[Bblock007]

Hi,
What can you tell me about these cranks?? I have a 1970 Camaro SS L-34 402 and I am trying to verify what the factory crank in these motors was. My block is a CTX. In the book "Chevrolet by the numbers 70-75" there is a section about the 70-72 402 cranks, I will post the pic rather than type it out. Is there a crank with the 3rd lobe 7/16" wide if so, what cast number is it? I saw you comment something about 7/16". Look forward to hearing what you have seen.

Seems that because I'm new they won't allow me to post a pic attachment. What it says in the books is

"The 402 crankshaft is basically the same as the 427 crankshaft used from 1966-69, except that the 402 crank is lighter, due to a different counterweight design. To tell, check the width of the third counterweight. On a 402 crank it should be 7/16" wide. You cannot tell a 402 crankshaft from a 427 crank from the shape of the flywheel flange since they are the same. Some 402 crankshafts in low-horsepower applications may be cast iron."

Is this true, 7/16"? Or is that a typo and it should be 3/4"? How wide is a 427?? I saw someone say 7/8" wide but I don't know how that would fit in a 402 block, it looks like it would hit the block and/or the rods.

Does anyone know about the other cast numbers I put a red dot next to, along with the 6223?

Thanks,
Todd

 

[cheveslakr]

I believe the accepted applications are the 6223 forged crank in the L34 and L78 396 engines, and also the 427s except the L88, which received the 7115 forged crank which has a 3/4" counter weight.

 

[Saltherring]

You probably have more information than I do on the 1970 model year, given I only have the '65'-69 Chevrolet by the Numbers book. I have a 7115 L88 427 crank on a workbench but I believe when I measured the 3rd counterweight it was 3/4", same as the 396 6223 forged cranks. I can check tomorrow if you want. I do know that ALL '65-'67 Chevy Mark IV engines came with forged steel crankshafts. Beginning in 1968 L35 engines came equipped with Nodular Iron (cast) cranks, while L34 and L78 retained their forged cranks. All 427 engines came with forged cranks. I believe the L35 engine went away in 1970, replaced by the LS3, which in all likelihood had a cast crank like its predecessor, the L35. The L34 became the standard engine for the SS 396 Chevelle in 1970, with the L78 being available until November of 1969, when it was replaced by the LS6 454. I believe all 1970 454 engines had forged cranks too. Not sure after that. Another note: Crankshafts in all "Special High Performance" MK IV engines (396/375 HP, 427/425, 430, 435 HP and 454/450 HP) were "Tufftrided" and had cross-drilled main bearing journals.

Oh, and welcome to Team Chevelle.

 

[Bblock007]

Thanks for the welcome! Sorry, I crossed platforms but I know Camaros and Chevelle shared some items and thought I'd expand the info base. Yeah, if you wouldn't mind checking that would be appreciated. Have you ever heard of a 7/16" 3rd counter weight lobe? And when you guys say 396 you do mean the 402? Because that is the year I am wondering if the 70-72 402 cranks were special or if the book had a typo. I assume everyone knows in 70 GM opened the bore 0.030" to 4.126".

 

[Aaron]

Do you have just a block and are needing a specific crank? Your doing a numbers matching restoration?

According to what I have.

396 counterweights are 3/4" wide.

402 counterweights are 7/16" wide.

427 counterweights are 7/8" wide.

Steel cranks will have a higher pitch sound if you tap it with a metal punch or wrench.

Cast cranks have a thin parting line.

Here is team chevelle thread.

How do you identify a 366, 396, or 427 steel Crank | Team Chevelle (chevelles.com)

 

[Saltherring]

I have an early appointment this morning and will be unable to get to the shop to measure the third counterweight on the L88 crank I have. I, however, am 99% certain it measured 3/4" when I measured it awhile back.

This crank was removed from a service replacement L88 short block that had been purchased from Chevrolet by WVA racer Jim Minnick in the mid 1970's. Minnick etched a counterweight of that crank with his name and a date in November 1976 as I recall.

In the early 1990's Minnick removed the crank from the L88 short block and sold it to his friend "Joe" so he could rebuild the "numbers matching" short block in his 1969 L78 SS Chevelle. I bought that car in 2016 and removed and replaced the engine with another JD-coded block. I then ratholed the "numbers" block and that standard/standard L88 7115 crankshaft. I would sell that crankshaft if anyone is interested.

 

[Bblock007]

Well, I am trying to confirm the 7/16" for the 402. Is that true? Has anyone been able to confirm that? Can someone send me a picture of the 7/16" factory crank. Yes I would like to do a number matching restoration.

 

[Aaron]

Well, I am trying to confirm the 7/16" for the 402. Is that true? Has anyone been able to confirm that? Can someone send me a picture of the 7/16" factory crank. Yes I would like to do a number matching restoration.

That is pretty much what I know. Read my link.

 

[Bblock007]

Thanks Aaron. I read your comment and read your link to 'how to identify a 366 396 427 crank'. I had read that post before and thanks for posting. You said 'according to what you have', are you saying the knowledge you have is from that link or do you have a 402 - 7/16" lobe crank? Do you have or seen one? If you have one, is it for sale? I have read that but want to confirm and find a original. Thanks.

 

[Aaron]

Thanks Aaron. I read your comment and read your link to 'how to identify a 366 396 427 crank'. I had read that post before and thanks for posting. You said 'according to what you have', are you saying the knowledge you have is from that link or do you have a 402 - 7/16" lobe crank? Do you have or seen one? If you have one, is it for sale? I have read that but want to confirm and find a original. Thanks.

No, I physically dont have one. All my information is print. I have not actually measured any of those.

Welcome. I might could help you locate someone who would have one.

 

[Bblock007]

No, I physically dont have one. All my information is print. I have not actually measured any of those.

Welcome. I might could help you locate someone who would have one.

Yes, please do! I would appreciate it.

 

[Saltherring]

I just now got home and went out to the shop and mic'ed the third counterweight on my L88 crank. It measured .752. This agrees with what Jerry (Cheveslakr) wrote also, that the third counterweight of a 7115 L88 crank should be 3/4" thick. I know for a fact this crank was removed from a factory replacement L88 427 short block.

 

[Bblock007]

Okay thank you Saltherring.
Appreciate it.