340 Crankshaft bit the dust

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char69ger

char69ger

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Tore down an old 340 and the crank is messed up pretty bad. It had already been turned 30 over on the mains and 10 on the rods. I'm going to order a new stock stroke crank from Summit.
I will be using the same pistons and rods that were in the motor. This is not going to be a performance build, just trying to rebuild a stock type motor for dependability.

Here is a quote from the Summit website "The Eagle Specialty Products 103403310 is internally balanced for non-weighted balancer and flexplate/flywheel."

Does this mean I can just put it in the motor without a trip to the machine shop?

Thanks
 
It means its internally balanced like the 68-71 340 forged cranks were. 72-73 were cast and externally balanced with a special weighted balancer and flywheel. Not sure about the flex plate.

I would have it balanced.

What year is your 340?
 
NO! DO NOT JUST PUT IT IN!!
You'll have to get the assembly balanced. It's a replacement crank and the balance job from the factory will not be even close.
 
Me personally I would source a stock replacement be it cast or forged depending on what I took out, and I would still have it balanced.
 
yellow rose said:
It's not a hundred dollars if he has to buy Pistons.
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Why wouldn't the stroker crank work with the pistons he's got?

As much as this crank has been machined allready , I would be surprised if he had stock pistons in there to begin with
 
diymirage said:
Why wouldn't the stroker crank work with the pistons he's got?

As much as this crank has been machined allready , I would be surprised if he had stock pistons in there to begin with
Click to expand...

He'd need idk a .300" head gasket? lol
 
dano said:
It means its internally balanced like the 68-71 340 forged cranks were. 72-73 were cast and externally balanced with a special weighted balancer and flywheel. Not sure about the flex plate.

I would have it balanced.

What year is your 340?
Click to expand...
It is a 68.
 
diymirage said:
Why wouldn't the stroker crank work with the pistons he's got?

As much as this crank has been machined allready , I would be surprised if he had stock pistons in there to begin with
Click to expand...

Put down the computer and walk away.
 
MopaR&D said:
He'd need idk a .300" head gasket? lol
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Now that you mention it, that makes perfect sense
Not sure why that escaped me before...I guess if a crank is all that is needed he should probably disregard what I said before
(And perhaps what I'm gonna say tomorrow)
 
All it means when it said it's internally balanced is, it's neutral balanced, for an engine that's balanced in that way. That does not mean it's balanced for your particular engine. There's no way in the world I would buy a crank and not have it balanced, because there's no way in the world the crank company can know all of the weights of all the parts in any given engine. Plus, what if your engine has been balanced before? What then? You could "just throw it in" and end up shaking your teeth out. Why chance it? I consider it part of the replacement process. It's incomplete without it. If you need to cut that corner, then you should be building Revel models, instead of real cars. Just save up if you need to, but do it right.
 
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You might call Eagle and ask what the bobweight is on the crankshaft....that is the weight that crankshafts need to be to balance your rotating assembly...also the the Eagle cranks required narrowed bearing on the crank and rods...

Summit has it for 750 dollars plus another 200 bucks for bearing...I would be looking for a used forge crank...lol
 
Char 69; If your engine was a virgin, it would be OK to replace the crankshaft without balancing IF the crank was balanced to factory specs. Since your engine has been apart, it would be a gamble to not balance it unless your rod and piston assy weights can be verified. The factory service manual for your engine will have these specs.
 
If that part number is for an eagle cast crankshaft i hope they are better than their cast stroker crankshafts. I have seen several of those in two pieces on engines that werent big horsepower combos.
I would use a factory cast crankshaft over a cast eagle crank any day.
 
Eagle would be my last choice. Get a forged 318 or 340 factory crank. Mopar metallurgy betwas wayter than the alternative.
 
I have no problem getting it balanced. Was just unclear what the statement meant.
I also looked for a used factory crank but have been unable to find one. Mopars are pretty scarce around here.
 
pt70 said:
Char 69; If your engine was a virgin, it would be OK to replace the crankshaft without balancing IF the crank was balanced to factory specs. Since your engine has been apart, it would be a gamble to not balance it unless your rod and piston assy weights can be verified. The factory service manual for your engine will have these specs.
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I agree 100%, the problem is, it's over 50 years old. No tellin what all's been done to it. That's a lot of money to spend to wind up with a pile of scrap metal in the end.
 
diymirage said:
Why wouldn't the stroker crank work with the pistons he's got?

As much as this crank has been machined allready , I would be surprised if he had stock pistons in there to begin with
Click to expand...

If you don't know the answer to that question, please go back to school and learn to read
 
JBurch said:
If you don't know the answer to that question, please go back to school and learn to read
Click to expand...

it all clicked when @MopaR&D mentioned the head gasket yesterday
im not sure why it didn't dawn on me sooner, I guess sometimes the obvious is the easiest to overlook
 
If its the original crank to the block, I'd be concerned at to why is .030 over all ready. What did the main bearings look like?
 
If you end up going cast crank avoid Eagle. I would buy Scat if cast. At your HP probably not an issue but for the same money why chance it.
 
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