4.8 lsa head swap test
4.8 lsa head swap test I did a head swap from what most people would consider a really good cyl head, the stock 799's as they had exhaust valve seat pitting, wich is fairly common, to some dirty old 862 heads from 2002 4.8 i had laying around.
dropped them on and picked up almost 40whp up top. funny considering the intake valve is smaller, but the head chamber is also smaller
it raised my compression from 8.8:1 to 9.53:1
it was an interesting experiment to see if it would be a push or worth it.
food for thought a hellcat makes 640whp on my dyno
dropped them on and picked up almost 40whp up top. funny considering the intake valve is smaller, but the head chamber is also smaller
it raised my compression from 8.8:1 to 9.53:1
it was an interesting experiment to see if it would be a push or worth it.
food for thought a hellcat makes 640whp on my dyno
TECH Fanatic
Joined: Sep 2013
Posts: 1,011
Likes: 129
From: Mechanicsburg, PA
Not busting your chops. I really appreciate what you have done for the automotive community. But that test isn't very accurate. The"good" heads had leaking valves. And you said it makes another 1-2psi of boost as a result of the changes. But we always appreciate the honest data anyhow!
That said I too went from 317's to 862's on the same setup and picked up a few MPH on the same boost, but was still 5-6MPH down from the aftermarket heads.
That car turned out really nice Matt! You should run it at a half mile or mile race, perfect for it! I ran my bike at the Texas Mile last year and while the turbo blew up and took a dump and never got a good result it was a lot of fun and very laid back.
Have you driven this combo on the street yet? I am curious to see if you have an issue with lean tip in as some have reported.
Also, Was it actually pitting on the valve seats or cracked in between the seats?
Also, Was it actually pitting on the valve seats or cracked in between the seats?
Last edited by 1FastBrick; Jan 15, 2019 at 01:18 PM.
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I went and watched your youtube video on this... I'm shocked that the 862 heads actually made slightly less down low, but made a lot more up top. Can someone explain how this happened? Maybe the 799's with issues actually are what caused them not to perform as well up top? Not a criticism at all as no one is really doing these type of comparisons, but I'm seriously interested in learning.
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On The Tree
Joined: Dec 2013
Posts: 182
Likes: 11
From: North Vanacouver , BC
At relatively low power or a setup that's not maxed out I agree 100%, under 1000hp on most setups you can easily turn up the boost and save the money. But when you're already at 35+psi on the largest S400 offered and you are looking for a few more MPH aftermarket heads are a viable option if you don't want to completely rework the turbo kit or build another engine. You can take that 1200 hp or so limit of stock heads chucking gaskets and bump it up to 1400hp or more keeping the heads down. Between a turbo upgrade to S500 or GT55, bigger engine, or better flowing heads in some cases a set of TFS heads is the cheapest option and we did see them perform, easily picked up MPH on less boost.
That said I too went from 317's to 862's on the same setup and picked up a few MPH on the same boost, but was still 5-6MPH down from the aftermarket heads.
That said I too went from 317's to 862's on the same setup and picked up a few MPH on the same boost, but was still 5-6MPH down from the aftermarket heads.
Lol what about the part where he said he could see daylight between the valve and valve seat?
edit. This video. Fast forward to 1:16
edit. This video. Fast forward to 1:16
Last edited by Kfxguy; Jan 16, 2019 at 12:11 PM.
