Head help. Please!!!!!!
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Staging Lane
Joined: Sep 2012
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From: Stringer ms
I need some help. I have a 6.0 iron stock compression. I have 241 heads or a set of 317 heads milled 30 thousandths. Which ones should I run?
Forgot this is going in a 99 Camaro with 4l80 trams.
Forgot this is going in a 99 Camaro with 4l80 trams.
What camshaft are you going to use?
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http://www.gmhightechperformance.com...d/viewall.html
"The question of the day seems to involve the difference between the original cathedral-port and modern rectangular-port LS heads. More specifically, which one is better? Were we to compare two sets of production heads, there would be little comparison, as even the very best production (cathedral-port) LS6 heads (243 castings) offer nowhere near the flow and power potential of the current LS3 heads. Based on flow numbers alone, the LS3 head has the LS6 heads covered by 50-60 cfm on the intake side (though the change in chamber volume will drop the static compression ratio). The flow figures alone make the swap over to the LS3 components very desirable, especially considering the fact that the stock LS3 head will support well over 600 horsepower (we recently made 690 hp on a 468 stroker with stock LS3 heads). The downside is that the head swap from LS1/LS6 heads to LS3 heads is more involved than a simple R&R. The new heads require a 4.00-inch bore block, LS3 rockers and intake manifold as well, both increasing the cost and limiting the swap potential to 6.0-6.2L motors (and big-bore stroker variants)."
"The results of the head-to-head shootout indicate that (despite the flow differences) the cathedral-port heads were the equal of the rectangular-port LS3 heads. It is interesting to note that the cathedral-port heads offered better low-speed power and produced peak torque lower than the LS3 heads (irrespective of cam choice)."
"The question of the day seems to involve the difference between the original cathedral-port and modern rectangular-port LS heads. More specifically, which one is better? Were we to compare two sets of production heads, there would be little comparison, as even the very best production (cathedral-port) LS6 heads (243 castings) offer nowhere near the flow and power potential of the current LS3 heads. Based on flow numbers alone, the LS3 head has the LS6 heads covered by 50-60 cfm on the intake side (though the change in chamber volume will drop the static compression ratio). The flow figures alone make the swap over to the LS3 components very desirable, especially considering the fact that the stock LS3 head will support well over 600 horsepower (we recently made 690 hp on a 468 stroker with stock LS3 heads). The downside is that the head swap from LS1/LS6 heads to LS3 heads is more involved than a simple R&R. The new heads require a 4.00-inch bore block, LS3 rockers and intake manifold as well, both increasing the cost and limiting the swap potential to 6.0-6.2L motors (and big-bore stroker variants)."
"The results of the head-to-head shootout indicate that (despite the flow differences) the cathedral-port heads were the equal of the rectangular-port LS3 heads. It is interesting to note that the cathedral-port heads offered better low-speed power and produced peak torque lower than the LS3 heads (irrespective of cam choice)."
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From what I have learned doing a fair amount of reading, as a GENERAL rule of thumb...
Rectangular port heads tend to always do better at high RPMs because of their superior flow numbers. On smaller displacements, namely below approx 400 CI, this will come at the expense of low end torque.
As your displacement goes up, above 400 ci and 4" dia, you are better off with rectangular port heads. Low end torque will not suffer much or at all.
If you are below 4" diameter, you can't use rectangular/LS3 heads. Cathedral port heads tend to make more low end torque on smaller displacements and do almost as well at high RPM.
If you have an engine with a displacement right at the margins, 400 CI/4"dia, then it's really just a judgement call.
And as mentioned early, cam choice and goals play a large role. If you're going for a peaky cam in a dyno queen, get the rectangular, for sure.
I'm not an expert on heads, just did my own research for my own build. If I'm wrong about any of this, hopefully one of the real builders here will chime in and correct me.
http://www.carcraft.com/techarticles...s/viewall.html
Also, from a pure cost effectiveness standpoint, GMPP or CNC rectangular port heads tend to be a better value for the money. GM is able to produce them more cheaply due to changes in their manufacturing process.
Rectangular port heads tend to always do better at high RPMs because of their superior flow numbers. On smaller displacements, namely below approx 400 CI, this will come at the expense of low end torque.
As your displacement goes up, above 400 ci and 4" dia, you are better off with rectangular port heads. Low end torque will not suffer much or at all.
If you are below 4" diameter, you can't use rectangular/LS3 heads. Cathedral port heads tend to make more low end torque on smaller displacements and do almost as well at high RPM.
If you have an engine with a displacement right at the margins, 400 CI/4"dia, then it's really just a judgement call.
And as mentioned early, cam choice and goals play a large role. If you're going for a peaky cam in a dyno queen, get the rectangular, for sure.
I'm not an expert on heads, just did my own research for my own build. If I'm wrong about any of this, hopefully one of the real builders here will chime in and correct me.
http://www.carcraft.com/techarticles...s/viewall.html
Also, from a pure cost effectiveness standpoint, GMPP or CNC rectangular port heads tend to be a better value for the money. GM is able to produce them more cheaply due to changes in their manufacturing process.
Last edited by Capricio; Oct 5, 2012 at 09:44 PM. Reason: link
