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6 bolt thrust bearing failure

brian9397gsx

Proven Member
1,559
93
Apr 28, 2008
sioux city, Iowa
Hello all, my problem is my thrust bearing on my 6 bolt has failed. the engine has maybe 6 passes and a few hundred miles.
I noticed the problem when I dropped my trans, Im switching to an automatic set up, I noticed my flywheel would move in and out a good distance about 1/8 of an inch. Ill drop my pan tonight and inspect the mains but I know the thrust is trashed.

Its a stock rebuild that I did 5 years ago but the car doesnt get drove hardly ever but Im hoping that will change.
When I assembled the engine I followed the fsm and used a feeler gauge on the thrust and it was good.
Im looking for first hand experience with what I can do to avoid this in the future. I think ill drop the pan and if everything checks visually I will throw some new mains in.

whats the right way of setting thrust? I always ran rotella 15 40 in the engine. Open to any suggestions on what to look for my gues is the two halves were not completly in line and it caused this issue.
 

hotrodssnova

Proven Member
696
46
Feb 14, 2009
Houston, Texas
Having to push the clutch in to start can have this result. Also the heavy pedal clutches will cause this. Since you're going automatic, that takes the clutch out of the equation.
 

brian9397gsx

Proven Member
1,559
93
Apr 28, 2008
sioux city, Iowa
Thanks for the reply clutch was a xtd stg 4 cheap ebay one. And clutch switch has been disabled for about 10 years. I really think it was with the setup of the thrust bearing or machining of the crank.

I'm really looking for what some of the engine builders on here or really anyone who has successfully set up the thrust bearing. Just so I don't have this issue on my future build.
 
Last edited:

Mello

15+ Year Contributor
1,473
622
Jul 4, 2003
Albuquerque, New_Mexico
Your crank & block are probably trashed if your crank end play is 1/8 inch. Mine was trashed & my end play was only 1/16 inch. Crank ate into all the mains & everything was garbage. Salvaged the head though.
 

brian9397gsx

Proven Member
1,559
93
Apr 28, 2008
sioux city, Iowa
Right that's probable, I'll find out tonight when I pull the pan. Still doesn't help with my question. I'm just guessing the measurement I didn't have my dial indicator.

If it's trashed it's trashed I don't really care what I do care about is repeating it if there's a problem with my assembly. I'd like to not repeat it.
 

hotrodssnova

Proven Member
696
46
Feb 14, 2009
Houston, Texas
When I assembled my 6 bolt bottom end, I snugged the mains down and took a rubber mallet, and tapped the crank forward, then backwards. Torqued the mains, then checked end play.
 

brian9397gsx

Proven Member
1,559
93
Apr 28, 2008
sioux city, Iowa
Yeah that's what I did, and checked with dial indicator and feeler gauges and it was good then. The bearings are acl tri metals.
 

curt-s

10+ Year Contributor
1,596
355
Dec 21, 2008
Winnipeg, MB_Canada
i stopped using acl trimetals a few years ago when i found rod and main bearings in two separate packages both having deep gouges from something sharp.
youll identify the source when you pull the main thrust.. did your crank mic out for diameter and fillet?
 

brian9397gsx

Proven Member
1,559
93
Apr 28, 2008
sioux city, Iowa
I did not when I assembled it. I put my trust in the machinist (very reputable guy) I did mic all the clearances going together and everything was good. But I ll know more tonight or tomorrow morning depending on the weather.

Good to know about the acl s I'll use a different bearing next time. I'm also guessing starting it once a year might not of been good on things either.
 

Mello

15+ Year Contributor
1,473
622
Jul 4, 2003
Albuquerque, New_Mexico
The truthfully answer is crankwalk can happen to any engine. No one can tell which are going to walk or not. There are lots of theories & superstitious remedies but there is no real data or guarantees to support anything.
 

brian9397gsx

Proven Member
1,559
93
Apr 28, 2008
sioux city, Iowa
Right thanks for that but what I'm asking is specifically if there's something wrong with my assembly process that I should correct. Like should I load the crank during torque I've seen that mentioned. Or anything else I should pay particular attention to during the assembly process to decrease the odds in the future. I don't feel it was chance.I'll tare into it tonight
 

brian9397gsx

Proven Member
1,559
93
Apr 28, 2008
sioux city, Iowa
Well I tore into it tonight beforehand I measured thrust with my dial indicator and I had 45 thousands of an inch. When I drained the oil it smelled like gas so I'm guessing that is my culprit combined with the heavy clutch the oil didn't have a chance. I'll be sure next time I store it to start it more regularly than once a year. The thrust bearing was pretty rough but I think I caught it in time rods look decent. I'll try sliding in new bearings and probably move my engine build up sooner rather than later. Thanks for the replies .
 

bjones18

Proven Member
299
32
Jun 3, 2004
canton, Michigan
Search crank-walk, and find a tech article I wrote for adding a second thrust for 7-bolts. It should work for 6-bolts also. It's quick and cheap. more thrust surface is good.

