Goofy Thrust Bearing Gaps

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T56MaxTorq

T56MaxTorq

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Building a 318 mag for turbo boost. Had the thrust bearing go out on the previous crank in this block. I added main cap studs. Took measurements for them and they checked out ok - no need for a line bore/hone. Installed the crank and checked the thrust bearing gap. Problem is that I have a total of .007” gap which is ok. But that is only on one side. The other side I only get .005” Even if I rotate crank 180*, I get the same measurents on the same side of the bearing. So the crank is true but the bearing is sitting crooked. Tried multiple times of removing and resetting, torquing the cap and bearing but no dice, won’t become true. Any ideas?
 
Did you give the crank a tap with a hammer on the snout (to send it rearward) and then on the flywheel end of the crank (to send it forward, this being the desired end result especially with a standard transmission), (with the torque spec of the thrust cap tightened just enough to hold it in place) this should help "set" the thrust to the location it wants to be at. Then tighten up and re-measure.
 
Yes, I had the #3 cap finger tight, hit with dead blow aft, pried foreward while torquing to 15 ft lbs. Then torque to final in 3 equal steps.
 
stroker416 said:
Just as a reference have you miked the thrust faces on this bearing set and compared them to another?
Click to expand...

I have not but I can measure the thrust face I have. Don’t have a reference but maybe Mahle can shed some light and give me a measurement spec.
 
T56MaxTorq said:
Yes, I had the #3 cap finger tight, hit with dead blow aft, pried foreward while torquing to 15 ft lbs. Then torque to final in 3 equal steps.
Click to expand...
That is not the same technique described by Max1196. You must hit the crank from the rear w/that deadblow, and not a baby tap either, after You rapped it from the snout.
Simply prying on it ain't going to do it, smack the damn thing! Also, I'm not sure which "side" You are referring to, Upper shell vs Lower shell? You can't have a "total" of
.007", if You've "only got .005" on one side", it don't work that way. Interpreting what You seem to be saying, You have a maximum gap of .007", but the thrust is really
only .005" total due to the "tight side". Is this correct?
 
I'd be curious to know how the prior thrust bearing failed.

If you pry the crank in the opposite direction, do the gaps sizes switch sides? If the problem is the bearing cocked at an angle, they should.
 
I’ll try and answer everyone’s questions in a single post.

Overall endplay is the smallest value of .005, sorry for the confusion.

No I didn’t initially dead blow fwd but I did beat it fwd the third time and no, it didn’t change the measurements. I used a medium sized crowbar to pry fwd while torquing. However, I could probably whack it harder and use a bigger lever.

Killer6, your interpretation is right. The total is .005 due to the tight side but I have larger gap on one side. With the crank upwards, I’m measuring with a feeler gauge on the left and right side of the main cap while lightly prying the crank forward. I get measurements of .007 on the right side, only on the cap. As soon as I touch the lower bearing shell in the block, it’s .005. I get 005 on the left, upper and lower bearing. Pry aft and I get a larger gap on the left than the right. I think I may just have answered my own question and the cap is just not centered properly. I’ll have to really hammer fwd and pry harder while torquing. If I still cannot get it perfect, what do we do from there???

Original thrust bearing failure cause is unknown. I think it was a torque converter ballooning or the tq simply had ultra high pressures and pushed it fwd. I didn’t check line pressure and that was my fault. The thrust was worn out on the aft part, cap side mostly. Others thought that the transmission install went wrong, but I didn’t damage the transmission pump and the engine ran 10 hrs or so before the discovery.
 
Interesting... actually the main cap may be fine but the shell cocked in the cap. Check the cap surfaces and where the shell contacts the cap and make sure there are not burrs in there.

I am really not sure that being equal on both sides is all that critical, as long as top and bottom halves are generally aligned. I know I have never worried over it..... and have seen one half of a thrust bearing worn more than other halves on one side only with no adverse effects, so it must happen. I don't even recall ever measuring on the sides.
 
So you installed main studs and "measured" it and it came out ok so no align hone. How did you measure it? Just the crank bore diameter? If so the studs can pull the bores out of alignment.
 
Stroker416 and furrystump are both on here;
1) get a mic and check the overall width, thrust-face to thrust-face on both shells in 4-5 places, and check the thickness of all 4 thrust faces the same. If they are spot on....
2) use the OE bolts and repeat setting/seating procedure for the thrust bearings & re-check, same results or OK? If so, You may need to clearance the bolt holes in the cap(s)
to prevent the stud shoulders from pushing the cap(s).
 
nm9stheham said:
Interesting... actually the main cap may be fine but the shell cocked in the cap. Check the cap surfaces and where the shell contacts the cap and make sure there are not burrs in there.

I am really not sure that being equal on both sides is all that critical, as long as top and bottom halves are generally aligned. I know I have never worried over it..... and have seen one half of a thrust bearing worn more than other halves on one side only with no adverse effects, so it must happen. I don't even recall ever measuring on the sides.
Click to expand...

I’ll have to take the crank out and see if there is anything obvious. I only measured with a feeler gauge on the sides because of the previous failure. Maybe .002 difference is just fine and the bearing will shed its coating and true-up. I’d hate to pull it all apart again. I did slightly taper the edges of the eccentric part of the bearing on both upper and lower shell to allow more oil flowing to the thrust surface.

furrystump said:
So you installed main studs and "measured" it and it came out ok so no align hone. How did you measure it? Just the crank bore diameter? If so the studs can pull the bores out of alignment.
Click to expand...

I measure the crank and installed bearings in the caps with a micrometer when torqued to spec. No change vs stock bolts. Also checked with plastigauge and the measurements were slightly tighter but good.

Killer6 said:
Stroker416 and furrystump are both on here;
1) get a mic and check the overall width, thrust-face to thrust-face on both shells in 4-5 places, and check the thickness of all 4 thrust faces the same. If they are spot on....
2) use the OE bolts and repeat setting/seating procedure for the thrust bearings & re-check, same results or OK? If so, You may need to clearance the bolt holes in the cap(s)
to prevent the stud shoulders from pushing the cap(s).
Click to expand...

I’ll try this thank you.
 
Have the block align honed with the studs. It's mandatory as far as I'm concerned. I've also had to have the holes in the caps enlarged slightly in rare instances to get things to be right.
 
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