Steel vs Cast crank........ please help.

[Tarrbabe]

I had my 340 crank reground about 2 years ago and got it back in a plastic bag. I got it out tonight and was shocked. I don't think this the crank I took in. I even ask the guy doing the work to be sure it was a steel crank and he said it was. This looks like a cast crank to me!
Can anyone tell me exactly what to look for? I don't want to accuse him of switching cranks without something to be sure about it.
I already have my new pistons, rings and have the rods in the same shop to be redone. He already bored my block so I owe him several hundred now but I can't accept it if he screwed me.
Please help.
Thanks.

[perfmachst]

hello, there is a parting line runs the length of the crank. on a forged crank it will be wide, on a cast crank, it will be a very narrow line. I always stamp my name on the front C/W. always stamp your stuff before taking it to machine shop. that way, no mistake about if it's yours or someone elses,.

[ehostler]

Great suggestion. I'll have to keep theat in mind, when I go to rebuild my engine.

[Duster_340]

Are you sure you took a forged crank to the shop? Forged till 1972 only i think.
The cast crank is still fine to use.

[Tarrbabe]

I ask the owner the day I took it in if it was steel and he said it was. But I doubt he would remember it now. Even if he remembered, he might not admit it because that would mean he would have to do something about it. He may not of been directly guilty, it could have been an employee. I think I'm screwed and still want a steel crank to go with my New Ross pistons ( 514 grams ) as I planned to rev this motor.

Do the cast cranks have the same harmonic balancer?

[Duster_340]

The balancers are different-do you have the balancer for the crank you took in?

[Tarrbabe]

It looks just like a 318 balancer.
My crank doesn't appear to have any parting lines on it. Maybe I'm crazy but it just doesn't look the same.

[pishta]

steel crank will have a bell like ring to it, cast crank wont, you have to have the two together for this test though. Steels are lighter in color also. Parting lines are the real deal, very narrow on a cast crank. 340 will have lightening holes in the throws to compensate for the heavier rods used.

[Tarrbabe]

so it's a 340 crank I guess. Three of the throws have no noticable lines. One does and it appears to be maybe close to an inch wide.

[Ray Bell]

Originally posted by Duster_340
The balancers are different - do you have the balancer for the crank you took in?

Tarrbabe... take particular note of this question...

It gets to the root of the issue and is your proof if it's needed.

[Ray Bell]

Originally posted by ehostler
Great suggestion. I'll have to keep theat in mind, when I go to rebuild my engine.

Indeed, a very good suggestion.

[Tarrbabe]

I've got some research to do.

I really like the idea of marking everything BEFORE you take it to the machine shop. Need to get me a die set

[bbeckwith]

saved this picture for just such an occasion.

[John Kunkel]

Crank comparison:

[Ray Bell]

Originally posted by Tarrbabe
.....I really like the idea of marking everything BEFORE you take it to the machine shop. Need to get me a die set

I'd say it would be a good idea that your markings aren't that obvious and that they're not as repeatable as they might be with a number/letter punch set.

Maybe get a letter punch with your initial and disfigure it so it's a totally unique figure?

Good piccies there, bb and kunkel. Very helpful.

[Tarrbabe]

I need to take percautions from now on.
Three throws on my crank have NO parting lines. One has one about 1 inch wide but even it is very hard to distinguish. I guess cast cranks all have the sharp parting line on them? Some of the edges on the crank are rolled and the oppisite side is sharp. This is mistifying. Maybe it is a steel crank but I still don't remember it looking like this. Especially the big sawed place down one of the counter weights.

[Ray Bell]

Do you think you could show us a photo of yours?

[hellhound]

Originally Posted by perfmachst

hello, there is a parting line runs the length of the crank. on a forged crank it will be wide, on a cast crank, it will be a very narrow line. I always stamp my name on the front C/W. always stamp your stuff before taking it to machine shop. that way, no mistake about if it's yours or someone elses,.

Man thats good advise... I have a side project that Ill be starting on soon...there is no way I want someone stealling my 3.76 forged BB crank... More on this project coming soon

[Aspenj2002]

You guys need reputable machinists in your area huh? I know I wouldn't have the huevos to switch someones crank.

[perfmachst]

hello, as a side note, all engine parts left at my shop, are stamped as the customer watches.therefore, no mix ups. because all 440 or 360 blocks look alike. same with heads, cranks. just food for thought.

[jelsr]

At the risk of repeating others, the cast crank is neat and tidy with sharp edges. Steel cranks on the other hand look like they were done with a chain saw! Some edges are rounded on one side, the front and rear throws where the lightening holes are sometimes have goobers sticking out around the hole, etc. Unless someone has spent a great deal of time smoothing them up steel cranks are not a thing of beauty.

[Ray Bell]

I'll get some pictures when I get a chance... but here's a Poly 318 crank to start it all on the way... not mine, but a guy from the 318Poly group's... what a surprise he got when he opened this up!

[bbeckwith]

Tarrbabe, another way to tell if it's forged, stand it on end, and tap the end with a ball peen hammer, it should ring if it's forged. Sorta like a crystal glass will vibrate at the right sound frequency, or a bell ringing. Just dont go smashing the crank with the ball peen, just a light tap will do.

[jelsr]

If you do the sound test remove the bolt and washer that retain the damper. With that big flat washer sitting on the top not tightened it will dampen the ring and make it sound flat like a cast crank.

[Ray Bell]

And if it's cracked?

I recall reading once that a guy retired from a job on the railways, I think it was in England. His job for many years had been to hit wheels on steam locomotives with a hammer. He didn't know why he was doing it... or so the story goes.

Of course, it was to see if the wheel had developed a crack.