Seen several other 8.1L trucks run in the low 15's and a couple in the high 14's. 2000' will hurt, but not like hear in Denver. My 8.1 still ran 16.4 up hear at 6000'. I think the 8.1 in the burban might have a lot of Tq managment, and could be detuned because the 4L80E. I think the trucks have less Tq managment. Even with the diablo it didn't feel like I got WOT all at once. Tried to get someone to crawl under there an watch the throttle open while I floored it but no luck

 

LOL..... yea im going to get a tune. We played with Hp some but i have no clue what im doing. I will not spinn, even in the rain nothign happens. 3ed gear pulls like crazy but the fisrt sucks and second suck. At the track it was picking up 45-48 mph from the 1/8 to the 1/4 where it was trapping 80-81 mph some something not what it should be.

whats real strange is the wife armada runs 15.8's, but from a roll say 70 to 100 the suburban walks the armada until i hit the speed limitor and she passes me back.

ive talked to trick mount a few times... might have to do something with them

 

lo&slowSierra: about the trans.. I would get a built 4L60e. The thing I would make sure of is that all the internals are built components. Input and out put sprags and servos. I was talking to Chris (thunder550) and the input sprag on his 4L80e broke and thats y his tranny quit. He also has a turbo 408 tho haha. I would do the 60e and see where it takes u. I think thats what Im gonna do when I get my hands on a 6.0

 

yea, just i dunno who to trust with getting a tranny from, and which stage i should go with, having my teeth shatter everytime it shifts dont bother me, i just dont want to have problems with my stuff, i plan on getting a tranny first cause i have a feelin my is ready to die with a almost bone stock 4.8, and then hopefully get hold of efi live and then a 6.0 so i can reflash the pcm, i want have to tune anything if i put in a built trans will i?

 

I have a friend that just got a trans for a turbed Z28. its making 550 whp but the company that built it also does 4L60E, 4L80E and the new 6L90E... I think he said there are 3 options. a 500hp package, 800hp, and 1000+hp

he is on nite shift so when he gets up ill ask him..

 

You can get a lot of cubes with a 6.2 block with a 4" or 4.25" crank. Plus with the L-92 heads aftermarket support that is only there for chevy. Want a turbo, supercharger? If it doesn't fit a chevy it does not exist.

Magna Charger just put to gather a LSX supercharged motor with a 1000 HP on tap on 100 octane. So lets take it down a notch to the real world a simple 408 with L-92 heads and 10psi usually puts over 600 to the wheels on 92 octane.

 

I have to wonder if anybody has worked over a set of the 8.1L heads? Or what does a stock 8.1L head flow? I know that CompCams offers camshafts for them.

They have a 4.25" bore and a 4.37" stroke. The block should be able to take a .060 overbore to get 510cid. I don't even know if it is a tall deck block, or not. An older tall deck block can easily take a 4.5" stroke.

I have to wonder if anybody has converted an 8.1 to older style heads/intake/cam/headers?

 

I worked over the heads on my truck, put 2.19 intake valves with 1.80 exhaust valves up from 2.06 and 1.70. Put 11/32 valve guides necked down from 3/8. I cleaned up the port bowls a good bit and opened up the exhaust port big time. Theses heads are absolute junk on the exhaust side, the intakes are pretty decent as they are more or less big lsx cathederal port intake runners. The deck height I believe is a 9.8" which is a short deck but im not sure so dont quote me. I know raylar had callies make them a 4.5" stroked crank, which with a .030 over bore I believe is a 522ci.....which just happens to be my next set up. It really doesnt make much sense to convert an 8.1 to old style bbc heads and intake....ya maybe cause the head selection is better but the 8.1 has i think 2 extra head bolt holes which dont line up. What I really need to do is go down my shop and **** around with an 8.1 block i got down there, i got bbc parts everywhere so ill experiment and let u know for sure.

Alex

 

The Mark-VII big block is non-siamesed and has a tall deck (10.2"). It has a unique head bolt pattern, it's not just the two extra holes that make it different.
It will accept the same size overbores as a Mark IV-VI 454 block (standard deck). Both the 496 and the 454 have 4.25" bores but the 496 has a 4.37" stroke instead of a 454's 4.00" stroke.

 

Getting a set of cnc'ed ones for my truck since the raylars are expensive