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I bet you would see some improvement by going to a 2 inch intake and blending the valve job into the bowl.
Most likely, but I am going to punt. I'm going to swap the converter next. It was doing weird stuff on the dyno when i locked it. On the street I notice it shuddering a little bit when it locks up sometimes. If no improvement, I'll change the cam and heads. I have a really nice set of 799s touched up by AI just sitting in my spare bedroom.
The more I look at flow numbers of factory cylinder heads in stock form... I think I F'd up using those 862s. Too much hype on the Internet saying they are they the best thing since sliced bread. My experience with them has been lackluster. I am not a fan and would not do it again.
On the cams, if my math is right:
TSP CHOPacabra = +2 overlap
my old EPS = -7 overlap
The Sloppy best = +1 overlap
Going from -7 to +2 overlsp, despite the roughly 1 point in static compression increase explains some of the TQ loss. I mentioned the "best cam" because I have one and am most likely going to pair it with those AI 799s. My only other cam option is a Summit 218/227 .600"/.600", which is -1.5 overlap.
I am still going to change the tq converter and go back to the dyno to see if that was part of the issue. Kind of a give it one last chance. But, I'm pretty much dead set on swapping the heads and cam for something different.
Last edited by Bluecollar Hotrods; Dec 28, 2022 at 09:09 PM.
The more I look at flow numbers of factory cylinder heads in stock form... I think I F'd up using those 862s. Too much hype on the Internet saying they are they the best thing since sliced bread. My experience with them has been lackluster. I am not a fan and would not do it again.
I have a contact at Cam Motion when i order cam for a setup. I tell them all the specs and they grind a cam and ship it. They have all the cool stuff to know the details. Havent been dissapointed yet.
The more I look at flow numbers of factory cylinder heads in stock form... I think I F'd up using those 862s. Too much hype on the Internet saying they are they the best thing since sliced bread. My experience with them has been lackluster. I am not a fan and would not do it again.
On the cams, if my math is right:
TSP CHOPacabra = +2 overlap
my old EPS = -7 overlap
The Sloppy best = -1 overlap
Going from -7 to +2 overlsp, despite the roughly 1 point in static compression increase explains some of the TQ loss. I mentioned the "best cam" because I have one and am most likely going to pair it with those AI 799s. My only other cam option is a Summit 218/227 .600"/.600", which is -1.5 overlap.
I am still going to change the tq converter and go back to the dyno to see if that was part of the issue. Kind of a give it one last chance. But, I'm pretty much dead set on swapping the heads and cam for something different.
so again, the compression bump helped your case in having more overlap with the new cam... the power difference is in the cam's happy powerband vs the heads' happy powerband. a top-end cam ain't gonna be so hot with low-to-mid RPM heads.
if you've already got some worked 799s, then i'd say mill a few thousandths off, get new pushrods, and let it eat.
What version of AI heads do you have?
What cam are you looking at?
What's your Plan/ Goal for this engine?
Performance rebuild, no porting. Good valve job, milled to 63cc, BTR duals and Ti retainers. I have a brand new Summit stg 2 truck cam in stock. (High lift version) From what I understand, it's a revised hot cam with .600" lift.
Goals? Make decent power, maintain some drivability. My truck is 4600lbs and some change w/o driver, 4.10s, will have a converter and supporting mods. 336rwhp just isn't going to cut it, I'd like to be around 375-380
As promised, changed the converter last weekend - went back to the dyno today. And... absolutely ZERO gain. Kind of what I expected. We made a few changes trying to squeeze more out, but it has no more to give.
So my thoughts, I would never do stock 706/862 heads on a 6.0L again. I don't care what the engine dyno on the Internet says, real world experience... hard pass.
Now, just need to figure out when I can do the heads and cam swap + retune next month. I'd also like to make a few passes with this set up first. I'm going to guess mid 13s, maybe it will surprise me.
Blue lines are current, red is previous with the factory converter.
Last edited by Bluecollar Hotrods; Jun 25, 2023 at 11:24 AM.
Dec 27, 2022 | 05:33 PM
