Small Block Crankshaft ID

[condor74]

I was recently given a crankshaft that came out of a 318. I do not believe it was the original one to the engine. The engine was given to my machinist and he took it apart. The motor was rebuilt but not very clean. The rods all have brand new pistons on them but they are dirty. The block doesnt look like anyone ever cleaned it. The Crank looks dirty as well.
Here is my question. The crankshaft is forged steel and has a pilot bushing in the back of it for a manual transmission. I have never heard of 318s ever coming with forged steel crankshafts. I know 273s did come with steel and of course 340s came with steel up till mid 72. I want to know if I have a 340 crank or how can I tell if it came out of a 273. I have owned 273s but dont have them anymore. There are no numbers on the crank. Any info would be helpful. The crank is .010 and .010. It looks like it will clean up good. It would be nice if it fits my 340 cause I have one that happens to just need a crank and 1 rod.

 

[Meep-Meep]

There was a 318 truck crank that was steel and it's supposed to be the best one available to use for high HP applications. It was referred to as the 318-3 crank. I have no idea if this crank is marked or has any special features that set it apart from the regular cranks. I believe 318-3 was cast on the block and that was the only clue. Seems to me I have seen early 318's with steel cranks but that goes back a ways so not 100% sure. I might have been looking at 273's for all I know. Also, early 318's have floating pins and the later ones (74 and up?) have 340 style rods and are pressed pins.

 

[condor74]

I saw the new pistons on the rods that came out of the motor and they are all press fit. My 340 was actually a 73 model that came with a cast crank and that funky balancer. It did have stock floating pistons though and I still have all of those and the rods. Unfortunately I did spin a bearing. (I lost a transmission during the 1 to 2 shift and shot the rpms from 6500 to as high as the tach would go which was past 8000) What I did many years ago when I was running that motor was install a 69 340 steel crankshaft. The pistons I bought for it were all stock cast pistons for the 1969 model year. That way i could hopefully be close to the 10 to 1 compression ratio of the 69 340. All I need is 1 rod and I could put this thing back together if the crank is the correct one.

 

[chignikred]

what is the diameter of the rear nub, on crank. This is the dim, of what t he flex plate would slip over. Also what is the i.d. , what the torqueconverter slips into dim. This will narrow down the year pre/post 67.

Cranks do have numbers cast/forged into a fillet weight, faint at t imes but there.

 

[condor74]

I dont know the exact size but it is the larger size one. The same as the newer crankshaft. I know the early model had a smaller centering hub on the end of the torque converter. This is the larger one so i would say it is 68 or newer. I will look again for a number on the crank tomarrow.