Hey guys, wondering why I'm hearing from people on forums and in person that the lt1 is a lighter crank and you can't use a normal 350 sb crank. I guess that might make sense if I was keeping the stock rods or piston set up but I'm going to use a callies dragonslayer crank, oliver rods, and diamond or JE pistons. I guess my real question is after the lt1 block I have is torn down, squared, decked and splayed mains, bored .030 over, stroked to 3.75 inches with 5.895 or 6 inch rods is running an lt1 specific crank balanced for an lt1 really necessary?

Thanks,
Doug

 

The caution is related to direct substitution of a 350 crank in a stock LT1 and vice a versa. It has nothing to do with a built motor. Actually, the LT1 crank is not "lighter".... it is balanced for the lighter components (con rods, pistons) in the LT1 compared to a Gen 1 SBC 350.

Here's a quote from a good article on "rebuilding the LT1":

Your shop will determine if it's going to be internally balanced (unlike a Gen 1 SBC or LT1), or externally balanced using the stock LT1 weighted flywheel (or flex-plate), and proceed accordingly.

 

All cranks for the late model LT1 come internally balanced in front and externally balanced in the rear just like the stock engine. However you can get any crank fully internally balanced you just have to get your flywheel/flexplate balanced to match. I had my Howards Tracksmart 4340 forged crank fully internal balanced and my SPEC billet flywheel balanced to match.

 

"internal" balance to neutral vs a stock crank/motor which is 'external" balaced with a weighted flexplate/flywheel. That is why a stock flexplate has a weight riveted on it and the stock flywheel as a weight cast into it.

for "internally" balanced motors you use a neutral aka zero balanced flexplate or FW. You can have a stock FW zero balanced or buy a aftermarket one. those have weight that unscrew so they can be used either on external or internal balanced motors. With that said about aftermarket FW's advertised as "neutral" balanced....have that cnofirmd at a machine shop. for example the billet "neutral" FW i got with my McLeod twin disc clutch was 26 grms out of balance from being neutral...why?...because the 4 holes where the weight was attached for external balance = 26 grms of material...so it is always advised to have the flexplate or FW confirmed that it is zero balance by a machine shp if going with a internal balanced motor.