305/350 crank

[Steve Williams]

Originally Posted by BillK

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

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.

[BillK]

Originally Posted by Steve Williams

Bill,

The differences go further than just balance.

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,

[Steve Williams]

Originally Posted by BillK

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,

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.

[BillK]

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,

[carl hinkson]

Originally Posted by billk

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,

x10000000