Porting question on head
01-26-2008, 02:01 PM
#1
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Porting question on head Ok guys I want to swap out the 241 heads with the 243 zo6 heads asap but First I want to port the 243 heads for more h/p. See my signature for the mods done to my car. I know the difference between the two heads on the intake/exhaust port cc's( 241 intake port volume :200 cc/ exhaust port volume : 70 cc)(243: intake port volume : 210cc/exhaust port volume : 75 cc), the valve sizes are same on the two heads(intake valve 2.00"/exhaust valve 1.55") but what is the combustion chamber size on 243 ?. The 243 heads had 3 angle valve job, dual manley coil spring capable of .650 lift 1500 miles ago posted by the guy i boughtthe head from . So can i reuse the existing springs,valves, & all the hardwares with my current set up ? if so do i have to change anything so i don't run into problem w/my current mods ? Lastly, what spec should i port the 243 heads to to get the maxium h/p out of them ? but not too extreme of a port
job because i still want to keep the streetability .
job because i still want to keep the streetability .
01-26-2008, 03:53 PM
#2
Most of your power is gonna come from the area around the valve, so thats where you are gonna want to focus your efforts. Send the 243's out for a good valvejob, but there are a few things to consider before you do.
First, the stock valves can't really handle a "race" valvejob. The stock valvejob isn't cut with the seat all the way out to the 2.00" diameter of the valve. I think it's more like 1.95" or so. This is for longevity. If the seat is cut all the way out to a 2.00" diameter, the valves have a tendency to collapse in, or "tulip".
The next thing to consider is if you go with bigger valves, the actual seat insert diameter may be too small. You can do a 2.02" intake, but the valvejob won't turn out properly and negates the positive effects of a bigger valve/valvejob. So it's almost pointless unless you install bigger OD seat inserts. Then you can go 2.06", 2.08", or whatever.
From there, you can now "port" the heads. Main focus should be on narrowing the guides, removing the bump under the rocker bolt hole (it's okay to break through to the threads), and blending everything in while removing as little material as possible. In the chamber, just knock off all the casting roughness and open it up to a 4.030" bore to match the cylinder.
Here's what a NICE LS6 chamber looks like:
It's up to you and your budget as to what you can do, but I hope that helps a bit.
Good luck with the project.
First, the stock valves can't really handle a "race" valvejob. The stock valvejob isn't cut with the seat all the way out to the 2.00" diameter of the valve. I think it's more like 1.95" or so. This is for longevity. If the seat is cut all the way out to a 2.00" diameter, the valves have a tendency to collapse in, or "tulip".
The next thing to consider is if you go with bigger valves, the actual seat insert diameter may be too small. You can do a 2.02" intake, but the valvejob won't turn out properly and negates the positive effects of a bigger valve/valvejob. So it's almost pointless unless you install bigger OD seat inserts. Then you can go 2.06", 2.08", or whatever.
From there, you can now "port" the heads. Main focus should be on narrowing the guides, removing the bump under the rocker bolt hole (it's okay to break through to the threads), and blending everything in while removing as little material as possible. In the chamber, just knock off all the casting roughness and open it up to a 4.030" bore to match the cylinder.
Here's what a NICE LS6 chamber looks like:
It's up to you and your budget as to what you can do, but I hope that helps a bit.
Good luck with the project.
