340 Crankshaft bit the dust

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Let me jump in
No way would I buy another Eagle crank EVER
just saw what furry said and I agree
I'd rather have a cast scat
and yes I'd go stroker kit
If you are just doing a stock rebuild and have it apart there are bearings, rings, timing chain gasket choices
check the bores
 
Can you show us the main and upper rod bearings? Or did you chuck them?
Look at the main saddles, the oil feed to them at the cam feed intersection, see how the bearings line up.
 
Wyrmrider said:
Let me jump in
No way would I buy another Eagle crank EVER
just saw what furry said and I agree
I'd rather have a cast scat
and yes I'd go stroker kit
If you are just doing a stock rebuild and have it apart there are bearings, rings, timing chain gasket choices
check the bores
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before you jump in...LOL>..take a look at what scat has to offer....they have no 3.31 stroke crankshaft listed....
 
OK here is the whole story. I bought the car in 2016 after a big flood here. The car had gone under completely. I drained the oil and water from the motor and flushed it with marvel mystery oil a couple of time. I then put fresh oil and pulled the distributor gear and turned the pump with a drill for a few minutes. I drained and did it a couple more times changing the filter also. I fired the motor and have been driving it sparingly for the last couple years with no issues. I want to drive it more often so I decided to pull the drivetrain and inspect it. That's when I found the crank problem.
 
all the more reason to get a stroker kit
Eagles break
reminds me of the PAW days
PAW crank grinders were on an incentive bonus system
so they cranked up their steady rests, increased the pressure and ground as fast as they could
of course they bent the cranks
We reground many many cranks, many had to go way under to fix
 
The Eagle bobweight is 2050 for both cast and forged, designed to be heavy out of the box so you would have to remove weight in most cases instead of adding tungsten. The Eagle cast crank has .092 fillets and the forged has .125 fillets. I bought standard bearings before I bought the forged crank and had to chamfer the edges of the bearings to fit the crank.
 
pishta said:
The Eagle bobweight is 2050 for both cast and forged, designed to be heavy out of the box so you would have to remove weight in most cases instead of adding tungsten. The Eagle cast crank has .092 fillets and the forged has .125 fillets. I bought standard bearings before I bought the forged crank and had to chamfer the edges of the bearings to fit the crank.
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Buy h series and you dont have to.
 
pishta said:
H series were ~$88...King SI standards were $37, worth it to me to hit them with a dremel and clearance them myself. I thought about it until I saw the H series price.
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Yep, between Main and rods... 180.00ish
If you make a clamp jig and/or have a decent belt/wheel sander....its easier to mod the bearings...but full groove main are where it's at.. depending on clearances. Just slot oil the feed holes on 1-4 main bearings..
 
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The OP's proposed Eagle crank is going to be difficult to balance with stock rods and pistons, if not almost impossible. It is designed for a target bobweight of 2050 grams as Pishta said. (Numbers are right out of their catalog.) The stock 340 rods and pistons have a bobweight of around 2310 grams. It is going to take a LOT of weight added to any Eagle crank to make it balance out with the stock rods and pistons. It is a 100% non-starter approach in my book.

A stock early 340 crank is going to be stronger and cheaper to use. Shop around $100-150 for a 340 crank is not unusual.

BTW, 2050 grams is a lighter bobweight than any of the stock 340/318/273 setups from the factory by anywhere from 70 to 260 grams. So these Eagle cranks won't balance with any stock LA piston&rod setups without adding weight.
 
Thanks for the bobweight values. Another variable is the weight of the Eagle rods. The H-beam rods are heavier than the I-beam rods.
I don't understand why the manufacturers don't make .040 or .060 undersize bearings. Which would be less than a 5% loss of strength of the crankshaft. With the quality of the old Chrysler steel, they'd still be stronger than some of the new stuff.
 
