[efurlong]

I'm in the process of building / buying a SBC 400 based short block. Either a "bow tie" 421 from Skip White Performance or a Dart 427 from Terry Rosebush Motorsports. The 421 has a 3.85 stroke, the 427 has a 4.00 stroke. Is there any disadvantage to a 4.00 stroke in a SBC? I've heard that the 4'' stroke is less reliable...why would it? The same builder says that a 4'' stroke creates "smokey" start ups? Chevy never produced a stroke bigger than 3.75..is that the "edge of reliability? In other words, is there any down side to either a 3.85 or a 4.00 stroke in a SBC? Thanks

[ericnova72]

Only reliability problem with 4" stroke is block strength of a stock block, the power you can make is more than the stock block can reliably handle. If you do it in an aftermarket block there are no worries there. Piston and ring technology has gotten to the point where oil control is no longer a problem either, so don't worry about "smoky-ness".

About the only problem to longer than 3.75" strokes is getting it all to fit in the block and clear everything, just requires more care in choosing parts and more work in clearancing everything.

[Oldrusty]

I have a 409 sbc 4.035 bore 4.00 stroke. No smokey starts has been very reliable turning 7500rpm sled pulling. I like the high piston speeds without having to turn the motor over 8000rpm. You get alot of signal to the carb and with the shorter dwell time i think they are more detonation resistant since the pistons cool quicker. But as others said its alot to fit in the block. mine is a stock 2 bolt main with splayed billet caps, has held up so far to street driving and 40 hooks to the sled. theres alot of material removed from my block i will say that.

[curtis73]

"reliability" of 4" cranks has to do with journal overlap. The more stroke you have, the less material is overlapping the main and rod journals which asks the counterweights to be more responsible for holding the inertia. Make sense? If not I can make a drawing.

4" stroke shouldn't be "smoky" unless you assemble it with really short rods which would increase side loads on the cylinders.... or the builder could be referring to the fact that the pins will be intruding on the oil ring... but careful assembly shouldn't be any smokier than a stock stroke.

[ap72]

You'll have a shorter skirt, worse rod angle, and a pin into the oil ring package- I would start with the assumption there will be some oil consumption, and be pleasantly surprised if there isn't. Assuming you won't have any issues when you change all of these things is shooting blind and hoping to hit the target.

Stepping up in the level of block preperation, ring selection, rod, and piston design can help mitigate oil consumption but it will need attention if you wish to avoid it.

Some people will just run the cheapest parts they can find and plan to put in an extra 2 quarts between oil changes- either choice is understandable.

[CNC BLOCKS NE]

Originally Posted by efurlong

I'm in the process of building / buying a SBC 400 based short block. Either a "bow tie" 421 from Skip White Performance or a Dart 427 from Terry Rosebush Motorsports. The 421 has a 3.85 stroke, the 427 has a 4.00 stroke. Is there any disadvantage to a 4.00 stroke in a SBC? I've heard that the 4'' stroke is less reliable...why would it? The same builder says that a 4'' stroke creates "smokey" start ups? Chevy never produced a stroke bigger than 3.75..is that the "edge of reliability? In other words, is there any down side to either a 3.85 or a 4.00 stroke in a SBC? Thanks

Make sure the one from Skip is a 4 bolt bowtie and and not a 2 bolt!!!

[CNC BLOCKS NE]

Originally Posted by efurlong

I'm in the process of building / buying a SBC 400 based short block. Either a "bow tie" 421 from Skip White Performance or a Dart 427 from Terry Rosebush Motorsports. The 421 has a 3.85 stroke, the 427 has a 4.00 stroke. Is there any disadvantage to a 4.00 stroke in a SBC? I've heard that the 4'' stroke is less reliable...why would it? The same builder says that a 4'' stroke creates "smokey" start ups? Chevy never produced a stroke bigger than 3.75..is that the "edge of reliability? In other words, is there any down side to either a 3.85 or a 4.00 stroke in a SBC? Thanks

FWIW we just built a 421 using a Dart SHP block and we ened up using a Callies rotator with Dragon Slayer 3.875 crank, 6 inch Callies Compstar and Mahle pistons and we use a .420 lobe with a 1.000 base circle and we had .048 cam to rod clearance.

I am not a big fan of putting 4.00 arm in a 9.000 deck block!!!

[cobalt327]

I would tend to agree. That's one reason Dart has their tall deck SBC Iron Eagle block. Has relocated 2" cam journals, too- along w/priority main oiling and a host of improvements. ~$3K, give or take.

But once you're in THIS territory, the question then becomes (for me, at least)- why not go w/an OEM block 454 BBC and run it out to a 496.

[ap72]

Originally Posted by cobalt327

I would tend to agree. That's one reason Dart has their tall deck SBC Iron Eagle block. Has relocated 2" cam journals, too- along w/priority main oiling and a host of improvements. ~$3K, give or take.

But once you're in THIS territory, the question then becomes (for me, at least)- why not go w/an OEM block 454 BBC and run it out to a 496.

Why not an OEM 502 block?

No matter how much we do there will always be "why not's" and "what if's".

[cobalt327]

Originally Posted by ap72

Why not an OEM 502 block?

The MAIN point I was making, is there comes a point (about 406 cid for me) where a bigger and bigger SBC stops making sense and simply building a BBC starts to make more sense.

But otherwise, sure.

[spinn]

If building a road car , the stroke can often offset the need for lower gears in the rear. The engines stroke also should give the intention of the rpm useage. A large stroke performs well under mild builds with RV cams. GM sells a 383 with a oe style cam and it works awesome.

The 350 in particular needs help from 1000-3000rpm. Vortec heads and mild cam help, but not as much as a 3.75" crank. A drag racer does not notice with a 3500rpm stalled launch. 1000-3000 is where your driving RPMs occur. If this a driven road car that is a good place to put your money.