4.8 lsa head swap test
TECH Resident
Joined: Sep 2013
Posts: 994
Likes: 120
From: Mechanicsburg, PA
Give him a break guys. He's got a little one, wife, head cold and a job.
Now get that Fairmont out and get to work Matt, hah! I vote for a 30-40 psi boost threshold on e85 with water/meth. On a stud/gasket/cam only engine this time. And twins would be nice, since it's not my money or time I'm spending.
Now get that Fairmont out and get to work Matt, hah! I vote for a 30-40 psi boost threshold on e85 with water/meth. On a stud/gasket/cam only engine this time. And twins would be nice, since it's not my money or time I'm spending.
Give him a break guys. He's got a little one, wife, head cold and a job.
Now get that Fairmont out and get to work Matt, hah! I vote for a 30-40 psi boost threshold on e85 with water/meth. On a stud/gasket/cam only engine this time. And twins would be nice, since it's not my money or time I'm spending.
Now get that Fairmont out and get to work Matt, hah! I vote for a 30-40 psi boost threshold on e85 with water/meth. On a stud/gasket/cam only engine this time. And twins would be nice, since it's not my money or time I'm spending.
hey im a Matt fan no doubt, but why portray something that isn’t valid? Of course it picked up power with the lesser heads, it gained compression and non leaking valves. What else would you expect. But what’s intriguing is the leaking heads made more power where they did, imagine if they wouldn’t have been leaking. He was probably losing 60+HP from leaking Valves.
Restricted User
Joined: Mar 2014
Posts: 7,192
Likes: 109
From: Ohio
Its a relevant test either way.
Don't look at it as a swap from 799 to 862s as a 60 horsepower gain.
Look at it as a reminder that you should still take a quick look over your junkyard parts because something small could be costing you a ton of power.
I actually went out and check the valves on both my 317s and 799s after this and ordered some valve lapping compound.
Don't look at it as a swap from 799 to 862s as a 60 horsepower gain.
Look at it as a reminder that you should still take a quick look over your junkyard parts because something small could be costing you a ton of power.
I actually went out and check the valves on both my 317s and 799s after this and ordered some valve lapping compound.
Its a relevant test either way.
Don't look at it as a swap from 799 to 862s as a 60 horsepower gain.
Look at it as a reminder that you should still take a quick look over your junkyard parts because something small could be costing you a ton of power.
I actually went out and check the valves on both my 317s and 799s after this and ordered some valve lapping compound.
Don't look at it as a swap from 799 to 862s as a 60 horsepower gain.
Look at it as a reminder that you should still take a quick look over your junkyard parts because something small could be costing you a ton of power.
I actually went out and check the valves on both my 317s and 799s after this and ordered some valve lapping compound.
Great vid...
With a blowers fixed flow dependent on RPM I can see the smaller chamber always being beneficial. When you're limited to the amount of boost you can run more compression will always perform better if you're fuel is good enough to hold off detonation. I bet he could have milled and filled those heads up to 11-12:1 on E85. Would have been cheap easy power.
With no boost limit in place, say with a turbo... I feel like the 799s would still outshine the 862's assuming you had enough turbo to take advantage of the additional flow. That said I just sold a set of 799's for $550 and picked up some 706's for $40! Price VS performance on the small chamber is pretty hard to argue under 1000hp where the majority of the hobby guys are. Anything over that I agree with the aftermarket head suggestion.
With a blowers fixed flow dependent on RPM I can see the smaller chamber always being beneficial. When you're limited to the amount of boost you can run more compression will always perform better if you're fuel is good enough to hold off detonation. I bet he could have milled and filled those heads up to 11-12:1 on E85. Would have been cheap easy power.
With no boost limit in place, say with a turbo... I feel like the 799s would still outshine the 862's assuming you had enough turbo to take advantage of the additional flow. That said I just sold a set of 799's for $550 and picked up some 706's for $40! Price VS performance on the small chamber is pretty hard to argue under 1000hp where the majority of the hobby guys are. Anything over that I agree with the aftermarket head suggestion.
Staging Lane
Joined: Dec 2016
Posts: 82
Likes: 3
According to richard holdener he did a dyno tests with the 706, 241, 317, and 799 stock heads on a 5.3l. The 706 make more power throughout the curve than the others. The 799 had about 2 peak hp less than the 706.. They were the closest. Even though the 706's flowed the least cfm's they made the most power.
Than he did the same test under boost with the same comparible results. The key is matching the heads to bore size. So from what i gather that even if the valves were fine on those 799's it still probably would lag behind those 862's on that small of motor.
Than he did the same test under boost with the same comparible results. The key is matching the heads to bore size. So from what i gather that even if the valves were fine on those 799's it still probably would lag behind those 862's on that small of motor.
Last edited by Stonerracing; Jan 16, 2019 at 03:54 PM.
According to richard holdener he did a dyno tests with the 706, 241, 317, and 799 stock heads on a 5.3l. The 706 make more power throughout the curve than the others. The 799 had about 2 peak hp less than the 706.. They were the closest. Even though the 706's flowed the least cfm's they made the most power.
Than he did the same test under boost with the same comparible results. The key is matching the heads to bore size. So from what i gather that even if the valves were fine on those 799's it still probably would lag behind those 862's on that small of motor.
Than he did the same test under boost with the same comparible results. The key is matching the heads to bore size. So from what i gather that even if the valves were fine on those 799's it still probably would lag behind those 862's on that small of motor.
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