Is the 496 or 502 based motors better to build off of. I have a pair of 496 motors with carb intakes and msd distributors. Are the 496 exhaust the same as a 454/502 or different? Also these motors are 30 over and need rebuilt again. My question is do I find 502 blocks to build off or build the 496's. Seems like the 496 is its own motor and nothing in common with the 454/502 motors?

what 496's are they? I always thought a 496 was a stroked sixty over 454 which in my mind would be a throw away motor at that bore. Do you have the 8.1 Vortech based blocks?

GD he listed the 496 with MSD ignition set up and Carb / intake so no way its the 8.1 MPI distributorless 496 CID from 2001 thru 2010 from Mercruiser,

The 496 carb with a distributor ignition is bored and stroked based from a 454 / 7.4 L.

I think gm performance offered the 8.1 Voetech as a carb motor

Looking at the years of his boats in his profile, I would guess he has stroked 454's.

They are the 8.1 based motor with carb intake

If a bored and stroked 496 it's a good engine. If factory 496 don't bother with them. Go with a 502.

what exactly is the 8.1 Vortech and what was its purpose as opposed to the 502, how does it differ from the rest of GM's big block? Just curious really

2500+3500HD trucks with more modern FI and cats. That's what it's purpose was.

Luckily GM kept the 502 for over the counter sales. Boats / old cars/tucks / etc.

The 8.1L isn't 'bad' but.........

OK I am lost now you have a 496 - 8.1 L base like what was used in the marine apps from 2001 thru 2013 (Volvo bought a bunch of stock to keep them going)

You are saying Carb app and intake so what ignition set up did you use. I might be wrong but if I remember correctly the cam for a 8.1 L - 496 does not even have a gear to match up with a distributor hence a true 496 stock base used coil over plug. Do you have a MSD set up with a crank trigger and coils over plugs along with the rest of the MSD ignition components ? Just asking.

I do not recall GM offering a crate engine OEM 496 CID 8.1 matched up with a carb intake or even having a carb intake for the 496 - 8.1 L. .

Also Dart has a lot to offer to change over the 496 MPI to carb app. Maybe this is what you have.