Reading through procedures for setting thrust bearings is confusing... push this way...hammer that way...

The best method is to think about the stack-up: Block/cap/bearing.

You want:
a. the bearing thrust-surface top/bottom to contact the crank simultaneously.
b. the block to provide axial support to the top thrust
c. the cap to provide axial support to the bottom thrust.

The knocking procedure uses the crank-thrust surface to line-up these bearing & structure surfaces.

I hope this is helpful.
 

brian9397gsx

Proven Member
1,559
93
Apr 28, 2008
sioux city, Iowa
My apologies for the all caps in the title, sorry it offended you. But like I said before I believe my thrust failure was most likely caused by oil contamination. I did remove the bearing the rear thrust flange is close to gone. Luckily there was no contact with the crankshaft and block, but I'll be writing it off. I've got two other blocks and I'm weighing my options on each one.

Thanks to everyone who chimed in. Everything that was linked and opinions I will take into consideration on the next engine to hopefully prevent this from happening again. The more information I've seen and heard from you guys further reinforced my belief that the assembly was not at fault.
Thanks again
 
Last edited:

donniekak

DSM Wiseman
5,623
973
Mar 23, 2008
Surprise, Arizona
Is your clutch adjusted properly? If the master cylinder rod is adjusted out past the bleeder hole, the slave will keep constant pressure on the pressure plate. This will keep the crank pressing against the thrust constantly.

Also, I've seen a lot of cranks with thrust issues with a cupped surface. The crank will seem ok when first installed and measured, but after just a few cycles it will eat into the thrust bearing.
 

brian9397gsx

Proven Member
1,559
93
Apr 28, 2008
sioux city, Iowa
Cupped surface on the crank thrust section? That I'm not sure. The clutch was adjusted properly initially but as the wear got worse and worse it wouldn't disengage very well as expected. I never messed with it after that I just parked it, that was about 2 or 3 years ago and the most driving it's seen in that time was pulling it on and off a trailer 3 times. I'm writing that block and crank off , well the crank at least it's been cut .025 already and I have 2 other blocks to mess with.
 

untouchablecc

10+ Year Contributor
852
12
Mar 21, 2008
Mt. pleasant, Pennsylvania
The service manuals usually all state what was mentioned earlier. Snug the mains, tap the ends of the crank to "set " it. Then tighten the mains and measure end play.

In my experience and the was I have done the 10 or so 6 bolt engines and 1 2jz engine I have built was to simulate a clutch load on the crank when tightening the thrust bearing cap.

I follow what ever torque specs stock or ARP scenario dependant. Then torque the front main cap, rear, then the thrust bearing last. Before I go to torque the last cap I use a pry bar between the crank and block, apply force toward toward the front of the engine to kind of act as a pre load for the clutch. I have never had a crank walk or destroy a thrust or main bearing in all the engines I have assembled.

My 2jz has a completely different main cap torque sequence from dsms and like 5 or 6 main caps. I did the exact same thing to it. Never had any crank issues.

I hope this helps some.
 

brian9397gsx

Proven Member
1,559
93
Apr 28, 2008
sioux city, Iowa
Yes it does , good information guys I won't use this crank again. The thrust area is indeed questionable. I think donniekak was onto it the rear thrust area of the crank is uneven, hard to mic with what I have on hand. This is the only motor I've had thrust a thrust issue with.
 

bling5tatus

15+ Year Contributor
1,584
110
Sep 23, 2005
DFW/Austin, Texas
I crank walked a 6 bolt by trying to adjust out a warped pressure plate. It was a 2900lb ACT so it wasn't being nice to that thrust bearing and since it's such a heavy clutch it just squished the clearance so much that it ate up the thrust bearing. You can definitely crank walk a 6 bolt or any other motor for that matter.

You're likely looking at getting a new block/crank.
 

curt-s

10+ Year Contributor
1,596
355
Dec 21, 2008
Winnipeg, MB_Canada
I'm not at all surprised a 2900lb PP would kill a thrust bearing, especially if all variables aren't perfect 100% of the time -- bearing alignment, crank balance, axial alignment, oil pressure and flow across the thrust surface, the list goes on. For those that need that sort of clutch, they have to expect to trash motors continually.
 
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