Small block crankshaft endplay

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Penstarpurist

Penstarpurist

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I know their are several threads asking the same question, and I am sure that I know the answer to this question. My son is working on his '71 Plymouth valiant, its a multi issued repair. His steering gear box leaks like a sive, so he's got firm feel building him a stage two unit, replacing the pump as well, new dual piston brakes, steering linkages, sway bar, etc. Well on top of that, the timing chain cover leaks heavily, so he pulled the radiator, belts, pulleys, etc. He asked me to look at how much crankshaft endplay he has front to back. Now the crankshaft dampener bolt is removed, but when you grab the balancer the entire crankshaft moves probably 1/2" front to back, you can see the torque converter through the starter opening and the only thing that stops the crankshaft travel is the torque converter hitting the back of the block or the converter hitting the timing cover. I told him that I cant remember ever seeing so much endplay. Now, maybe because the dampener bolt is removed its moving more than it should or normally would. But I think the fact that all the internals are still in there, that's excessive to say the least. But I told him that I would ask what the general consensus is. Original numbers engine, never been out of the car or rebuilt. I am thinking it's time for it to be rebuilt? What's the thoughts on this.
 
MOPAROFFICIAL said:
Thrust bearing is wasted.
Pull the motor
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That's what I was thinking as well. My son just didn't want to hear that from me. Lol, I can't blame him, but I told him that its a numbers matching 2 dr 71 valiant and the value is there to warrant doing it right. Of course to me, when it comes to doing something the right way, the cost is irrelevant. Cheaper always to do it right from the beginning, rather than halfway the first time just to have to do it right the second time through. Thanks for verifying what I thought.
 
Penstarpurist said:
That's what I was thinking as well. My son just didn't want to hear that from me. Lol, I can't blame him, but I told him that its a numbers matching 2 dr 71 valiant and the value is there to warrant doing it right. Of course to me, when it comes to doing something the right way, the cost is irrelevant. Cheaper always to do it right from the beginning, rather than halfway the first time just to have to do it right the second time through. Thanks for verifying what I thought.
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He's going to need to look close at the transmission too! Otherwise the next engine may suffer the same fate. I forget what causes it, but I had the same massive thrust bearing failure and it was explained to me how my auto trans was likely to blame. I've since gone four speed, so I didn't keep that knowledge in my head, sorry LOL.
 
Phreakish said:
He's going to need to look close at the transmission too! Otherwise the next engine may suffer the same fate. I forget what causes it, but I had the same massive thrust bearing failure and it was explained to me how my auto trans was likely to blame. I've since gone four speed, so I didn't keep that knowledge in my head, sorry LOL.
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I will definitely do some research on that part as well. Maybe time to rebuild the transmission as well too. Always better to err on the side of caution.
 
Phreakish said:
He's going to need to look close at the transmission too! Otherwise the next engine may suffer the same fate. I forget what causes it, but I had the same massive thrust bearing failure and it was explained to me how my auto trans was likely to blame. I've since gone four speed, so I didn't keep that knowledge in my head, sorry LOL.
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Actually 4 speed cars are harder on the thrust bearing. Kim
 
oldkimmer said:
Actually 4 speed cars are harder on the thrust bearing. Kim
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I believe that, but isn't there something to do with the torque converter or cooler which can cause excessive thrust force and wear? I just forget the details, but obviously a properly functioning auto shouldn't hurt the thrust..
 
At half an inch, it would have been making a lot of noise for a long long time. It was eating the rear cam boss the whole time, so you'll be looking at fixing that when the engine comes out. And Ima thinking the crank will be toast and maybe the bulkhead itself. When mine did that; I had just won a gate-prize of a 30gallon drum of ATF . After the oil was all gone,lol, I finally pulled the engine.
 
AJ/FormS said:
At half an inch, it would have been making a lot of noise for a long long time. It was eating the rear cam boss the whole time, so you'll be looking at fixing that when the engine comes out. And Ima thinking the crank will be toast and maybe the bulkhead itself. When mine did that; I had just won a gate-prize of a 30gallon drum of ATF . After the oil was all gone,lol, I finally pulled the engine.
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I think your right, for a long time it was making a noise, almost like a grinding/chaifing noise. Because it always had a steering pump and steering gearbox issue leaking heavily I think he chalked it up to being from there. But seeing now the endplay in the crank, I think it's what he was hearing. With the issues it had, it has been parked in the shop for the past six months or so, I think we just forgot about the noises until now.
 
