My Thrust Bearing is done. Advice please

I was setting up a roller cam and TA stage 1 heads i had purchased from Jim Weise today. I had just finished checking piston to valve clearance and was removing the timing set so i could start on the cam bumper when i noticed the crank moved a bunch when i tugged on the crank gear to remove it. I grabbed the dial indicator and found i had .030" end play, my manual calls for .003-.009. I pulled the pan and #3 bearing cap and lower shell and found the rear side worn down pretty badly and the front side showing copper too. I'm wondering if i can get away with a new bearing or if you think the crank needs to be cut/polished to. I got these pictures before depression set in.

I'm pretty sure i know the answer already but i think i need to hear it from some of you to fight off my urge to toss a new bearing in there, run it for the summer and then deal with it in the fall.

Can any of you New Hampshire/ Mass. guys recommend a machinist that can turn this around quickly enough that i can get to drive it while the weather is still decent?

Thanks for your input.

 

looks like you will need a crank, I have a fresh from the machine shop spare under my bench if you need it. for a good machine shop I always use nasco automotive machine in Saco Maine. not too far from NH
Bryan

 

Im not making a suggestion persay but I would be tempted to put a bearing in it and pull trans have it checked along with the converter and maybe enjoy it till the winter, I mean really wats it gonna do hurt the crank? Too late for that .....and if you find an issue in the verter or trans than that explains the why it happened and will hopefully prevent further damage till you can tear into this winter , it sucks waiting on someone else while your car just sits

 

I was just discussing the issue with my wife and laying the ground work for the inevitable expenditure of funds to repair this and I was saying the real question is what caused it to go bad. I am half inclined to call JW and tell him to start screwing a 470 short block together for me but that is the lazy way out plus until i know what went wrong i'll always be waiting for it to happen again and not enjoying the car. I'm going to have to pull the pistons out and then the crank and measure everything and look everything over and see if i can find a smoking gun. My first thought is the converter as i'm sure most everyone is thinking.

The trans and engine were both rebuilt by Harvey Exner when he owned the car but before I owned it the car didn't get many miles. It has always run really well, great oil pressure no indications that anything was wrong. The trans shifted really quickly on the 1-2 shift unless you were into the throttle hard, it would bark the tires into second and third if you stood on it hard enough but that wasn't very often. How would i tell if the trans ballooned? It looks brand new, there is still a sticker on it from when it was installed.

Any other ideas on where to look,

One thing that struck me is that on the forward bearing thrust face there are oil spreader grooves and on the back there are none or they have been worn away. If that much material wore away where did it go? the pan looked pretty clean when i pulled it , the only funk in there seemed to be non metallic, the oil pickup screen was very clean too, not what i would have expected at all for a failure like this.

 

Tom,

Take it apart, do good cleaning, and then put it back together with a new bearing in it, and use it to located the issue that caused it in the first place.. A "test engine" is what your making now.. You will be watching it closely, so you won't hurt anything by doing this. No worries with the new heads or camshaft.

I would dress the crank thrust surface with some emery paper, clean it up.

Once you get it together, check end play on the stand, and then again in the car, before you start it.. this will be your benchmark, and make sure they are the same. Then drive it, in 5 mile increments, and re-check your end play after each drive. Mix in light and heavy throttle stuff.. You need to know how fast it's taking the bearing out.



First place to start.. beyond insuring adaquate flexplate/converter clearance, and that the nose of the converter is not bottomed out in the crank..

"T" in 0-300 psi in the lower line from the trans to the converter.

Record the pressures under all driving situations in all ranges.

JW

 

Thanks for the advise Jim, one question immediately pops to mind .. how does one accurately measure end play with it in the car? I am assuming you pull the belts on the crank pulley and then remove the converter bolts and knock the crane forward and aft. My question is won't the timing chain inhibit the motion? or are we really looking for a change in measured end play after we are assembled?
I'm no genius on converters, what exactly am i looking for in regards to the converter? When i pulled the engine the bolts came out and the converter slid back off the crank with no issues, what should i be looking for when i put the converter back to make sure its not bottoming out or is this done by measuring?

