How much HP can a 2 bolt block handle?
 

I still have the original 1990 Merc 454 330HP from my boat in my garage and I'm thinking of building a stroker or possible supercharged engine out of it. The engine dropped the number 7 exhaust valve 2 years ago so I just pulled it and built a new engine. Block is good but it is a 2 bolt block. I want to build a 500-600HP engine.

How much HP will a 2 bolt block with ARP main studs handle?

Or should I just sell it and find a 4 bolt block to start my build?

Michigan Motors will give me $400 for the engine since it is a rebuild-able core.

fixx
 

you sure? every 330 i have worked on has been a 4 bolt main..

yep,never seen a 2 bolt merc big block motor.

I haven't pulled the oil pan yet but I did look up the serial # online and it said it was a 2 bolt

Two issues. 2 bolt block, and its a 22 year old block. Even freshwater rots these blocks out over time.

Id shop craigslist, and find a nice 4 bolt main block, from a car or truck. I found a mint STD bore 4 bolt block on craigslist, for 300 bucks. Was a car block. Looking inside the water jackets, around the cylinders, looked mint.

I also read several places, the last couple years (88-90) the Mark IV production castings werent as thick as the older blocks. Casting #10068286 block is supposed to be thin walled, compared to its predecessors.

I agree with Mild. That block can only go .070 over, and that's if there isn't a bunch of corrosion from the back side of the cylinders. You should be fine with a 2 bolt block at 500-600 hp. However, you have to be sure the cylinder walls are thick enough. You could also either add a main girdle to tie all 5 mains together or convert it to a 4 bolt block. But, by the time you do all of that along with sonic testing and machining, you could probably get a Gen VI block with siamesed cylinders, an extra 50 ci, etc.
Eddie

I had a few 330 merc., 2 bolt main, motor builder dynoed at 550hp back in the day,hard running back then in a heavy boat.
I would say 550 to 600 hp.
I agree about boring, you can also get a soft block.

It's possible it's 2 bolt but as said it wouldn't be practical cost wise. It would be a pleasent surprise if you opened it up and it WAS a 4 bolt!

Thanks for all the info guys! I will open it up later this week. If it is a 4 bolt I think I will keep it. If not I will sell it and start looking for a newer 4 bolt.

fixx
 

4 bolt block will have 2 oil pressure holes on the side of the block above the filter casting..

read the bottom of what picklinjim posted,,

Note,some 1988 standard blocks may have 4 bolt mains..