Need Info on Hand Porting LS-6 heads
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Joined: Jan 2008
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From: Carthage,TX
Need Info on Hand Porting LS-6 heads I have a set of LS-6 243 castings i bought for a steal. Before i put them on my Z i want to improve them as much as i can before i put them on,i have machine shop experience and have ported standard small block heads but never an LS style so i i figured id ask before diving into it. Please list any links or pics that are helpful. Thanks
Clean up the bowl area and blend everywhere...short side nice and even radius. I like to open up sides of combustion chamber to match bore and unshroud the valves. Valve stem area and port match to intake.
the most important thing to do is get a GOOD valve job,with proper blending into the bowls..without that your gains in airflow won't be worth the effort in working the rest of the port..the rocker bolt boss is not really much of a restriction until you start moving a lot of air..
with just a proper valve job and bowl blend you can get over 280cfm..
with just a proper valve job and bowl blend you can get over 280cfm..
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Joined: Mar 2004
Posts: 14,620
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From: BFE
A professional valve job is the main importance.
I picked up 50 hp going from 2.06's to 2.19's in my BB 496. but not without running a fly cutter down the pocket and blending to 87% relief into pocket.
And that was with full exhaust.
And that was with full exhaust.
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A lot of mention of a "good" valve job, but no specifics. Stock is 2 angle, seat and sligh throat cut. Perhaps a cut below the throat cut to further blend the VJ into the port?
One thing I noted on mine, the seat (steel part) overhangs the casting. So for sure would want to blend that into the casting. Would be nice to have a cutter that would do that and the seat all n one fell swoop....I imagine one exists. I also imagine the seat material is very hard.
I have read that the short turn is tricky. Easier to screw up than improve.
I have noted also on photos of the CNC jobs by AI etc, they don't seem to follow the 85% rule....but then I haven't had those heads in my hands.
Sadly, the AFR205's I have are on my C5......not going to remove them to have a look. Although I had them apart and took a bunch of photos.
I want to do the same as the OP. And I have similar experience.
Ron
One thing I noted on mine, the seat (steel part) overhangs the casting. So for sure would want to blend that into the casting. Would be nice to have a cutter that would do that and the seat all n one fell swoop....I imagine one exists. I also imagine the seat material is very hard.
I have read that the short turn is tricky. Easier to screw up than improve.
I have noted also on photos of the CNC jobs by AI etc, they don't seem to follow the 85% rule....but then I haven't had those heads in my hands.
Sadly, the AFR205's I have are on my C5......not going to remove them to have a look. Although I had them apart and took a bunch of photos.
I want to do the same as the OP. And I have similar experience.
Ron
A lot of mention of a "good" valve job, but no specifics. Stock is 2 angle, seat and sligh throat cut. Perhaps a cut below the throat cut to further blend the VJ into the port?
One thing I noted on mine, the seat (steel part) overhangs the casting. So for sure would want to blend that into the casting. Would be nice to have a cutter that would do that and the seat all n one fell swoop....I imagine one exists. I also imagine the seat material is very hard.
I have read that the short turn is tricky. Easier to screw up than improve.
I have noted also on photos of the CNC jobs by AI etc, they don't seem to follow the 85% rule....but then I haven't had those heads in my hands.
Sadly, the AFR205's I have are on my C5......not going to remove them to have a look. Although I had them apart and took a bunch of photos.
I want to do the same as the OP. And I have similar experience.
Ron
One thing I noted on mine, the seat (steel part) overhangs the casting. So for sure would want to blend that into the casting. Would be nice to have a cutter that would do that and the seat all n one fell swoop....I imagine one exists. I also imagine the seat material is very hard.
I have read that the short turn is tricky. Easier to screw up than improve.
I have noted also on photos of the CNC jobs by AI etc, they don't seem to follow the 85% rule....but then I haven't had those heads in my hands.
Sadly, the AFR205's I have are on my C5......not going to remove them to have a look. Although I had them apart and took a bunch of photos.
I want to do the same as the OP. And I have similar experience.
Ron
Speaking of the throat, I'm more inclined to believe the throat % is a maximum. There are formulas out there to ball park how big you want the minimum cross section in the port based off of displacement and where you want torque to peak. According to this formula, 2.6sq in was the throat area that I needed to put peak torque where I wanted it, and it was coincidentally 90% of the valve. The big *** valves that I'm putting in my 243 heads are going to keep the same throat area, but it will drop that percentage down a lot since it's a much larger valve.
BTW, I like big valves. The bigger the better, even on LS heads!
