Resolved 6 bolt Thrust Bearing Install Problem

[TalonFan]

I am in the process of putting my 6 bolt back together. I'm installing the refreshed crank back into the original block. The main bearing journals were line honed when the block was prepped along with the cranks. When I had it all installed and torqued down, the crank would bind slightly when I rotated it by hand. Once I took it all apart again and did some investigation, it seemed that the crank was hanging up on the thrust bearing. I have just .002 clearance, and then that clearance goes away in one spot on the rear side when the crank is turned. The crank will still turn; it just gets a bit tight.

I have tried cleaning the bearings again and using fresh assembly lube, retorqued the cap. It still happens. Should I be looking into a bent crankshaft? It seems like I should have more than .0015 - .002 clearance to start with.

Any thoughts or direction you can give me? Thank you all in advance.

 

[motomattx]

Do you have another crankshaft that you can bolt in to try out? it sounds like a crankshaft that is not true to me if the machine shop is trust worthy.

 

[TalonFan]

Unfortunatly no.
I can take it to the shop and get them to check it out. They polished the journals for me, but I didn't ask them to check out anything else because I didn't have issues with it when I took the engine apart. I have used them for all my other work, and they have never let me down so far.

I hoped there was some obscure alignment procedure I had never heard of rather than spend extra money on more machine work. Cheaper than having to rebuild the engine again when it spins the bearing.

 

[curt-s]

I wonder if they bent the crank when doing the work. You need to get it checked on rotation. Sometimes things happen and nobody says anything
The place I had my head done didn't realize their pilot was bent when they cut valve seats, so all the seats were uneven. Of course, a simple test even without the springs installed would have clued them into that one..
Also double check that you don't have any debris that was caught under any of the bearings. Even the tiniest bit can cause it to not seat properly.

 

[TalonFan]

Thanks for the input. I'll run the crank to the shop and have them look at it.

 

[DSMPT]

I am in the process of putting my 6 bolt back together. I'm installing the refreshed crank back into the original block. The main bearing journals were line honed when the block was prepped along with the cranks. When I had it all installed and torqued down, the crank would bind slightly when I rotated it by hand. Once I took it all apart again and did some investigation, it seemed that the crank was hanging up on the thrust bearing. I have just .002 clearance, and then that clearance goes away in one spot on the rear side when the crank is turned. The crank will still turn; it just gets a bit tight.

I have tried cleaning the bearings again and using fresh assembly lube, retorqued the cap. It still happens. Should I be looking into a bent crankshaft? It seems like I should have more than .0015 - .002 clearance to start with.

Any thoughts or direction you can give me? Thank you all in advance.

Hard to tell without measuring. This could be a bent crank but could be the block or the main cap side issue. Or also could be a wrong bearing set you have.
Is the crank new or taken from a undamaged engine or damaged engine?
You had the block line honed. Can you remove the main bearing #3 from the main cap and journal by hand? If it's stuck and difficult to remove by hand, may be cut too much and the thrust groove is not tall enough anymore. If that's the case, when you torqued the main bolt once, the thrust would be pushed towards outside by the edge of thrust groove on main cap, and the thrust may touch the crank.

 

[TalonFan]

When I pulled it apart, the engine ran fine, and there was no damage. It was just a tired engine I wanted to refresh before mucking around with upgrades. All the bearings fit nicely and can be installed and removed by hand. All of the oil clearances are good too. It's just the end play that's inconsistent through a full rotation.
That said, I see your point about the bearing being pushed out. I will inspect the cap and torque it down without the crank installed and take a look.

 

[donniekak]

Make sure there’s nothing on the backs of the center bearings or the machined thrust surface of the block. Measure the center bore with a bore gauge to see if the bore is in spec for bearing crush. You also need the wack the crank in both directions with a deadblow before final torque on the center main.

As for the crank put a straightedge on the thrust surface to check for wear. You can also set it up in the block with just the top end mains installed and a dial gauge to see if it’s bent.

 

[TalonFan]

I thought I would complete this.
I measured everything again, and all my clearances were correct specifically .004" end play. I took it to my engine builder, and he had a look. I learned the following...

Never rotate the crank counter to normal rotation. While I am embarrassed to acknowledge this, maybe someone else will read this and not have to swallow their pride publicly. With the Lucas assembly lube I'm using, the counter rotation can (not always) push the crankshaft against the thrust bearing just enough to create a bit of friction at different spots. This is why I wasn't getting the resistance consistently through 360 deg of rotation. Rotating the crank in the right direction doesn't do this. A lighter assembly lube may also not do this as badly.

I wouldn't have believed him if he hadn't taken the time to show me.

Now I know. Thanks for your input. It's much appreciated.,

 

[1990TSIAWDTALON]

Thank you for the follow up to put a solution to this thread for the future.

 

[curt-s]

...

Marty, do you agree with this? This is the first I've ever heard that an engine can (even by the smallest of chances) bind against a bearing when rotated opposite to normal and this should be ratified before it becomes misinformation, if it is.

 

[1990TSIAWDTALON]

Curt, TBH, I have NEVER ever heard of this. I do make it a point to always rotate my motors in the correct direction but, either direction should yield the same results.
I have built engines since 1978 and never had this issue. Next 4g build I do, I will INTENTIONALLY rotate it backwards to check this claim. The DIRECTION of rotation should have NO EFFECT on the thrust surface. The thrust surface of the bearing could be wonky or the thrust surface on the crank (or a bend in the crank), but it should not matter what direction the assembly is rotated in in any case.
I too, would like to see proof that this is the issue, not a bad crank or bearing.
Also, Lucas itself, is thick enough. IDK about their assembly lube but I have used this since DAY ONE and reccomend it to any engine builder.

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