LS head test...
Thread Starter
Joined: Apr 2006
Posts: 5,605
Likes: 1,150
From: Pittsburgh
Would be cool if the milled the 799 to achieve near the same combustion chamber size and or tighten the quench with a thinner gasket to achieve the same compression ratio.
Put them on an equal playing field and see how they fair
Would also be cool if they test a ported set of 706 castings from a few different vendors to see what kind of bang you get for your buck. Maybe they will do a stage 2???
Put them on an equal playing field and see how they fair
Would also be cool if they test a ported set of 706 castings from a few different vendors to see what kind of bang you get for your buck. Maybe they will do a stage 2???
TECH Resident
Joined: Jul 2007
Posts: 967
Likes: 53
From: Winter Haven FL
The test was as even as possible. Grab some junkyard heads, clean them up, new springs and gaskets and see what happens.
The results shouldn't be a surprise. A NA motor can only hold so much air and all the heads easily supply that amount. With that in mind it becomes predictable that the final rankings are in line with the compression.
I'd be interested in seeing if the bore diameter mismatch would cause any detonation issues. I'd imagine with cheap gas and sharp edges you may get some knocking once the engine gets hot. Not sure how the transition is so I may be over stating the issue though
The results shouldn't be a surprise. A NA motor can only hold so much air and all the heads easily supply that amount. With that in mind it becomes predictable that the final rankings are in line with the compression.
I'd be interested in seeing if the bore diameter mismatch would cause any detonation issues. I'd imagine with cheap gas and sharp edges you may get some knocking once the engine gets hot. Not sure how the transition is so I may be over stating the issue though
I would agree that it was a fair back to back test, However alot of people mill them to bring the compression back around.
So it would be nice to see what happens when you do so. Just as was nice to see a back to back stock for stock comparison. 1 Of the first things I typically hear for others telling someone looking to make some more power on a 5.3L, is to get rid of those junk heads and find some 243/799 heads. They flow more...
It's nice to see actual proof.
And your forgetting the most important part of the nonsense spewed on the internet...
243/799 are the best of the best factory castings....
706 are junk because they will crack... or so alot of people think any way
So it would be nice to see what happens when you do so. Just as was nice to see a back to back stock for stock comparison. 1 Of the first things I typically hear for others telling someone looking to make some more power on a 5.3L, is to get rid of those junk heads and find some 243/799 heads. They flow more...
It's nice to see actual proof.
And your forgetting the most important part of the nonsense spewed on the internet...
243/799 are the best of the best factory castings....
706 are junk because they will crack... or so alot of people think any way
Thread Starter
Joined: Apr 2006
Posts: 5,605
Likes: 1,150
From: Pittsburgh
862 have a better rep than the 706. The 243/799 is still probably the better overall head with the larger valve size on a 3.9 or 4.0 bore. A difference of 2 hp on a 400 hp engine isn't even gonna matter.
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In stock form the 799 head will create more compression therefore better n/a. The 317 will be less compression therefore better for boost
Joined: Jun 2009
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From: go get your shine box tommy
Interesting test and always fun to see fair consistent tests but it just goes to show what works best on the 5.3. Also shows that Chevy knows what they're doing when they match heads to blocks. I would imagine a similar shootout would favor 241/243/799 heads on 5.7 and 6.0 which makes sense that they came like that from the factory.
Thread Starter
Joined: Apr 2006
Posts: 5,605
Likes: 1,150
From: Pittsburgh
TECH Senior Member
Joined: Jun 2016
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From: Central Cal.
It's the package as a whole. Not the individual parts. It only makes 20 more Hp and torque or so more than the previous Gen 3 platforum.
Gen 3 later LM7 or L59 is 295HP/ 315-320ish Ft Lbs of torque.
Gen 4 LY5 or LC9 is 315-320HP /335-340ish Ft lbs of torque
Joined: Jun 2009
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From: go get your shine box tommy