Thrust Bearing Woes

[6667fan]

After repairing a broken Erson rocker arm in August I performed an oil change and was shocked to see a lot of gold colored flecks in the oil. They did not appear burnt and were very fine, no chunks. The chassis my 482 is in is a 67 Fairlane so there is no drop the pan and check some bearings. I could put a dial indicator on the crank pulley and check the crank movement which was found to be .014 without prying on anything. Well, that sucks. I had been babying the engine and cycling a new clutch since the engine went in during May '19. The whole goal was to get the car to the track last fall so this news was quite a blow. I shared some pics with Brent to get some input on what might have happened and should I take the thing to the track anyways. He advised against it but I decided to make a few passes and recheck the crank walk, ( it grew .005). It was a gamble but I had to know how that build might perform. Car went 11.8 @122 mph. After spinning through first in the hole it grabbed enough in second to get some daylight under the wheels.
I had to wait until this week to have the builder take it apart, (in his shop there are literally blocks stacked hip high everywhere). The amount of crank movement shown after prying it was .016. The crank face exhibited .005 wear. The builders plan is to prick punch the surfaces to tighten things up as opposed to building the crank surface up. He says this method is commonly used but I would like to hear opinions on this approach.
There is of course the question of what caused the wear and where the flecks came from. The thrust bearing itself is not shedding copper and there is a, ( Brent, please put hand over eyes), plastic distributor gear. Cam bearings are decent and the heads have not been checked yet. Rod and main bearings not the culprit.
One thing that I will be doing differently is not pushing the clutch in to start engine. I had got into the habit of that to take a little load off the starter but I can't risk putting any unnecessary load on the thrust bearing when the oil is not moving. I don't know what is responsible for the wear. I'm not pointing the finger at the builder.I had trouble getting the toploader installed and thought for awhile maybe I loaded the crank. I never ride the clutch. The linkage is stock but there is a Lakewood bell. I mention that because I can't be certain the Lakewood fulcrum point is not mechanically over leveraging the clutch. The T/O bearing was set up with plenty of free play and is not burnt.
Thoughts/suggestions?
Thanks,
JB

[BattlestarGalactic]

Um, I'm no expert, but "pricking" the thrust surface is not what I call a real fix.  Something someone would do when stuck in nowhere land with no other options.  For a real performance build I would not suggest that.  My .02

I also do not push the clutch to start any of my vehicles(big or small).  I too learned 30 yrs ago with 3000# clutches that it would not be good on the thrust so I never do it to this day even with my very soft clutch in the wagon.

My very first rebuild, a 302 in my '70 F100 back in 1985 washed out the thrust in like 100 miles.  It had like 1/4" slop!!  It was bad.  Never did find out what caused it. I built a new motor and never had that issue ever again.  I'm going off memory, but isn't thrust like .008-.012 range when new?  What was yours when new? I wonder if it was too tight to begin with causing crank wear.  Once it got rough, it just kept eating itself.

[drdano]

I'd have the crank welded and reground, it's not that expensive.  I'd also have the block carefully looked at on #3, as it may now need an align hone after the crank was gnawing on the thrust bearing heating it up.  I had the same thing happen, caused by too long of flywheel bolts digging into the rear main saddle and pulling the crank rearwards.  I've also seen the trans input shaft too long, burying it in the crank pilot hole and pushing on the crank.  This happened for a reason, somewhere, up to you to find it.    

[jayb]

Make sure that when the trans is bolted up, the input shaft is not bottoming into the end of the crank, or pushing against the throwout bearing (bushing).  You need some clearance there.  Aftermarket cranks aren't cut as deep in the throwout bearing area as factory cranks, and this has caused me some trouble with converters bottoming out against the crank.  Fortunately with a converter you can wiggle it front to back to confirm you have clearance; not possible with a manual trans. 

[chris401]

The spec mentioned is right. I went through that on a 390 that had .009". The book I had listed .010" max. Sounded like a hammer lightly tapping the flywheel.

