LS2 question
Here is a Hot Rod magazine test where they ran stock 317 cathedral ports vs stock 821 rectangle ports vs a AFR 245 head. The 821 rectangle ports made 38 more horsepower and 17 more ft pounds of torque than the 317 cathedral port heads. And, I bet if you put a really good valve job on the 821 rectangle ports, they would make the same numbers or better than the AFR 245s:
http://www.hotrod.com/how-to/engine/...re-port-heads/
http://www.hotrod.com/how-to/engine/...re-port-heads/
11 Second Club
Joined: Sep 2011
Posts: 390
Likes: 2
From: The Burnie, MD
Show me a case of just heads changed and things being that similar?
I already posted the HotRod article where they actually tested 317s and LS3s back to back yes the shortblock was larger but was consistent, do you think that overlay trumps back to back testing? No exhaust/header, cam, CAI etc. influence.
Even when they test more similarly sized aftermarket heads in each style they see a torque difference and the extra airflow not turning into the power one would expect.
http://www.superchevy.com/how-to/ght...-head-to-head/
I already posted the HotRod article where they actually tested 317s and LS3s back to back yes the shortblock was larger but was consistent, do you think that overlay trumps back to back testing? No exhaust/header, cam, CAI etc. influence.
Even when they test more similarly sized aftermarket heads in each style they see a torque difference and the extra airflow not turning into the power one would expect.
http://www.superchevy.com/how-to/ght...-head-to-head/
My plot is a stock LS2 with stock LS3 heads and intake. The other is stock 243's with a FAST 102. Same displacement. Again, I can't confirm mchicia1's supporting mods, but anyone who is going to go through a cam and intake swap is probably going to at least have long tubes and an intake.
A lot of truth there. Most of the people I hang out with could give a damn about what goes on below 4000 RPM. They are after average power between 5500-7000+. Really if you think about it, even in a combo with a really tight street converter, the shift drop is about 5200 RPM at the lowest. So, the only time people are below 4000 is leaving from a dead stop when traction is a problem on the street anyway.
With the new cam though I'm reaching the point where power in that area is starting to get excessive and tire spin is more likely. So in the future if more power needs to happen it might be beneficial to lose a little from that part of the curve in favor of more top end HP.
I think I would also rather invest in the LS3 top end over buying a Fast 102 or similar for cathedrals if I needed an upgrade in that department over my Fast 90.
TECH Fanatic
Joined: Jul 2007
Posts: 1,802
Likes: 333
From: Wilmington, De
The 4L60E was essentially around for 20+ years at that point, and every other manufacturer was offering their vehicles with 5 and 6 speed transmissions. So, GM needed to make a change to stay competitive, especially with the Corvette and Cadillac segments.
This is why the 06 and 07 Corvettes came with 6 speed automatics despite having the 243-headed LS2, and the 07-08 Silverado Vortec Max was offered with the L76 and 4L60E. It had nothing to do with lowend responses and everything to do with staying relevant.
Here is a Hot Rod magazine test where they ran stock 317 cathedral ports vs stock 821 rectangle ports vs a AFR 245 head. The 821 rectangle ports made 38 more horsepower and 17 more ft pounds of torque than the 317 cathedral port heads. And, I bet if you put a really good valve job on the 821 rectangle ports, they would make the same numbers or better than the AFR 245s:
http://www.hotrod.com/how-to/engine/...re-port-heads/
http://www.hotrod.com/how-to/engine/...re-port-heads/
You said yourself that both heads need different cams to make the most of them, so you're never going to get an apples to apples comparison doing a back to back head swap. Right?
My plot is a stock LS2 with stock LS3 heads and intake. The other is stock 243's with a FAST 102. Same displacement. Again, I can't confirm mchicia1's supporting mods, but anyone who is going to go through a cam and intake swap is probably going to at least have long tubes and an intake.
My plot is a stock LS2 with stock LS3 heads and intake. The other is stock 243's with a FAST 102. Same displacement. Again, I can't confirm mchicia1's supporting mods, but anyone who is going to go through a cam and intake swap is probably going to at least have long tubes and an intake.
The link I posted and speedtigger thinks he found is rectangle cam same motor and exhaust and all with just the heads and intake swapped, and the 317s are known to have the same ports as 243s so it is a reasonable comparison. Beyond that I think everyone will agree the 243s would have some advantage over 317s.
It was not that I was ignoring the performance below 4000 RPM as much as it was that I just don't care. I know guys with tow trucks and luxury cars might care, but I don't.
On the street, pretty much no one is gonna be able to notice the 5% power advantage of the 317 heads. And on the track, that 5% power advantage will disappear with the first gear shift.
Again.....just my opinion.
KW
Last edited by KW Baraka; Dec 31, 2015 at 12:05 AM.
Remember like a month ago when you said my Caprice had a lot more gear in it than my SS, and I had to point out to you that 4.03/3.27 is actually more gear than 3.06/4.10, so how much thought have you put into it. How objective are you if you can't identify something so blatantly obvious when owning both vehicles yourself so long?......
And all the bluster in the world on your part won't make it true (SMDH).
And I'd bet that my full weight '96 SS would make a more comfortable daily driver than your car as well.
Jus' sayin'
......KW
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