Crank Thrusting Foreward Issues
- Thread starter T56MaxTorq
- Start date
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I found this old thread that you were part of over 6 years ago that pretty much covers this subject.
318 v 340 Crankshaft
318 v 340 Crankshaft
good thread
Thanks
What i don't know for sure and can't get anyone to agree or disagree is......Is the 340 cast crank internal or external balance.
You know, it don't really matter. if you're going to us a 340 crank (cast or forged!) you will need to balance the assembly, because the 318 counterweights and pistons are lighter.
So to the Op. If you don't want to balance your rotating assembly, you need a 318 crank!
yellow rose
Overnight Sensation
A 340 cast crank is externally balanced.
THANK YOU.
I just wasn't 100% sure.
nm9stheham
Well-Known Member
FWIW..... You would be able to balance 318 rods and pistons with the 340 forged crank, even with the later, heavier 318 rods. The 340 pins and pistons are so much heavier than the 273/318 pins/pistons: the 340 bobweight is around 2326 grams, and the 318 (heavy rod) bobweight is around 2173 grams. So weight will go off.
I would also expect that the 340 cast crank would also balance out with the 318 parts, using the 318 neutral balanced damper and TC, but I have some data to gather to be sure that is the case. Keep in mind that 'external balanced' does not mean that all the counterbalance is external; actually, just a small part of the counterweights at each end of the crank is located externally. So since less total counterweight is needed with lighter rods/pistons/pins, it can be removed from the external parts first, and if enough is removed, then all of the external counterweighting can dissappear.
I would also expect that the 340 cast crank would also balance out with the 318 parts, using the 318 neutral balanced damper and TC, but I have some data to gather to be sure that is the case. Keep in mind that 'external balanced' does not mean that all the counterbalance is external; actually, just a small part of the counterweights at each end of the crank is located externally. So since less total counterweight is needed with lighter rods/pistons/pins, it can be removed from the external parts first, and if enough is removed, then all of the external counterweighting can dissappear.
Daves69
Well-Known Member
Or they may have had it in and during assembly tilted the trans enough to allow the converter to slide forward.
A small C-clamp or homemade "Z" shaped stop that can bolt to the inspection cover boss might be a worthwhile tool to avoid this.
TrailBeast
AKA Mopars4us on Youtube
As much experience with engines and dyno's that you apparently have is probably about equal to what I have in transmissions.
Where's all the metal from wearing that thrust and bearing like that?
How could that much of a new #3 bearing thrust surface still be there with that much wear on the crank.
How could the pump not be engaged for so long as to wear the crank like that and have the trans still drive? (Impossible)
He put it together right and the trans is fine. (as long as there wasn't and old pilot bearing the crank register from a past stick shift)
It just got the surface overlooked on assy.
That's my warrantee decision and I'm sticking to it.
OH, and you can get a brand new crank from Autozone for right at 200.
Less for a reground used.
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Daves69
Well-Known Member
An article that may be of use............
Thrust bearing failures
Thrust bearing failures
T56MaxTorq
Well-Known Member
Thanks for the info guys, lots of good stuff. I have a feeling the trans went in a little goofy and damaged the crank. I may have felt the trans in a goofy spot and corrected it but the damage had been done. hard to say since it was so long ago. I'm gonna grab a different 318 mag crank and huck this one, they're plentiful enough. Add some new bearings, do some oiling mods and get back on the road. I'm secretly excited to see what condition the oem pistons are in after adding that much boost.
Phil
Phil
Question, have you pulled the trans out and looked for the front pump ears on the pump gear? It has been said above and I'll say it again, there is no way those pump tangs or ears are stout enough to as to push the crank forward enough to cause that damage! No way! To give you an example of how fragile they are. I was installing the 727 trans back in my Dart and I was having a lot of trouble getting the convertor to engage with the pump! I finally got the convertor to slide in far enough(just by hand) to install it. Guess what the trans didn't work! Just by me sliding the convertor in and out and rotating it, I broke the damn tangs off the front pump gear.
I don't say this to cause a pissing match with you, but rather instill in your mind to LOOK else where for a cause.
yellow rose
Overnight Sensation
As much experience with engines and dyno's that you apparently have is probably about equal to what I have in transmissions.
Where's all the metal from wearing that thrust and bearing like that?
How could that much of a new #3 bearing thrust surface still be there with that much wear on the crank.
How could the pump not be engaged for so long as to wear the crank like that and have the trans still drive? (Impossible)
He put it together right and the trans is fine. (as long as there wasn't and old pilot bearing the crank register from a past stick shift)
It just got the surface overlooked on assy.
That's my warrantee decision and I'm sticking to it.
OH, and you can get a brand new crank from Autozone for right at 200.
Less for a reground used.
What I have seen happen is really simple. The converter is not fully into the pump. The Texans is bolted to the block and the converter is very close to the flex plate. Close enough to bolt the converter on.
And there you have it. It don't matter what you use for assembly lube, how well everything is machined or what bearing you have. Any, and it don't take much to mean any, force against the thrust bearing when the engine fires and it is over. The load from the crank smears the bearing and it's over. Now the long slow process of adding wear begins. You don't instantly get .100 wear. It takes time.
That's what happened to the OP. And more than likely, once the engine fired, the converter slid back into the tangs and he got lucky and didn't kill the pump. Most of the time it kills the pump. Maybe the OP got lucky.
Call any bearing manufacturer and ask about thrust failures. They will tell you the same. Most of the time it comes from improper torque converter installation.
T56MaxTorq
Well-Known Member
After cutting the oil filter open, it was trashed with crank and bearing bits. Found the 1st oil filter I ran it with (before the trans needed to come out for repair) and it didn't have much of anything in it besides some dog hair and a little white lithium. It only ran for about an hour with that filter. I guess it's safe to say the second trans install is what did her in.
yellow rose
Overnight Sensation
A win for the chicken dinner.
Bummer though. I hate to see tore up ****. We all learn faster the hard way.
T56MaxTorq
Well-Known Member
Yeah it sucks but that's the game. I'd rather be spending money on traction and tire. But I needed to do some little things like wrap the hot pipes, secure some fluid lines differenty, seal off the firewall, so it's not all bad.
moper
Well-Known Member
No, you misunderstand me... I have broken tiny bits off before in hard-to-reach spots... it sucks.
nm9stheham
Well-Known Member
I was not sure..... yes, that is bad juju.....
racerhog
RacerHog likes his Mopars
Check the torque converter for ballooning..... Or it has a bad stater support.. But i'll bet it has a defective converter in it... That should fix the issue...
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