Before I start talking the first thing I want to say is that I have never ported heads before and I'm using this thread to hopefully get some good advice and learn what I can while messing with this set of heads. I know some about head porting, but just enough to be stupid on the subject lol.

I'm taking a class right now where we are going over head porting and using the flow bench but I know different head designs and port shapes require different techniques for good gains. My teacher knows a lot about older engines and head designs but he is kind of new to the LS stuff so I decided to come here for some pointers

First things first, I have a set of 243 casting LS6 heads that I'm going to be working with. I put them on the flow bench and here were the results(stock, untouched ports with stock valves):

(@28" H2O)

Intake
.100 53.31CFM
.200 118.52CFM
.300 182.92CFM
.350 206.76CFM
.400 226.13CFM
.450 239.54CFM
.500 250.71CFM
.550 253.73CFM
.600 236.56CFM
.650 239.54CFM

Exhaust
.100 34.12CFM
.200 95.45CFM
.300 125.89CFM
.350 146.64CFM
.400 156.00CFM
.450 162.24CFM
.500 168.48CFM
.550 172.38CFM
.600 176.28CFM
.650 178.62CFM

These results were the highest flowing ports on the heads but all ports were within 1-2 cfm.

I'm not really shooting to get the highest gains possible out of these heads. Again, this is just a learning experience for me and I think it will be good to show everyone what I did and how it changed flow so you can see what to, or what not to do, at my expense lol I'm going to start porting Monday(ish) so if anyone has any legitimate advice they would like to throw in I'll be more than happy to take it and use it the best I can.

 

cool, save those heads for later. get some other castings... 241 853s whatever for 30-50$ and mess with them.

 

Agree'n with studdern, find some cheap ls1 heads and work those over first. It would be sad to see some nice ls6 heads go to waste if you make a mistake or have an accident. If you search around the site, you can find some good pics of some already ported cathedral heads for reference. That way you can see where the most material should be taken from and what spots to leave alone. Remember, just because the #'s might end up really high, that doesnt mean the head will perform amazing by any means. Its all about how well the air can move through the ports, not how much space is available for airflow. Good luck with the porting and let us know how it goes.

 

do what they said.if you do a search you should be able to find some good pics of DIY ported ls heads.take your time on the first couple of ports .

 

I have a set of 241 heads that I'm going to play with first. I also have a set of sbc heads but I kinda wanted to mess with the cathedral port design and learn off of that for now.

I'll trying doing some more searching and see if I can find some pics. If anyone has a link by all means please post it up lol

 

I have a set of bare 806s from my 98 that I will give you for free to play with if you just cover shipping. They are seriously just sitting my my garage as giant aluminum paper weights.

 

243 castings are so nice that it doesn't take much to exceed the flow
capabilities of a stock ls1 or ls6 intake (approx 250 & 265 cfm). With
that being said, as others have stated a bigger hole may have big
peak cfm but port speed and fuel atomization is what makes torque.
In short the most mid lift enhancement with minimal volume increase.
I've only tweaked 1 set of 241s with moderate improvement for about
4hrs total investment. A good valve job with backcuts on the valves
will help. Many suggest removing the rocker boss bump in the In. roof.
(use sealant on the rocker bolt as a small hole is iminent). Also blend
the bowls with a cartridge roll (80 grit) definitely don't want smooth
or polished finish on the In side. Boundary layer dropout = bad thing.
Lastly try to acheive 75-80% Ex. to In. ratio for a balanced cylinder
head. 85% loves NOS. good luck

 

Cool, take lots of pictures!

 

Thanks for the advice. I'm not shooting to get 290cfm out of these things or anything, just trying to get some sort of gains as a learning experience for my class

also, on the exhaust ports, is it best to leave those with a slightly rough finish opposed to polishing the crap out of them?

 

I used the same 80 grit rolls cuz thats what I had but other than cosmetic
appearance the exhaust side just takes on carbon anyways.

 

I just got done porting one intake and one exhaust port on my LS6 heads. I'm going to have it flow bench hopefully sunday or monday. I'm going to compare a mild home port job vs the next cylinder ports being stock. I will have a dirrect side by side flow results. I'll have pics also of the ports.

 

My goals are to have more cfm in all if not most lifts above .200, and possibly hit 270cfm at .550 lift(with the cam i'm going to be running)

 

Generally the exhaust ports get enlargened , smoothed and polished . True they will build alot of carbon but rough will build carbon a little quicker than smooth and exhaust gases will scavenge more completely being larger than stock and smooth .

 

So did you ever get the numbers after you ported the heads?

 

Best bet for the money, install larger valves, have a machine shop "bowl hog" them and blend it in.

 

Pay attention to the sound the ports make as you are flowing them, a good port will sound completly different than a bad port.
Take your time to try to get them all the same, what happens with most first time porters is you start to get tired and things just start to get sloppy.
Take breaks as you go and you will do better.
I also try to get one area in all the ports roughed in and then move on to another area, that keeps you from having to move the head around as much. That may not seem like a big deal at first but it can make a real difference whan you are porting somthing like a big block head.

Andy

 

also a good valve job is needed to help reach some good flow numbers.

 

interested in the results as well
Kory

 

How well does the bowl hog work on the ls heads? I was under the impression that it was for older style heads...

 

Not sure, the most flow potential is in the bowl area.