grinder11

I'm going to ask a question that some might find pretty unusual. Here goes.....
I have stock LS7 heads, fixed by AHP. I'm happy with their performance. However, as most know, the LS7 exhaust port could use some help. So I, like many, run a large split on duration, with intake at 232°, exhaust is 250°. My question is this:
Has anyone had just the exhaust ports ported? I'm sure a small amount could be gained on the intake side, but it seems the exhaust is most in need of help. As a retired Toolmaker, I realize the time is in the setup. However, CNC machinery has changed a lot of machining protocol. Is this a situation where "as long as the head is in the machine, you may as well do both sides"? Or could you save some money by doing only the exhaust? My end goal is to cut the exhaust duration down to 236°-240°, and maintain high rpm power I have now, but add power 'under the curve'. Is this something anyone has done before, or should I just forget it? I'm not looking to set NHRA records here. Just trying to achieve what I described above. Thanks guys.....

Chris555

Not LS7 specific, but other applications it has always been... Well it is already set up and in the machine so might as well do everything you can while you are there.

There might be more work since the program would have to be edited to only do exhaust and not the intake as well

ramairws6

Back in the day when the LS7 first came out shops were just hand porting the exhaust side. Then came just the CNC program for just the exhaust side. Then they moved on to the intake side. This was back when not a lot was known how to "cam crutch" these heads so to speak.....

grinder11

Anyone else want to add their 2 cents? By all means, chime in......

double06

I think the stock LS7 port is like 86 or 87 cc. I see that most of the redone exhaust ports seem to be coming in the 95cc to 100cc area. I know WCCH uses a 100 cc exhaust port, the Dart, Mast and other heads are around that area. I think the new Katech one is 95 cc. So increasing the port by 10%-15% and assuming it is done correctly seems to be the norm.

ramairws6

Correct and then you need to cam accordingly. That was why such crazy cams in the beginning when nobody really had a clue with what was going on.

grinder11

Doing a different cam, or 'cam accordingly', is what I'm after. When I had AFR CNC ported 225 cathedral ports on a 427 Darton sleeved LS1 block, I ran a 232°/236°@.050" lift, the mid range torque was much stronger than my LS7 headed LS7 block. I'm sure the 250° exhaust duration on my current setup is the main reason. I know the 225 cathedrals' ports were smaller, probably too small, for an LS7, but back then they were the top head on the market. No rectangular port heads available then. What I'm after is being able to dial the exhaust duration back a good 10°, and keep the same top end power I have now by increasing the exhaust port's efficiency. I'm thinking this will increase the mid range considerably, along with making for a more fuel efficient engine. Anyone have thoughts on this?