4.375 Stroke in Stock Block

[FirstEliminator]

The 4.25 stroke is very common. Looking at a chart on Barry's website that shows the cubic inches of the various combinations shows a 4.375 stroke. Does the 4.375 drop in like the 4.25? Is there any special work needed to accommodate the 4.375?

  thanks,
     Mark

[blykins]

The crank will most likely be an RPM crankshaft, unless you have Scat make one, or do something custom from another company.  The RPM cranks are very nice, but you can count on them having to be touch ground as they are generally oversized on journal diameters.

As far as fitting, they will drop in and not touch anything on the block.  There have been a few builders report that they have had to clearance a couple of rods to clear the camshaft, but I have never had to do that with an RPM crank and Scat rods.   

[Barry_R]

Brent's comments are same as mine - I have had things get snug on aftermarket blocks but not on stock.  You will be buying custom pistons, and the oil ring gets into the piston pin boss, requiring a spacer ring.  Not my favorite deal but they will work.

[CaptCobrajet]

I use 6.625 rods with the 4.375 cranks, so the oil ring does not require a rail.  Generally, when a steel crank is needed, I upgrade to the forged Crower BB Sportsman rods, so the Pontiac length, BBC crankpin is a great choice on rods with a 4.375 crank.

[Randy]

I used a 4.375 in my 391 block that I made my SOHC motor, it worked fine. I built another motor for a friend of mine and ordered the wrong steel crank 4.375 still have it never used, going to sell it if interested ?

Randy

[Tony Fritz]

Randy,

Contact me if you still have the 4.375 crank available. My email is FRITZAL12@aol.com

Thanks, Tony