Over the last 4 years, I've been building a 327 to drop into my Camaro (took forever, formally a broke college kid.) Years ago, I called a machine shop that regrinds cranks and told them I needed a crank. They told me they had a forged crank they could grind for me as long as I gave them mine for core. So I picked up the crank and gave them mine as core. When I finally finished getting parts and had time to throw the motor together, a friend that was helping me said that it looked like a cast crank. The motor is already put back together but I've gotten really curious as to which it is. It doesn't really matter since it is a daily driver, but it would be nice to know if I could safely really crank up the RPMs. I do have pics from when I was assembling the motor, can someone help me figure it out? Thanks in advance!!

 

Can't tell from those pictures.

Forged crankshafts are easily identified vs cast because a forged crank will have a wide parting line running down the length of the crank, while the cast crank has a thin parting line.

What's the casting number on the crankshaft? That can be easily looked up to tell you what the crank is.

 

Is this what you're talking about? Sorry for my ignorance, it's my first top to bottom rebuild. Motor is already together so looking up the number would be difficult

 

Yes, that's the parting line. Looks like a narrow line ie: cast crank.

 

Well, thanks for the help. I wish I would have known how to tell the difference when I picked this crank up. I remember when I called the place, they said they would have a crank ground in about a week. A week later I called to ask if it was done. The guy said to me, "Well, I had one almost done for you and then I remembered the 327s came with a forged crank and you should put back in what you originally had. So, give me a few days and I'll get a forged one done for you." I guess I learned my lesson to take 4 years to finish a project since it would be pointless to go back and complain now. But, like I said, it will be a daily driver so it's not that big of a deal.
So with all that aside, I'd like to eventually get the car on a dyno. What would be the "safest" RPM to take this motor to? I know there is more to it than just the crank, but I've heard people say that you shouldn't go over 5k with a cast crank. But I've also read on boards like this is it is okay to go over 5k RPMs, just not for long periods of time, like for drag racing and things like that.
Sorry if I sound a bit cautious, but I'd hate to blow this thing up after spending so much time and money on it.

 

I've spun a cast crank over 7000 rpm many times. Just stay away from excessive power adders.

 

Ok thanks! As for excessive power adders, I'm leaving it all motor, unless I can come across something that was the right price. I have too many other needs for the car before I'd look in that direction (Posi rear end with disk brakes, possible t-56 swap, build a cowl hood, body work, paint.) Besides, high 300's for HP should be good for now, hopefully. Not sure exactly what it'll have but it has domed pistons, 2.02" heads with 64 cc combustion chambers, cam specs of the '70s LT1, Edelbrock performer EPS intake, and Edelbrock 1405. I'm guessing the 600 cfm carb is a bit too small, but it's what I have for now. I'd like to swap to a Holley 750 DP when I have the funds.

 

That is a forged crank.

The parting line on a cast crank is paper thin. Night & day difference between them.

RBob.

 

...Do we have a deciding vote?!?!
I guess I can see how the machine shop might mistake it for forged and how my friend said it was cast!

 

Forged for sure

 

What the casting line looks like on a couple of forged cranks I have sitting in the shop......

 

Thanks for the pics, most of them I've seen online are SUPER hard to see the differences!