I'm gonna go on record as saying there's no way to have 1/2" end play. The engine would stop running before that much metal could be worn away.

The auto trans pump cannot place any axial load (thrust) on the crank. There's is no reason for the pump gear to thrust - it's an even 'cut'. Even if it did, the drive tangs on the converter snout would simply compensate.
 
gregcon said:
I'm gonna go on record as saying there's no way to have 1/2" end play. The engine would stop running before that much metal could be worn away.

The auto trans pump cannot place any axial load (thrust) on the crank. There's is no reason for the pump gear to thrust - it's an even 'cut'. Even if it did, the drive tangs on the converter snout would simply compensate.
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I didn't put a tape measure to it yet, but will once we get it pulled out. But its definitely a large amount of movement. By eye it looks like it is a solid 1/4"-3/8" of an inch at least. It literally makes a clunking noise from moving it back and forth. And I am assuming that any amount you can physically see by eye is a good indicator that it's had the thrust bearing failure. I am just hoping that the block hasn't had any unrepairable damage, as I would think that a big part of the value of the car is in it's being an original drivetrain car.
 
Correct me if I'm wrong...but if there was that much end play it's gotta be eating the internals, right? I mean the crank can't move that much without trying to take the rods/pistons with it and putting weird side loads on things?
 
Exactly. When I pulled my 340 apart, the crank thrust surface was bad, and there were blue heat spots on the counterweights from rubbing the block
 
i had that problem on 2 77 360's Chrysler replaced the engines , blocks were toast , of course i drove the crap out of them for 10,000 miles before i brought them in . hope your block is in better shape than mine were .
 
Dang, this's not sounding promising. Lol. I guess the question comes down to: pull it out, disassemble it and take the block, crank and rods in to a machine shop with the expectation that its probably shot. Pull the engine, grab the 318 that we pulled out of a 71 dart that's got the exact same month and year date stamps from the factory and rebuild it to use. As we have an exact same year and month spare engine. Or put the '72 360 engine in it, great shape very low mileage engine. Or buy a crate engine, install and enjoy the reliability with a warranty.
 
No one alive who is a man cares if the date stamps are the same. The only people who care about date stamps are 'Ellen' watchers and Corvette owners

I'd pull the pan and look around before making any decision....but I'd plan on using a different engine, most likely.
 
First, I'd verify that the balancer is not moving on the crank. Re-install and tighten the balancer bolt to eliminate that possibility. If it then still has anything more than 1/16" of end play, the engine has to come apart. Hard to say what caused it. Lot's of possibilities including a ballooned torque converter (unlikely in a street car, but, I've seen it in race applications) or a burr on the cranks, faulty thrust bearing, bad machine work, etc.
 
gregcon said:
No one alive who is a man cares if the date stamps are the same. The only people who care about date stamps are 'Ellen' watchers and Corvette owners

I'd pull the pan and look around before making any decision....but I'd plan on using a different engine, most likely.
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Lol, I have never seen anything with Ellen, so I guess popping the oil pan and taking a look with the expectation of using a different engine is probably going to be the way to go. My son is heavily looking at the 360 we have sitting on an engine stand with a 727 transmission next to it. If we're going to replace the engine, may as well swap the 904 out for a 727 since we can. Would still regasket, bearings, cam swap the 360.
 
If you're going to just use the drivetrain as-is, sure, give the 727 a try. Personally, I'd rather keep the 904 and beef it up a bit along with getting the proper converter for the 360 and warming over the 360 a bit. That way, I'd save money on not having to get a new driveshaft and put that money toward the converter and engine mods. The 904 is a better performance and mileage transmission than the 727 (when built properly), and it's lighter to boot.
 
So put the bolt back in, still moves over 1/8" to 3/16". Time to pull the engine, drop the pan and see. It moves roughly about the same. It was late last night, covered in grease, so it probably looked like alot more at the time. But I'm guessing the end result is still the same. I measured the movement with a tape measure this time.
 
Yeah, that's way too much endplay, and the reason the timing cover seal is leaking. More than likely, the crank will have a bad groove cut into it by the thrust bearing. Probably cheaper to just get another crank, but, it can be welded and reused if necessary. Hopefully, the block is ok.
 
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