 

Some good advice on things to check. One more and easiest is the trans cooler. With the engine running put a gauge on the upstream side and downstream side of the cooler, pressure drop should be minimal, if theres blockage there will be too much pressure drop and the pressure will drive the crank forward and eat up the thrust.
My son and I went thru 4 cranks with thrust problems before we discovered this.In 35 years I never wasted a thrust, so we were puzzeled.

Since the cranks were offset ground strokers we welded a coupleup and remachined the journals. The cost to rebalance and grind excedded the repair cost.

No problems in last 2 years after we changed the cooler.
gary

 

Thanks to all for the advice, keep it coming I appreciate it. Thank you Gary for the info on the cooler I would never think of something like that.

I took an hour or so off, washed the wildcat and then tore the rest of the engine down. I found that pretty much every bearing in the engine looks to have some wear on it. Most look like crap. I'll post some photos for you all to consider, first is the main bearing caps, #1 on the bottom , #5 on the top

Next is the #1 rod bearing, this one is down to the copper, sorry for the poor photo

Maybe because the bearing alignment between the cap and the rod is like this

There is a ding in the #3 crank pin where i believe the rod bolt nicked it during initial assembly, i couldn't get a decent picture of it but you can sure feel it. There is a nice corresponding groove in the bearing. there is general wear on all the bearings but they tend to look better at the rear of the engine than in the front so i believe there isn't any oil starvation going on here. What is the general opinion that the thrust bearing going away has caused the wear I'm seeing on the other bearings?

I'm liking Jims idea of replacing the bearings, dressing up the crank and doing some testing to see what happens. At a minimum It'll get me through the summer and then i can tear it down again and see what i have left. Any recommendations on bearings? I'm thinking clevite P series are what I'm after but i'd appreciate any advice from those of you more experienced than I.

 

You won't have any problem measuring it in the car.. done it many times. Crank/bearings always wear on the flexplate sided, because that is where the load is, never on the front. A bearing worn on the front would indicate that the thrust cap was installed crooked.

The timing chain will have enough slack in it to allow the crank to move forward .010 or more.

Simply stick you magnetic based indicator to the trans pan (assuming it's steel) and set up on the flexplate. Pry between the crank flange and the rear cap to move it rearward, and the balancer hub and timing cover to move it forward.. it will move easily.

Don't bet on a whole summer of driving, the last one I dealt with opened the thrust up .006 in 30 miles.. As soon as it opens it up .003 or more, it's time for a new bearing and to change something to locate the cause. You may have the motor in and out of that car multiple times to fix this.. that would be typical for this type of repair.

your workin' now.. :grin:

And Gary is correct, if you find high pressure in the lower cooling line, the first thing to do is swap to the upper, to see if it is the cooler.. and inspect the cooler lines for any kinks.

As far as the trans converter to flexplate fitting, you should be able to pull the converter out at least 1/8th of an inch to have it meet the flexplate, 3/16 is preferred. Inspect if the nose of the converter is bound up/bottoming out in the crank in one of two ways.. IF the converter has to be shimmed back, to achieve the preferred stick out from the trans, then simply remove the shims, and see if the converter will go all the way flush with the flexplate.. if it will , then you are not bottoming the pilot in the crank, obviously..

If you have just the 3/16 or so, then inspect the crank visually when it comes apart, to insure it's not bottoming out.

JW

Yes, use Clevite P bearings in the appropriate undersize.

 

I agree, put it back together with new bearings and set the thrust then check it, over .010" is more than spec, but I've used it, go for it but make sure of your pressures.

One other thing, after reading your description of shifts, its possible the trans line pressure is too much. A lot of people feel if good pressure is fine, more pressure is better so they put in a bigger spring. I've seen pressures over 220psi in the trans fluid which could be an issue, I run 180 in all our race cars. no problems.
gary

 

Clarification..

