Excessive Crankshaft End Play

[65longroof]

400 Pontiac engine, fresh built, #16 heads, approx 10-10.5:1 comp, 068 hyd cam (tame by today's standards), quadrajet, hei ignition, Brad Penn "green" oil. Mated to a TH350.

First time around ~ 1000 miles, rear seal started leaking, took engine out and found neoprene seal fell apart, new balancer cracked, t-stat wasn't opening fully and thrust bearing was worn. New bearings installed, new balancer, rope seal and t-stat.

Second time around (less than 1000 miles), tapping starts when engine has a load on it. After a wild goose chase finally diagnose it to the flexplate hitting starter gear (mini-starter). Starter can be shimmed in two planes so plan is to add shim moving starter gear further away from flexplate, towards the front of the car. Wanted to turn crank to see if flexplate was "wobbling". In doing so, I noticed that the crankshaft moved to the back. I measured the endplay (crudely in the car) at 0.067"! Way more than the recommended .003-.009"

Called my machine shop and he thinks some possibilities are:
ballooning torque convertor
restricted trans cooler line causing pressure in convertor to push against crank

Going to take the engine in to see if there is anything internal causing the excessive wear.

Any other ideas to look for?? I'm going to put a Pontiac 350 back in for the meantime. This will allow me to drive it some and if necessary diagnose any trans issues.

[hauen]

I pulled down a small block Chevy one time that had massive wear and excessive thrust, turns out the genius who thought he was Smokey Yunick lost the dowels on the cap so it was walking around. It's the only time I've ever seen something like that, but he was a firm believer in having a wrench in one hand and a beer in the other.

[OldMachinist]

Those are two common problems that take the thrust out. I've probably welded a hundred 350 Chevy thrusts because of it.

[65longroof]

Thanks for the replies guys. Got the motor out tonight and will drop it off at the machine shop Thursday. Hoping to find something either internally or with the trans, if not, I'm going to be very reluctant to put the 400 back in...

[65longroof]

Took converter to a local performance trans shop that builds converters (Competition Transmission). Converter had 0.015" of runout in the drive hub and was not fully engaging the pump. Hub also showed signs of wear from the front seal indicating that it may have been running a little cock-eyed or not straight. He recommended building a new converter for it, should have it done within a week. Machine shop has not torn engine down yet. Once I get the converter, I'm going to put the original 350 c.i. back in for the rest of the summer so I can at least drive it.

[groucho]

Did the 1st time around damage the thrust surface on the crank, causing the 2nd set of bearings to wipe out prematurely?

[65longroof]

Did the 1st time around damage the thrust surface on the crank, causing the 2nd set of bearings to wipe out prematurely?

Supposedly the crank was fine, just the bearing had some wear in it.

Update:
Got the new converter and put it in along with the orig 350. The gap before moving the converter forward to the flexplate was about 1/4". The gap on the 400 and old converter was about 3/4", most likely causing the problem by barely engaging the pump. Haven't heard from the shop yet about the extent of the damage inside the 400.

[groucho]

Supposedly the crank was fine, just the bearing had some wear in it.

Update:
Got the new converter and put it in along with the orig 350. The gap before moving the converter forward to the flexplate was about 1/4". The gap on the 400 and old converter was about 3/4", most likely causing the problem by barely engaging the pump. Haven't heard from the shop yet about the extent of the damage inside the 400.

what does the converter barely engaging the pump in the trans have to do with what happened to the thrust in the motor?

[65longroof]

what does the converter barely engaging the pump in the trans have to do with what happened to the thrust in the motor?

The end of the drive hub is slightly tapered/chamfered to aid alignment when putting it in. If the converter isn't seated fully into the hub, it could allow the converter to run at an angle putting unconventional forces on the crank. There was evidence of this on the old converter as you could see the seal was putting a wear pattern on it at an angle. This is the only thing I've been able to find that could cause the thrust bearing to wear, so far. The hub also had about 0.015" of runout, which didn't help matters.

If the shop finds anything else inside the motor, I'll be sure to post an update.

[groucho]

The end of the drive hub is slightly tapered/chamfered to aid alignment when putting it in. If the converter isn't seated fully into the hub, it could allow the converter to run at an angle putting unconventional forces on the crank. There was evidence of this on the old converter as you could see the seal was putting a wear pattern on it at an angle. This is the only thing I've been able to find that could cause the thrust bearing to wear, so far. The hub also had about 0.015" of runout, which didn't help matters.

If the shop finds anything else inside the motor, I'll be sure to post an update.

Gotcha. Let me ask....why'd you continue to assemble the package in the 1st place with 3/4" between converter and flex plate? Risky shit right there. I'm surprised it didn't wipe the pump instantly. I've seen pumps go away immediately when guys use a Powerglide flex plate on a TH350 or 400 with less than 3/4"...but more than is supposed to be there

[yellomalibu]

If the converter is more than 1/8" away from the flex plate, use spacers or washers between the two when bolting them together, so that the converter pulls out of the transmission about an 1/8" - which is required for thrust bearing longevity. If the gap is less than 1/8" then the converter probably isn't seated in the transmission properly or something else is wrong.

That was what the instructions on one of my converters said to do. Either the TCI or the B&M.

[65longroof]

Gotcha. Let me ask....why'd you continue to assemble the package in the 1st place with 3/4" between converter and flex plate? Risky shit right there. I'm surprised it didn't wipe the pump instantly. I've seen pumps go away immediately when guys use a Powerglide flex plate on a TH350 or 400 with less than 3/4"...but more than is supposed to be there

I guess I just didn't know any better at the time... Learning something new everyday, but learning the hard way can be a lot of work sometimes!

[65longroof]

If the converter is more than 1/8" away from the flex plate, use spacers or washers between the two when bolting them together, so that the converter pulls out of the transmission about an 1/8" - which is required for thrust bearing longevity. If the gap is less than 1/8" then the converter probably isn't seated in the transmission properly or something else is wrong.

That was what the instructions on one of my converters said to do. Either the TCI or the B&M.

The gap was actually less than 1/4", I didn't measure it. The guy that built the converter said if it got to be more than 1/4" to put spacers in.

[groucho]

I guess I just didn't know any better at the time... Learning something new everyday, but learning the hard way can be a lot of work sometimes!

Yes, but at least we learn, right? I've seen guys make the same damn mistake, over and over

[yellomalibu]

On thrust bearing longevity:

With a manual transmission, does sitting at traffic lights with the clutch pushed in for minutes at a time wear the thrust bearing? Enough to worry about it?