Thanks for the reminder Larry, I remember dad telling me that 28 years ago when I installed that linkage breaking Center Force clutch.

[BattlestarGalactic]

Funny, I still run a DF CF clutch in my '69 F100.   When I push the clutch, it actually pulls down on the dash hard enough it moves the steering wheel. LOL!  Been running that same clutch for over 25 yrs now.

I've wanted to lengthen the Z bar to make it have better leverage, but there isn't enough room to change it enough to make any difference.  I even fabbed my own years ago and put grease fittings in it to help keep it from tearing stuff up.

[cjshaker]

x2 on the "prick punching". No way is that an acceptable practice, and I'm surprised any machinist would even suggest that. Unless it's a perfectly smooth surface, it'll only dig into the thrust bearing and chew it up.

I never push in the clutch when starting, for the same reasons about lack of oil. But 'newer' stick shifts require you to do that. My '09 Mustang and my '05 Ranger have that "safety" built in, and I release the clutch as fast as possible so oil can get to the thrust.

Same thoughts on checking the input shaft to make sure it wasn't bottoming out. Sounds like you have good practices as far as not holding the clutch in and taxing the thrust bearing, so if something wasn't pushing the crank forward, I'm not sure what else could be the cause, other than a defective bearing or improperly machined thrust surface. Does the input shaft of the tranny pull forward? Because of the bevel in the gears, the shafts in the tranny naturally want to spread apart (fore and aft), so if the input shaft has room, it can walk forward, pushing it deeper into the crank. Just a thought.

[blykins]

With new crankshafts, I routinely see about .004-.006" of thrust clearance.  That fact that it grew while you were racing, to me, shows a bearing issue.  I'd like to see pictures of both thrust bearing halves, on each side.

What he's proposing is essentially the same as "knurling" pistons.  I wouldn't do it.  It needs to be welded up and reground.   If he took any notes when he assembled, he should know what he started out with.  That would be a good indicator of what has changed.  I write down the thrust clearance with the top bearing half in only, and then with both, so I can adjust accordingly.

Most thrust bearing issues that I've seen or heard of have been clutch or transmission related. 

[cammerfe]

For what it's worth, if you use a small-block input shaft transmission on an FE the longer small-block shaft may very well push the crank forward. Sometimes it does not-good things to the thrust surfaces, and it's been known to do damage on the two-six crank throw as well. I lost an engine on a dyno because a small-block drive 'spud' was used in setting up the dyno. It is longer and pushes the crank forward at least some of the time, depending on tolerance stack-ups..

KS

[StarlinerRon]

I put a Hayes 3200# in one of my cars (AMX) and it wore out a TB in a summer of crusin.

Ron.

[6667fan]

The pocket at the back of the Scat forged crank is very deep. The T/L input can’t get there in this application. BUT I have to consider if the shoulder of the input was putting pressure on the pilot bushing. No measurements of crank end play were taken after the drivetrain was installed and I did have a battle getting the T/L “home”. I’m speculating that I loaded the crankshaft when I installed the trans and three months later became aware of the resulting excessive endplay from trans pressure/thrust bearing wear, ( after finding what looked like bearing material in oil).
Going to be speaking with builder about options this week.

Thanks,
JB

[My427stang]

Any marks on the pilot bushing?  If it was rubbing it would have clearanced itself, not saying it wouldn't take out the thrust, but you'd see it...same with the bearing retainer and the clutch disk

[Leny Mason]

I would rethink about the builder If he wanted to do that to Your block, He is very wrong about punching the bearing stops, and You still haven't found were the brass came from My 2 cents Leny Mason.

[drdano]

I did have a battle getting the T/L “home”.

That would make me very suspicious of everything behind the motor.  Time to mock it up without the clutch and fork so you can peek through the window and see what is really going on and verify nothing is hitting.

[Heo]

Do you have the block plate ?