what heads are you going to use and what kind of comp do you want
700hp is easy with a 4.150

I was looking at overlap drawings of crankshafts and noticed the 4.5" crank I was wanting to run has a very small overlap and seems kind of weak looking to me. If someone could shed some light on what would be the best compromise between stroke length and crankshaft strength. I want as many c.I. like anyone else but I don't want a crank that I am afraid of breaking when I put nitrous on the motor. I plan on making around 700hp n/a then some nitrous once everything is sorted out.

Technically speaking, the less rod/main journal overlap the less stuctural integrity of the crankshaft, yes. But this does not mean in-and-of-itself that a crankshaft "isn't strong" per se....regardless of manufacturer and/or brand application. But...one may indeed deduce that a crankshaft with less journal overlap is likely not as strong as an equivalent crankshaft with more journal overlap.  That much is obvious.

Most offshore cast stroker cranks for the BBF that are 4.500 stroke are "rated" to 700+ hp. That being said, I have seen more broken crankshafts, more windowed cylinders, more burnt valves, more blown head gaskets, etc, from nitrous oxide than any other form of power adder. Therefore, if you want to have 700 hp + nitrous oxide then I would insist on a forged crankshaft,....I don't care how much or how little journal overlap there is.

LO

So let's say that I choose not to run nitrous down the road and I just upgrade cylinder heads later instead. Would a good cast scat crank fit the bill? 1k for a crank is a little out of my budget at the moment but I want a strong setup.

yes


700hp with dove heads is a tall order in a jet boat
 lakes built a 521 (ithink) for dan hurcules and it makes over 700hp on pump gas but, it has good heads

lakes, the amount of port work that is needed to get to 700 hp with the dove heads is a lot $$ wise dont you think

On my next engine, I want to go forged 4.3 stroke and run P51 heads. I will give you a call Paul when I get ready to do that.

Port the heads before you do the valve job.

That's some good power. What kind of camshaft and intake?

If someone could shed some light on what would be the best compromise between stroke length and crankshaft strength.

This depends on application, combination, etc.  Generally speaking, I reallly like the 4.3 stroke/6.8 rod combo for several reasons, including pin placemernt at BDC, rod ratio, power producing capabilities, etc. It's an "overall" winning combo and works great in a jet boat.

I have been thinking and I will just set aside 1k for the crank and balancing. There is no need to do this twice.

bbfsounthwind, are you aware that you cannot just purchase a crankshaft and re-use your 460 rods and pistons?  If you use a stroker crank, then you also need stroker-specific connecting rods and stroker-specific pistons.  Quality, brand name complete stroker kits (crank/rods/pistons/rings/bearings) run about $1699, and $400-$500 more for the 4340 forged crankshaft.  Then add the balancing, mallory metal, boring the block, etc.

LO

copied from 460ford.com
For(d) easy reference;(formula......Bore X Bore X Stroke X .7854 X 8 )

Stroke (in.) Bore (in.) Overbore (in.) Displacement (cu. in.)

3.590 4.360 stock 429


3.850 4.360 stock 460


3.850 4.390 0.030 466


3.850 4.400 0.040 468


3.850 4.420 0.060 473


3.850 4.440 0.080 477


4.140 4.360 stock 494


4.140 4.390 0.030 501


4.140 4.400 0.040 503


4.140 4.420 0.060 508


4.140 4.440 0.080 513


4.300 4.360 stock 514


4.300 4.390 0.030 521


4.300 4.400 0.040 523


4.300 4.420 0.060 528


4.300 4.440 0.080 533


4.500 4.360 stock 537


4.500 4.390 0.030 545


4.400 4.400 0.040 547


4.500 4.420 0.060 552


4.500 4.440 0.080 557

Shitcan the nitrous and the heads, and buy a set of aluminum heads.
Save the money from porting and the nitrous, and have a better all around engine longterm

the intake is a weiand tunnel ram, 2-750 holly double pumpers. Cam is a comp-cam solid roller lift is 726, duration is 268 intake, 276 exhaust, 108 lobe separation.

I went with the 4.500 and bored the block .030 over and ended up with a 545 cid. I could not be happier! Right now as it sits it is @ 11.23:1 compression and this winter I am going to 14:1. As it sits now I pull a detailed bronze B impellor to anywhere between 6300 to 6500 rpm. Make sure you get a dished piston or your compression will be through the roof!