will a 1985 350 crank interchange on a 1985 305 motor?

Jonh Lingenfelter on modifying small-block chevy engines page 30 said :
"The impostor"
"Both same main ,rod jornals ,stroke and even the same casting #(3932442).Unfortunately,even though they can and are used interchangeably ,they are not identical" .
"The differencelies in the way the cranks are balanced for the diffeerent reciprocating masses of the two engines.the main difference between the 305 and the 350 is the diameter and weight of the 350's larger bore pistons.this crank is also used in the obscure '79-'80 267cid 3.48-inch stroke engines".
"In mild street applications,the 305 crank can be used with stock weight replacement pistons allowing the rotaring mass to be propertly balanced.Unfortunately, when high performance rods and/or pistons are added, the weight difference will require expensive "heavy metal" to properly balance the crank".

"THE BEST WAYto spot a 305 without having to spin it up on a balancing maching is to lay the crank down horizontally and position a straightedge along the machined surfaces of the crank . aA 305 crank will allow the straightedge to lay flat across all five points .A 350 crank will not allow the straightedge to sit flat"

I hope this helps .

Would just like to add that I have proven every single published method of ID'ing a 305 crank wrong in a couple of instances. The ONLY way to tell is to put it on the balancer and spin it, period.
The 305 cranks are actually nice to use with most of the lighter weight pistons that are being manufactured lately, makes the balancing a bit easier.

so can i get away with using a 350 crank in a 305 engine? :confused:

Originally posted by bowtie455:
so can i get away with using a 350 crank in a 305 engine? :confused: =
I wouldn't.
Yes it will physically fit but,,,,
it is usually not a good idea unless you are going to have the engine balanced.

It is the same casting number but is balanced for heavier parts

And Bill is correct as usual, the only positive way to tell the difference is to spin it in a balancer regardless of what all the articles on how to ID them say.

not to bust on you. but why dont u just build a 350. i mean, for the amount of money it would take to get a 350 crank and everything all balanced, u could build yourself a little 300hp 350.

aaron

I built a 350 years ago with a 305 crank. With aftermarket +.030 350 pistons. It ran well and made good power but did have a slight vibration at about 2500 rpms, the vibration went away at all other engine speeds and I shifted it at 6500. Lost a rod in that engine that might have been related to the imbalance.