Performance of early vs. late 8V N/A heads
11-20-2011, 10:52 AM
#1
Rennlist Member
Thread Starter
Performance of early vs. late 8V N/A heads
In the 944 Spec world, there has been some debate about the performance potential of the various heads put on the 8V 944 over its production. I was interested if anyone has an objective data on the 6R. vs 7R, vs. 8R heads.
I'd be especially interested to know if anyone has put these on a flow bench.
The 6R head appears to a have a more machined combustion chamber, with sharper edges, and appears to have a bit more valve shrouding. Some have claimed the port volumes are less. The 8R head a combustion chamber that appears more cast, with softer edges, and the appearance of less valve shrouding.
Pics are below
6R:
8R:
Thoughts?
I'd be especially interested to know if anyone has put these on a flow bench.
The 6R head appears to a have a more machined combustion chamber, with sharper edges, and appears to have a bit more valve shrouding. Some have claimed the port volumes are less. The 8R head a combustion chamber that appears more cast, with softer edges, and the appearance of less valve shrouding.
Pics are below
6R:
8R:
Thoughts?
Last edited by Sterling Doc; 11-20-2011 at 04:55 PM.
11-20-2011, 11:22 AM
#2
Nordschleife Master
Porsche didn't publish any increase in hp on any of the 944na 8v, except for the 88/89 models and that was due to higher compression pistons in the last two years of production. If a head design change increased performance I am sure they would have published this.
I can only assume that the different head designs were manufacturing improvements or even a change in manufacturer, a very common occurrence over the years of production.
I can only assume that the different head designs were manufacturing improvements or even a change in manufacturer, a very common occurrence over the years of production.
11-20-2011, 04:53 PM
#4
Rennlist Member
Thread Starter
Porsche didn't publish any increase in hp on any of the 944na 8v, except for the 88/89 models and that was due to higher compression pistons in the last two years of production. If a head design change increased performance I am sure they would have published this.
I can only assume that the different head designs were manufacturing improvements or even a change in manufacturer, a very common occurrence over the years of production.
I can only assume that the different head designs were manufacturing improvements or even a change in manufacturer, a very common occurrence over the years of production.
11-22-2011, 09:41 PM
#5
Race Director
Lindsey emailed me back and unfortunately said they have not compared the N/A heads in any great detail. They do not accept the early head with divot in the side of the intake runners as cores and stated they rarely see that style.
From Mike: "The other difference I have seen is there are 2 different combustion volumes. 55cc
and 57cc. My port man has made comments on the NA head how the port design is
inferior to the turbo head, its the position of the valve seat in relationship to the port.
All of the castings vary to some degree, but he said overall the NA head will never flow
what a turbo head will no matter what you do to them.
I think I have a head that has already been CC'd, I will see what number it is. It is a 57
cc which is the one we see the most. The 55cc head is the rare one."
From Mike: "The other difference I have seen is there are 2 different combustion volumes. 55cc
and 57cc. My port man has made comments on the NA head how the port design is
inferior to the turbo head, its the position of the valve seat in relationship to the port.
All of the castings vary to some degree, but he said overall the NA head will never flow
what a turbo head will no matter what you do to them.
I think I have a head that has already been CC'd, I will see what number it is. It is a 57
cc which is the one we see the most. The 55cc head is the rare one."
