Are Cobra cranks really worth the risk?

[raredesign]

I know there are many fans of the cobra cranks, and for good reason, however unless you land a shiny new or barely used one, is it really worth the headache for a high horsepower build?

Based on what I’ve read, to handle high hp (~1000), they should be professionally heat treated, shot-peened, and rebalanced. The problem is that a used one you buy on eBay, etc may have been balanced multiple times or very poorly, and the journals may also be heavily worn.

Alternatively, Manley cranks look to have a reputation of 1400rwhp support, and can be purchased in a complete rotating assembly fully balanced from varying companies.

Again, the concern is high hp, and I am sure there are plenty that have successfully tossed a used one into a ~600hp build.

So, is it still worth all the extra risk and money to get a cobra crank?

 

[stv_huff]

This is an uneducated opinion but I do not see any reason to go with the used crank from a cost perspective. If you're spending that much money on building a motor isn't it preferable to buy a known good crank for piece of mind?

 

[01yellerCobra]

Guess it depends on how much the used crank is. And like anything else check over what you're buying. I know a couple Cobra engines making around 800 at the wheel. The only thing done to the crank was balancing for the new pistons.

As for needing all the special stuff to handle big power, you might want to consider the engines that are around 1000hp and never had a valve cover off. Although I do think a lot of that is because they're turbo cars.

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[tjm73]

Used parts come down to "cost/provenance/intended use" ratio for me. If I know it's history and the price is right, I am ok with it. If the cost is right and I don't know it's history and it's not a critical part, I am ok with it. If it's a crucial part and I don't know it's history no cost is probably low enough. Unless I can get it checked out first.

For a crank I would only buy a used crank from something I personally knew the history of, or if it had been checked for all dimensions by a third party machine shop.

 

[raredesign]

Thanks for the thoughts. I am leaning toward buying new. The thought of getting a used cobra crank wasn’t for saving money, but was only because some had recommended it as the superior option. I know the cobra cranks have a good reputation, but it looks like a Manley crank might be my best bet anyway. Regarding that, based on some other discussions, I am considering going stock stroke rather than stroker for the turbo build. I need to make a decision quickly to get in line for the motor work though.

 

[01yellerCobra]

I can't remember if Lunati or Manley bought the rights for the crank from Kellog. I could be thinking about the stroker crank too.

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[702GT]

Anybody killed a stock crank yet?

 

[JeremyH]

Not that I know of, something always else breaks first. I did sell the forged steel cobra crank that I bought and put my cast steel stock crank back in after comparing them when I built the motor back in 2010. I felt it was plenty adequate for my goals with car. You will actually find more issues online with the forged cranks after doing some searching since they are often used in most high hp builds. Most of what I find is broken snouts on forged cranks with belt driven setups though. So it is what is. If 99 guys use a forged crank for every 1 guy that uses a cast crank, the odds of seeing a failure lean towards a forged one.