I lined my fully p&p'd 195cc AFR LT4 heads up next to the p&p's LS6 heads my friend owns. Comparison analysis: one wouldn't doubt looking at the intake runners that both sets of heads have about the same potential. However, the LS6 has a substantially larger (volume) exhaust port - probably where they get a good portion of their power over LT1/LT4 heads.

Here's my question, I hope someone knows the answer: can I port the AFR's out to match the exhaust gasket w/o hitting water or leaving the aluminum walls too thin? I have to believe that, if I could do this, I could make some pretty substantial gains. I'd call AFR directly (and I may anyway), but the chances that I'd get someone competent/knowledgeable on the phone are probably pretty small . . .

 

Why bother comparing a 23 degree head to a 15 degree head? It just doesn't make sense to me.

 

Maybe 15 degree heads are comparable to 23 heads, maybe their not. Which is better really isn't my question. I know that more volume means more airflow potential. I'm interested in knowing how much volume I can get out of my AFR castings and, assuming I can get substantially more, whether I could expect to flow an exhaust side comparable to an LS1/LS6.

 

bigger is not always better. volume is good if the head keeps good velocity. if it doesnt your heads will get turbulent.

 

you wouldnt want to port the exhaust opening larger than the header opening.

 

Is it possible to port the exhaust opening bigger than the header opening? I mean you can always get bigger headers.

But seriously, you'd probably hit water or end up making the casting too thin if you went too big.

 

The LS6 heads can flow monster numbers and make great power. LS1 heads are what make LS1s, plain and simple. Like people said you have to know what your doing, it cant be all about flow numbers, there have been said heads that flowed great but ran like absolute and complete ***. I like the fact we can sun SBC heads on our motors.

 

the fuel injectors do have a clearer shot to the valve on the LS motors and would run cooler down the center because the exhaust ports are not right next to each other

 

www.ws6transam.org/afrheads.htm take a look at this site, he has the basic same heads as you and does some work to them that youre thinkin gof doing.

 

Thanks all. It is appreciated.

 

I feel for ya guy. This is the ? you asked, in your first post: can I port the AFR's out to match the exhaust gasket w/o hitting water or leaving the aluminum walls too thin?

Not one direct answer. One even answered with a ?. Is it possible to port the exhaust opening bigger than the header opening?

I'd state that matching the opening (at the flange) to the gasket, will not be your limiting factor. It is what you do between the port flange and the valve seat, you need to be concerned with. Short of cutting up a casting, or deliberately porting to breakout, I know of no one that knows their cores (or the ins and out of them) better than AFR. Give em a try. What ya got to loose? Be brave, ask for an engineer?