454 knock - looking for suggestions

Tremek said:

So if I understand correctly mk IV heads can go on a Gen VI block, but not the other way around? What would the advantage be of taking my heads to the Gen VI truck? Also, why 96-01? Looks like the 4L80e started being behind the 454 in '91 if my searching is right?

Click to expand...

MArk IV and gen VI are direct swaps from what I have read, the 91-95 is GenV and is a variant of Mercruiser it requires specific gaskets to use mark IV or Gen VI heads on it. THe 96-01 also has a factory roller cam you dont have to buy expensive retro rollers and can run standard/synthetic oil without looking for zinc or additives. the 96-01 also has SFI using a crank trigger and cam sensor allowing for more control, The 91-95 uses TBI which is under sized for performance big block and is usually swapped to performance small blocks. The ecm is old and hard to find someone with equipment/willing to tune it, the newer ecm can be swapped out to the same ecm being used by LS engines allowing for much more availability to be tuned.

So, quick update - Sunday resulted in an interesting development:



Found a donor motor! In a donor truck! '99 Suburban 2500 LT with 216k miles on the motor, and 40k on a new 4L80e - and a rod knock. OK fine, let's see if we can baby it home.

It briefly moved under its own power:



... until it didn't.



My buddy drafted into helping conveniently in most pics.

OK fine, still $500, I knew I'd be rebuilding either the '77 or spending much more on an already-rebuilt block, but this gives me all the bibs and bobs I'll need to convert the '77 over to a MPFI hydraulic cam/roller setup that can be tuned by HPTuners (might do a 0411 conversion after everything's working, tbd) and, AND, gives me one of the nice-to-haves I have wanted forever in this truck, a 4L80e.

If I'm lucky, the '77's 781 heads can be cleaned up, bigger valves can go in, and the best bit of the '77's drive line can soldier on with the Gen VI setup.

So we have a lot of work ahead of us to pull both motors, clean up the '77's engine bay etc, see if the '99's block is completely trashed or not, but at least I have a complete truck (that's actually in nice shape!) to work from for harness, accessories, etc.



At any rate, my GM collection is growing (Safari is my buddy's, but still.)

Here's the '99's RPO sticker:



Anyone see anything of note? I haven't decoded everything yet.

Has anyone ever done what amounts to a full transplant of all the niceities of a GMT400 big block over to a square body? Hydroboost brakes, modern AC, etc? If so I would love some pointers, not coming up with anything conclusive on search.

Also could use recommendations on what rotating assembly to put into whichever Gen VI block ends up going into this beast - if I want 500hp/500tq (corrected - I'm in CO so at almost 6000' above sea level) as a target for the build, which I realize should be relatively mild, do I need forged pistons and crank?

Thanks again in advance for all your input!

That 99 looks pretty clean with that many miles. It's got 3.73 gears with a peg leg.

Craig85: Thanks, yes it is pretty clean, I feel a little bad about using it as the donor since I know there are guys out there that love these GMT400 2500s, but the price was right and its heart (sort of) shall soldier on for this noble cause.