I have set in stone that i will be putting a BBC in my car. question is, what block should i start out with? Dart big M? - $2300 Merlin III? - $2200 Merlin III Street? - $1800. looking at a 9.8" deck, but this will not be a drag car, it will my 10sec (or faster) daily driver i don't think i'll ever go over 1000hp while i own the block, it will probably never see more than pump gas N/A. MAYBE a bit of nitrous, but i doubt that. and possibly a blower in the future, but also highly unlikely. the more expensive merlin block has .050 thicker walls (.250" @ 4.625" bore), but the street blcok has OEM wall thickness (.200" @ 4.625" bore) my basic plan is a sturdy forged bottom end (540 CID), brodix heads, and a solid roller cam. advice welcome! josh.

I have no idea the difference between the Merlin III and Merlin III Street but when I bought a new block, it was either going to be the Merlin III or the Dart Big M.

The Big M is a far better block. I've abused mine and it's still holding up.

i looked a little deeper, and the dart block has finished cylinder bores, and the merlin III does not. how well can you trust the finish on the dart block? will it be worth a little extra to save on out-of-the-box machine work?

i didn't notice before, but the dart block also has .300" thick cylinder walls @ 4.625" bore. +2 for the dart block.

but like i said, this is a daily driver (to me at least) motor, and probably always will be.

My block wasn't finished.

The block needed to be bored out to 4.500. It comes with 4.490". Cam bearings needed to be installed. Frost plugs needed to be installed. Oil gallery plugs needed to be installed.

where can you get an unfinished dart big m? would it be cost effective to have a machine shop do all the work rather than dart?

A machine shop should be finishing the work anyway. You can't bore and hone a block properly without having the pistons to test the fit.

so i guess the dart is the best bang for the buck?

As far as I was concerned, Dart was a better casting. Not all castings are the same. Dart has features that other blocks don't have. It's also a very beefy block. The bare block was 260 pounds.

well i guess it'll be a dart block then. what is the max "recommended" HP? What kind of clearencing work would need to be done to get a 4.375 stroke crank in there? how about a 4.5" stroke?

i have all of a sudden become addicted to cubic inches...

I'm making around 850 HP naturally aspirated with mine with no problems but it's not streetable.

A 4-3/8" stroke can easily be done. If you want to go to 4-1/2" stroke, you need to use a tall deck block. With a tall deck block, 572 and 632 are the common sizes.

With what I have invested in my engine, it's already worth around $20,000. It can be a lot cheaper to just buy a pre-assembled engine.