AusScarab29

underpsi68

I believe MER made 850 with stock block. Dart sells a replacement block now.

Ryan00TJ

iTrader: (8)

World and PSI also cast aftermarket 8.1 blocks. The block is very strong. 4 bolt main caps on all.
1-5. Also 18vs16 cylinder head bolts. It is a thin wall non siamesed design vs a 502 block. I would question Raylar/Whipple on capability at 800hp.

BUP

iTrader: (9)

if you are going to do a ground up build I would move away from the 496 platform all together. The stock 496 GM block nor the 496 crank not hold up to big levels of power and tq. The intake and heads are limiting factors as well.

Again if a ground up build, I would move on and away from the 496 getting a dart Big M block and and strong crank for a 565 or something along those lines that would offer better longevity pushing that amount hp / tq. Some high performance engine builders look at the 496 as the red headed step child engine and do not what to mess with it for big power gains..

Also there is alot more performance part upgrades in the history for the old standard big blocks than the 496 would ever have, Plus so many builders whom know the old standard big blocks inside and out compared to the 496.

from experience and reliability, the 496 is best suited in OEM stock form.

Keith Atlanta

The Good:
1. You can safely go to 800-850 HP on the stock block and forged crank/forged rotating assy.
2. A new Big M block from Dart costs the same whether its Gen IV, V, VI or Gen VII 496/8.1 Depending on options it could go a couple hundred either way.
3. If you choose to do a Dart block Gen VII you can go up to 4.625 bore and whatever stroke you want, whatever power you want. Up to 632 Cu In
4. Its a closed cooled platform
5. Its currently easy to find used parts and blocks thru internet/craigslist
6. Several of the closed cooling parts cross over to other merc and volvo platforms.
7. Aftermarket performance parts availability is affordable and easy.
8. Use same headers as other big blocks.

And the Bad:
1. Chevy doesnt make this platform anymore.
2. At the 850 barrier, few have upgraded to the Dart block (however some have with good results)
3. Aftermarket parts availability is out there but there arent 50 different manufacturers for each one.
4. Engine builders dont like the platform.
5. The block is thin. There are several stories of the block breaking at the engine mount.
6. Limited selection on aftermarket performance parts.
7. You can do Dart Heads or Raylar heads, pick your poison. You are kind of limited here. But there are many CNC porting programs out there to make them breath better.

My opinion: It costs the same on the Gen VII 8.1/496 to make up to 700HP as any other fuel injected platform.

Ryan00TJ

iTrader: (8)

The OP already has a forged Raylar stroker rotating assembly and Raylar cam/heads. He's committed to the 8.1 platform. Your mainstream engine builders shy away from the 8.1 due to their inability to tune a modified setup. Whipple and Precision Marine are the only two shops who can modify PCM555. Tuning is the biggest barrier on this platform. Much easier/cheaper for them to build/tune an earlier gen bbc.

The stock 8.1 block is bore limited to about 4.280". 4.290" if you want to push it. The aftermarket blocks allow you to really open up the bore and power potential.


Ausscarab, Your stock closed cooling heat exchanger will not be adequate with 800hp. Look into upgrading to a SenDure #15006-1-5. Its a 5" heat exchanger that is plug and play. Whipple recommends it.

BUP

iTrader: (9)

You forgot one other person in the mix whom can even bring back totally dead / bad PCM 555 controllers and can even do the tunes including reprogram the stock tune into a blank 555. So currently there is 3 but only 2 that can bring back a totally DEAD / bad 555 -- and ECM 555 as well. Maybe someone will chime in whom that other person is haha.

BUP

iTrader: (9)

I would really have to ask is there a person whom can really tune a stock PCM 555 for 800 plus hp that was stock based for 425 hp ? IMO one would be better off with a stand alone ecm system / set up and of course a big upgraded fuel system as well.

I do like the closed cooling for marine apps. Actually I would not go back without it for any current engine build.

Inland area Volvo Penta 496 apps MOST are not closed cooled but most Ocean area Volvo Penta s are closed cooled. In my area most Volvo 496 s are NOT closed cooled, It is a standard set up for Merc 496 apps .

Ryan how did you know he the op has upgraded parts already ?? I did not see that at all . And you are correct on the stock block / bore sizing. Yes aftermarket blocks IMO,, I do like the Dart block for the 496. Actually the marine OEMs are using it for 496 replacements in their repower line ups since GM is long gone with it.

dbkski

iTrader: (1)

Reading comprehension.

2.3 L whipple on 496

AusScarab29