 4 has the chart with those and the L98s. Maybe it'll help give you an idea anyway...

 

the 461's will flow much better then the heads your looking at, the only stock head that outflows the camel hump heads are the vortec's

 

The 461s were some of the oldest of the "fuelie" heads... they lack the "squish" area that was added to the later ones and in fact are therefore highly prone to detonation. Also, they lack the accessory bolt holes in the ends, so they are difficult to install in one of these chassis, unless of course you can do without a couple of modern conveniences.... like an alternator. I can't imagine how you've got one on your car now but it will be a much better setup (restored to stock) with the other heads.

As far as raw flow numbers, the newer Vette casting has similar flow potential to them; and since it's aluminum the higher compression is probably acceptable.

One down side to the L98 heads is the lack of an EGR passage. You would have to be the judge of whether that's a problem for you. I'd think you'd be better off with it, at that high compression.

Still, I believe that I would use the L98 heads if I was in your situation. If fyou have good valves or other hardware on your 461s you could move it all over to the others. Use the Fel-Pro 1044 gasket to reduce the compression a little bit.

With a TPI on there, I don't think the difference in flow would make a significant difference.