I have read where taking a 3.75" stroke crank and grinding down the journals to 2.00" allows you to get a 391 instead of a 383. It is also mentioned that it makes for lighter rotating weight versus the standard 383...making it a quicker reving engine. Prices for this aren't much more than a 383, so I am seriously considering this on my current rebuild.

In a car weighing ~3450 lbs that won't see past 5500 rpm much, and definetly not past 6000, how much gain in power or decrease in elapsed time will the "quicker" reving add? How much will this better reving ability be noticed in terms of feel or seat of the pants? Obviously the more volume should add to the potential for more power. Also, is there any longevity/durability issues with the smaller journal on the crank? I assume since the 350 and 400 small blocks have bigger crank journals than the small journal 327 that there must be a good reason for it...possibly for reasons of strength(?)...weaker rods(?).

 

I wouldn't do it. 2.000" rods have 11/32" rod bolts, where the ones for 2.100" journals have 3/8" bolts. It's a typical magazine article trick that produces very slightly more powerful motors that will last a couple of dyno pulls and that's about it. I certainly wouldn't stroke a motor that much using those old weak rods that the factory didn't even think were adequate for a 3.48" stroke, with my own money (unlike the magazine article writers), and count on it to get me to work every day, and then have to fix it (with my own money again) when a rod comes through the side of the oil pan.

 

well some other things to think about would be more rotating weight moved further out would mean more stress on the motors parts.

ex. take your arm touch your hand to your shoulder and then move your arm up and down as fast as you can


try the same thing with your arm streched all the way out... gets a lot hard doesn't it? just think of doing that at 5000 rpms and you see the stress.

finding rods/pistons prolly isn't going to be that easy if you want something more then stock


might you run into rod/block clearance issues?
or maybe rod/cam clearance issues

 

As a result of RB's post, I will stay with the 383. But to reply to the previous post:

The rotating weight would be lighter in this case.
Finding rods and pistons for this application is not difficult. Kits available from a variety of suppliers.
Yes...a bit more clearance issues are involved.

At least according to the trick magazine articles.

 

If you are looking for more displacement, I would suggest going with a 396 stroker. The cranks are not much more if at all for this than the 383.

If you were mostly trying to get less rotating weight for a quicker, higher reving motor, your best bet would be to run light weight pistons. You can lose more weight in the rotating assembly, relieve a little stress from the rest of the internals, and have the benefit of the stronger rod journals. Just my thoughts...

 

weight even though it might be less is still moving it outword (pistons/rods). so I guess I misphrased it you would move the weight out more

also piston speed would go up giving more stress to the rest of the motor