8BA crank in 59AB?

[Mr 42]

I think it will work but must double check.
I have a 8BA block cracked along the oil pan rail.

But i have a standard-bore 59AB block in nice condition.

Now i am thinking like this, if i take the crank and rods from the 8BA.
Will the crank and rods a bolt in?

I know i need to change the cam gear on the crank.

[Mart]

Hello Lars. I believe it will go in, but it depends if your 59A motor is set up for a rear rope seal. If not you need the aluminium seal holders for the rope seals. I was thinking of doing something similar myself and that is what I understand it needs.

[Mr 42]

Thanks Mart.
That was my thoughts too.
We will see if the guys on the other side of the pong agrees when they wake up ;-)

[rotorwrench]

The cranks are pretty much interchangeable with only the exception of the difference in crank journal oil passages. Either 59A or 8BA con rods will work for the 8BA or 8CM type cranks but the insert bearings of the 8BA con rods won't work with the 59 series crank since they only have the one oil passage per crank pin.

There can be differences with some Canadian made cranks (69A) but the USA ones are predictable.

Also, some 59 series blocks were actually 41A 221 CID blocks so a person has to watch out for those.

[Bored&Stroked]

The only other thing to note is the crank gear on the 8BA crank has opposite thrust to the 32-48 cranks. My recommendation (if you're running a 59x front mount distributor and timing cover) is to put the 59x crank gear on the 8BA crank - this puts the thrust toward the block. This also lets you use the 59x timing gear and cam . . .

[weldor2]

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rotorwrench, what's the reason for not being able to use an 8BA crank in a 41A block

[Desoto291Hemi]

I was thinking there was a slight difference in the rear main bearing ?
I think it is a different part #,,,,,the rear bearing ?
I could be wrong.

Tommy

[V8COOPMAN]

Originally Posted by weldor2

rotorwrench, what's the reason for not being able to use an 8BA crank in a 41A block

I don't believe the big end of the 8BA rods will fit down through that 3-1/16" bore. DD

[rotorwrench]

A 8BA crank can be made to fit about any of the older flathead blocks but it isn't a bolt in to all of them. Some of the older blocks have smaller bearings which requires resizing and some folks want the short snout on the end for use with the older type belt drive pulley set up and early crossmembers. I've seen where a 255 crankshaft was modified to fit the last of the 21 studs(1938) with the block mounted water pumps but a lot of work had to be done to the crank and block to do that. The crank journals were ground to the 1.999" dimension and the counterweights were cut down to clear the block. The earlier 21A con rods had to be used as well. They cut the snout down and also cut a new key way. A lot of machine work but it can be done. The block was bored to fit 3/16" thick sleeves with a 3 3/16" bore. This cut through to the water jackets in places so they used JB Weld to seal them at the top and bottom. It ran and finished the Great American Race and is still functional the last time I heard tell.

[Russ/40]

Always use the mains that are native to the block, not the crank.

[Bored&Stroked]

I've built many 59X engines with 8CM cranks (the 4" stroke Merc version). There should be absolutely no issue, other than if you happened to have a 3 1/16 bore 221 replacement version of the 59 series, then the late rods won't fit through the bores. You will use the main bearings designed for the 59X block and the rod bearings from the 8BA series. Again, you'll need to change the crankshaft timing gear - the thrust is wrong.

[weldor2]

so it's not really the crank, it's the bore size.

I have a 59x block bored to 3 3/16 so I think this will work

[Mr 42]

Thank's
I will give it a try, but its a bit down in the project plan.
So don't hold your breath ;-)

[Andy]

Easy swap. I put a 51 Merc crank in my 59A block. Just buy bearings for the 59A block. The first and secomd mains ar the same for both blocks. Just the rear main need to be 59A. I used the 8BA rods because of the easier cheaper bearings. I have an extra upper rear seal holder if you need it.

[Mac VP]

The 59 type blocks would ordinarily already have the correct upper and lower rear seal retainers that are needed to fit the rope seals at the rear of the motor. If they are damaged or missing we now have both types in stock.