305/350 crank
 

Got a street 305 Chevy im rebuilding.It had a bad crank,so I came across a 350 crank which is the same stroke.Can I use the 350 crank ,or will it have a balance problem?Dont really want to spend the money to balance it. thanks

Re: 305/350 crank
 

Lyn,
The 350 and 305 cranks that I have done have been quite a bit different in balance. If you are replacing pistons it seems like they are making even the stock replacement pistons a lot lighter so that will make the problem even worse.

I would say it would be worth having it at least checked. You probably don't have to do the entire balance job, making all of the rods and pistons the same weight etc. Just use one of the 305 assemblies as a reference to make the bobweight.

Hope this helps,

Re: 305/350 crank
 

I cant say for sure what a 350 crank in a 305 will do. But I know for a fact that a 305 crank in a 350 will vibrate at around 2500-3000 RPM. Bad enough that you will take it back apart.

Re: 305/350 crank
 

The 305 crank with 350 rod-piston is a problem. The 350 crank with a 305 rod-piston is not a problem. No balancing required for a stock piston or cast replacement. The 305 crank is the nastiest piece of junk that is associated with Small Blocks IMHO.

Re: 305/350 crank
 

Dont forget the 262 and 267 ci motors as candidate for piece of junk award

Re: 305/350 crank
 

305-350 cast cranks were the same casting number and the only difference was the factory balancing. If I recall correct the casting number was 448...last 3 and if you look at the depth of the holes on cranks from a 305 vs a 350 you wll see a big difference in hole depth....the 305 bobweight was lighter so the crank had deeper balance holes drilled.

You could use either crank in either engine but needed to address the balance issue......

There is no difference in the counterweight overall diameter that I can ever recall....

Re: 305/350 crank
 

Steve,
Other than the balancing there is absolutely no difference between the two crankshafts.

I just looked through some old balance cards and found a 305. The piston and pin was about 60 grams lighter than most of the stock type 350's I have done. 622 grams compared to 682 for the 350 If that is not enough to make you believe that the 350 crank needs to be rebalanced to use in a 305, then I don't know what is :)

Re: 305/350 crank
 

267,305,350 all are same crank, EXCEPT for balance,you can identify them by comparing counterweights,267 will have deepest holes,305 a little less, some 267/305 cranks have notches cut in counterweights to remove weight.

I would at least try to find 305 crank, or balance the 350 crank,I balance everything,be surprised how good a 3.5 briggs will cut grass when balanced,took 2- 3/4X3/4 pieces of heavy metal.
Might get someone to balance w/bobweight made up from 1 piston/rod.

Mike Taylor 3601

Re: 305/350 crank
 

Some of the rebuilder manufacturers make 305 pistons that are purposefully heavy for use with a 350 crank in a 305 block.

Re: 305/350 crank
 

I have balanced a few cranks for other shops and the F/M 345 pistons are now appox.72 grams lighter then the older ones.

Re: 305/350 crank
 

Bill,

The differences go further than just balance. The use of a 350 crank in a 305 has been done several times in our shop and with a cast replacement piston, I never sent one out for balance. The advice of my crankshaft guy was that 305 cranks rotating 350 rod-piston was a problem, but 350 crank in 305 with cast piston or cast replacement was not a problem provided it was a stock rebuild, stock intended RPM range. As far as the weight difference between the two engines, I don't recall what the exact number was, but it seemed it was much closer than 60. I want to say it was 46 or 48. I can tell you that the 305 crank, if used in a 350, will have a bunch of mallory in it. Built one for a customer who supplied this balanced assembly. He knew nothing of what the crank was until we looked it over closely and told him. The amount of mallory was a dead give away that something wasn't right.

Re: 305/350 crank
 

Steve,
Not sure what you mean by this ???? They are both the same exact castings. The 305 cranks have more metal machined out of the counterweights but other than that they start out as the same piece.

I tend not to take chances on balance. The first time I would put a 350 crank in a 305, I guarantee you the thing would vibrate ... :( Why even take the chance anyway ?? Balance it and be done with it.

There are also too many variations in stock piston weights to take a chance. Some of the late model 350 pistons are really light compared to the early ones. If I don't know where a crank came from, I will recommend balancing it, period.

Just my opinion,

Re: 305/350 crank
 

Bill, I will try to upload a couple of pictures I have of the same casting number crank, one a 305 and the other a 350. The differences are more than you think. This also pointed out to me from my crank guy.

Re: 305/350 crank
 

Steve,
I just remembered I have a "known" 305 crank out of a Mercruiser 305 I am doing for customer. I will have to take a look at it in the AM. I probably have 5 350 cranks to compare it to. Please try to post your pics also, I am always game to learn :)

Happy New Year,

Re: 305/350 crank
 

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