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Username Post: SBC 350 main journal diameter -VS- SBC 400 main journal diameter.        (Topic#247365)
Posts: 714

Loc: Central New York
Reg: 07-15-09
08-12-10 11:11 PM - Post#1960261    

I've been looking through a bunch of parts books lately. Looking at different aftermarket blocks and cranks. I've noticed that you can buy a SBC block say a 400 block but with the smaller 2.450" (350) mains instead of the regular 2.650" mains that are standard on the SBC 400. You can even buy a 4.000" stroke crank with the smaller 2.450" mains.

Why would you choose one over the other? What are the pro's and con's of doing it both why's? I'd like to build a big inch small block like a 434 or so some day that'll make an honest 550 HP with gobs of low and mid range torque....and NO SPRAY!, not anytime soon though. Would I be better off buying a Dart or World Products block set up with the 400 (2.650") mains instead of the smaller 2.450" mains?

Thanks, NYH1!

'78 Camaro, mild Vortec head 385 stroker, 9.1 comp. Lunati Voodoo 262/268 hyd. ft. cam, RPM Intake, 650 AVS carb, TH350 Coan 11" 2600 stall, 8.5" 10 bolt. 3:42 posi, 1 5/8" Full length Headers, 2 1/2" Flowmaster Exhaust System.


Honored Member
Posts: 27305
Loc: Katy, Tx, USA
Reg: 07-06-00
08-13-10 05:07 AM - Post#1960310    
    In response to NYH1

The aftermarket just never geared up for the bigger main bearings.

I think the block is going to be stronger with the smaller bearing bores, and the crank will be sufficiently strong. That's one reason the aftermarket makes them that way.

But this is really a matter of available parts. You're pretty much going to have to use what's on the market. Your choices are rather limited with the 2.65" mains.

Dedicated Enthusiast
Posts: 5189

Loc: south western pa.
Reg: 01-25-00
08-13-10 06:04 AM - Post#1960333    
    In response to NYH1

the crank journals have more overlap and are stronger with the larger mains and that was the reason GM did it. larger mains also generate more heat in race engines so take your pick

retired race engine builder,former NASCAR tech inspector. new corvettes owned 1959,1962,1963,1964,1965, 1966,1997,1999,2002,2005, 2008 plus 30+ other chevy cars and trucks along the way. 2008 corvette sold and waiting on a C-7.


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