When I said "the chain will allow .010 movement", I mean on top of the .005-.007 that would be normal. You would not want to allow it to progress any further than about .020 total, as you may start damaging the crank then.

And yes, cranked up line pressure, without the converter feed modification in a 400 is a big problem, but we are getting ahead of ourselves here..

JW

 

I had a thrust go bad in a buddies 470" and it turned out to be the #2 main web. Not trying to scare you but just suggesting taking a good look at the block structure.

 

Make sure you don't have a drive shaft that's too long. If you don't have enough slip travel for the front yoke, you can take out the tranny and/or push the crank forward. Jim P

 

Nope, the driveshaft yoke will bottom out on the trans tail shaft.

I think there was a lengthy and lively thread on thrust bearing failures not too long ago about the fellow with the 65? green wagon.

 

Don't assume it's an original yoke! Could be a longer after market yoke or long caddy from a previous owner. A longer than stock buick yoke will most certainly bottom in the trans during suspension travel. And, a yoke that's way too short can bottom against the output shaft. Both are bad an both can/will damage thrust bearings.

 

Do you have amy dimensions or thing in particular to be looking for on the shaft and yoke? The engine and trans are not original; I'd have to look more closely and and see if the drive shaft has been replaced or not but i'd bet it too has been replaced.

 

I'd be concerned about this if we were talking about a manual trans, but an automatic has a lot of self destructing to do before it will hurt an engine due to a push forward from the output shaft.

You'd see transmission problems first. Big problems.

Devon

 

You'd better believe it. The times I've run into too long a driveshaft and not enough clearance the end result was a broken bellhousing from getting on it off the line or hitting too much of a bounce with the suspension. When you check a transmission for front endplay you always set the trans vertically on the output shaft to take up all output movement. Then you measure the front endplay. The point is if the yoke hits the output shaft hard enough to push the front input shaft forward beyond its range then something just broke, internally or externally.

As far as ballooning converters go I never heard of any run of the mill street going car doing that. It takes some real power to balloon the converter usually with a trans brake. It is not going to do that spinning your tires. I'd say if the converter has slid back on the trans about 3/16" then the converter couldn't have ballooned. I like the idea mentioned about checking transmission pressure in the cooling lines.

Do you know what year the block is? Some of the later years('75-76) had some poor machine work from the factory because the tooling was getting worn out and they were prone to thrust problem. I've seen a bunch of stockers worn from that era. I think the only thing that can fix it is an overbore to get the bores perpendicular with the crankshaft although I'd have to figure the engine is overbored for better pistons if you're going with a roller.

I've put new thrust bearings in a situation like this and run the car. I figured what do I have to loose if the crank wears any worse. It was already going away. I was able to get a few hundred miles out of it but you do need to keep an eye on it as mentioned.

 

When you're assembling the engine, make sure to "drive in" the thrust bearing. If the cap is not positioned right, only 1/2 of the thrust will contact and it will wear rapidly if there is any pressure on it.

You want to check thrust clearance with the main cap off first.
Next, install the thrust main cap and seat it with the bolts. Then, loosen the bolts slightly and tap the rear crank flange forward with a hammer and soft metal block so that the thrust flange contacts the bearing 360
Finally, torque the cap and recheck the thrust clearance. It should be within .001 of the reading you got with the cap removed.

Sometimes, you may need to "dress" the bearing slightly on a surface plate and abrasive paper. Dying up the thrust side of the bearing and spinning it with pressure will tell where the high spots are.

I noticed that your cap is ground parallel on the side to the parting surface. That's a good sign that the housing bores were properly machined. That step reduces the possibility of the cap being crooked unless it was cut at a previous time in it's life and not indexed.

As mentioned, polishing the thrust surface with an Emory cloth, in the direction of rotation will help. Using a stiff wooden stick as a backer for the paper helps.