Subject pretty much says it all, I've been thinking about future mods for my 396... one of those is adding a 4" or 4.25" crank. The only thing I'm not too sure about is if its worth doing all the work (if its even doable) to a smaller bore motor (its .040 right now, putting it at 4.134")

Am I thinking right here? If I'm going to stroke something should I be looking at 4.250"+ of bore?
The 396 I have is cast # 3902406, which is pretty much the same as the 65-66 (date code is '67) from my understanding. Could I take it .100 out (counting the .040 over now) and be happy with 4.194" of bore, and 4" or 4.25" of stroke? Will that casting hold up to the output?

Just thinking outloud here!

Thanks guys

In the grand scheme of things it would probably be cheaper and less work to get a 454 block and crank. You would also end up with more displacement.

There are lots of things you could say, the cylinder bore is smaller so that will shroud the valves, you will have to clearance to the block for the larger crank. You might have heat issues if you push the cylinder walls to thin, all kinds of stuff.

Daniel

well, the sbc 427 has a 4.125/4 bore/stroke and it works kinda well...

Indeed, I've seen 454's left and right dirt cheap around here, but I've got alot of work into this block. From everything I've read the 65-66 (and some early '67 models cast in 66?) have "extra" meat in the cylinders, I've talked to a few people running their early BB's .125" over with no heating/weakness issue (including early BB's and some 454 castings)

pdq67 had mentioned something in a previous post (here or team camaro) about a 396 MAYBE swallowing a 4.00" rotating assy?

I guess I forgot about the sbc 427, if I even went with the 4.134" bore I've got now, and 4.00" stroke that'd be 430cid or so.... mmmmm yummy!

When the bottom end is done, the 206 castings will get some attention, lots actually smile.gif (cfm performance sure looks good)

Thanks again guys

Per a reference I have, casting number 3855961 was the only block used for both 396 and 427 engines in '65 (396 only) and '66.

I'm thinking you would need some custom pistons, and I would want to make sure that you have the clearance for the crank/con rod before ordering them. My machine shop usally orders extra pistons when going custom, as you have to order 4 minimum if you should have a problem later down the road. Unless you are going all out, IMO the shrouding probably doesn't make a huge hp difference. But by the time you do all this it might be just as cheap to go 454 and you will have 30 extra cubes for about the same money.

I'm thinking you guys are probably right, I should just find a decent 454 to start building up... it'll be a lil easier that way, no down time smile.gif

Thanks for all the input everyone, I love TC tongue.gif