JBurch said:
If you don't know the answer to that question, please go back to school and learn to read
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In his defense, there are some builds that use the same pistons, all depending on the stroke and rod length. I can think of several big block builds for instance, that are like that. Sorta akin to the slant sixes. They all three used the same exact pistons, but varied the stroke and rod lengths to make things fit.
 
RustyRatRod said:
In his defense, there are some builds that use the same pistons, all depending on the stroke and rod length. I can think of several big block builds for instance, that are like that. Sorta akin to the slant sixes. They all three used the same exact pistons, but varied the stroke and rod lengths to make things fit.
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Yes triple r you have a point there with the /6's; name me a combination used in a small block............
 
JBurch said:
Yes triple r you have a point there with the /6's; name me a combination used in a small block............
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Ok. The Tom Hoover 360 used 340 pistons. There's one. I'm not gonna spend all day on it, but I bet there's at least one more.
 
RustyRatRod said:
Ok. The Tom Hoover 360 used 340 pistons. There's one. I'm not gonna spend all day on it, but I bet there's at least one more.
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OK, but it sticks .060 out of the hole for starters, from my frame of reference never that popular
 
JBurch said:
OK, but it sticks .060 out of the hole for starters, from my frame of reference never that popular
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I don't disagree. You said name one for a small block dangit. I did. LOL Don't be a democrat and change the rules now. LMAO
 
pt70 said:
Thanks for the bobweight values. Another variable is the weight of the Eagle rods. The H-beam rods are heavier than the I-beam rods.
I don't understand why the manufacturers don't make .040 or .060 undersize bearings. Which would be less than a 5% loss of strength of the crankshaft. With the quality of the old Chrysler steel, they'd still be stronger than some of the new stuff.
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One reason is because most guys think a .020 under crank is junk. It's not, but that's the case. A .025 under SBM Rod journal is a standard large journal SBC Rod journal. I never build any SBM Stroker without using SBC LJ Rod size. That means taking a brand new crank and turning it .025 under just to start. Now you can buy Chrysler cranks with SBC sized journals so you don't have to do that. Early on, that's what you ad to do.


The other issue was way back when the under sized bearings all had the same thickness of shell. Which meant that as the Rod journal gets smaller, the overlay had to get thicker. Once the overlay got to maybe .030 or so, depending on journal diameter, you'd get overlay migration, flaking and other issues like that.

Since the mid 1980's (maybe before but it's hard to track down the history) the bearing manufacturers started using thicker steel shells so the overlay stays the same thickness regardless of undersize. So that did away with overlay migration etc.

But it didn't matter as old issues die hard and most guys won't go that far under. I have a crank out in the shop that was turned down to SBC SJ Rod throws. So they measure 2.000 and that's .125 off the throw.

I realize that we are discussing two things at the same time, in undersize bearings and undersized Rod throws, but they go together. They go together because both are part of the issue. Some guys think the throws get too small and others think the thick bearings are bad.

Either way, you can go way undersized and not hurt a thing. Getting bearings for and undersize that far is an issue. That's why it's better sometimes just to change the rods out to Chevy throws and be done with it.
 
What actually happens when u turn the journal down is that the bearing speed actually slows down putting less stress on the crank. I have had big block cranks turned .060. It is hard to find a bearing more than .030. U can offset grind the crank to gain more compression on low compression motors. Kim
 
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Newbie crank question but didn't factory cranks have surface hardening on the journals which would get removed if the journals were ground undersized? Or was that just 426 Hemi crankshafts or something?
 
Most were not hardened
and factory cranks had high pressure rolled filets not big radius
the pressure compresses the metal down giving an excellent crank without the need for chamfering the bearings or grinding away the filet with a regrind
not to worry
works good
hmmmm use chevy bearings and adjust the stroke,
chevy size rods are easier to clear with big strokers
for whoever posted above
the 340 pistons to start with on that build are the low compression ones
you can also mill half off and try and get some quench
watch your PV clerance
 
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
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Wrist pin height needs to be different on a stroker crank.
 
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