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They are geared more towards the low end.
if you look at the dyno results like when Richard Holdner did the comparison you will see they are restricted on the top end.
The biggest flaw I see is that he didn't compensate for the compression ratio difference. Had he milled the 799/243 heads to get closer to the 862/706 head, I think the difference seen would be much less.
336/343 With a very small cam, basically stock heads, and a stock block, isn’t really that bad in my opinion. I’m assuming it’s through an auto too?
I mean, I’d be tickled to death if my Tahoe made 400rwhp with a much bigger cam, ported 243s, and all the same bolt ons.
Pretty much... unknown mile shortblock straight out of the junkyard. Junkyard cylinder heads, hand-lapped valve job. 4L80E, 4.10 gears, heavier than factory 18" billet wheels. It drives well, and has been reliable. Track testing to come next, then heads and cam swap.
They are geared more towards the low end.
if you look at the dyno results like when Richard Holdner did the comparison you will see they are restricted on the top end.
The biggest flaw I see is that he didn't compensate for the compression ratio difference. Had he milled the 799/243 heads to get closer to the 862/706 head, I think the difference seen would be much less.
He HATES when people say that. So much that I think he's going to actually mill some and redo the test.
I hate having time to dwell on things...
I am seriously thinking that the Summit 8720 might not be enough of a change. I have a custom grind on Comp XER lobes, 224/232. It made killer power in a Gen IV 5.3L - I may go with that cam instead and roll the dice. I want to see a big change if I'm going to do the work.
I hate having time to dwell on things...I am seriously thinking that the Summit 8720 might not be enough of a change. I have a custom grind on Comp XER lobes, 224/232. It made killer power in a Gen IV 5.3L - I may go with that cam instead and roll the dice. I want to see a big change if I'm going to do the work.
Going with a bigger cam with heads that don't flow that spectacular in the higher rpms isn't going to help much. Your going to loose some low end and not gain much on the top end.
Going with a bigger cam with heads that don't flow that spectacular in the higher rpms isn't going to help much. Your going to loose some low end and not gain much on the top end.
I'll be swapping to the Advaced Induction 799 casting heads at the same time as the cam swap, the 862s are not staying.
So bringing this back up since I went to the track Friday night...
looking at my graph has me thinking, peak torque at 4700 RPM with such a small cam and the small valved 862s??? I think it would have peaked at least 300-400 RPM lower. Horsepower came in at 5600 and it was dropping fast by 6000 RPM. Seems like an awfully narrow powerband.
So bringing this back up since I went to the track Friday night...
looking at my graph has me thinking, peak torque at 4700 RPM with such a small cam and the small valved 862s??? I think it would have peaked at least 300-400 RPM lower. Horsepower came in at 5600 and it was dropping fast by 6000 RPM. Seems like an awfully narrow powerband.
That's the problem with advancing the cam that much. It narrows the powerband.
Change the heads and put that other cam in that you have. You will also need more converter for it.
Did a compression test last week, seems healthy. Number 8 is slightly lower than the rest, I forgot about trying some WD40 in the cylinder to see if it would come up any. (rings) I'll have to redo it someday that I'm feeling extra ambitious. Oil pressure is still rock solid, doesn't overheat - even in the FL summer.
The more I look at the graph, it doesn't look like it's falling off much at 6000. (blue line - graph is on post #20 of this thread)) I'm going to try raising my shift points to get some more ET and MPH out of it. I want to attempt to squeeze every bit out of it before I retire the heads and cam currently installed. It's easy to throw parts at it, I'd like to see if there's anything that I am missing and learn from it. I ordered HP Tuners this morning so I can at least data log.
Last edited by Bluecollar Hotrods; 06-25-2023 at 11:28 AM.
01-20-2023, 02:07 PM
