Main Bearing Help!

Posted By: chris3

Main Bearing Help! - 09/19/10 03:33 PM

I have a 340 block. The crankshaft has been turned .010 and polished. Bearings installed in the block and the mains torqued. Inside bearings measured against the crank dimensions and across the block all mains have 0.003 clearance. Install the crankshaft, torque the main studs and the crankshaft will not turn. Removed the caps install caps one at a time torque the main studs and the crankshaft will not turn with only any one cap in place. What am I missing here? Have not measured inside the caps before installing the bearing but if it has a consistant 0.003 clearance on each bearing I would think there is not a problem with the bearing thicknesses. Align hone the block? All suggestions are welcome we are just missing something here.

Pinks All Out a Bristol is coming soon.

Posted By: snook

Re: Main Bearing Help! - 09/19/10 04:07 PM

check that the MB edges aren't into the journal fillets. May have to shave the MB's?

Posted By: HotRodDave

Re: Main Bearing Help! - 09/19/10 04:57 PM

If your crakn has chamfers and the bearings are too wide they could be hitting the edge of the curve and locking it up.

Posted By: 416challenger

Re: Main Bearing Help! - 09/19/10 05:05 PM

Also check the number 3 thrust bearing.

Posted By: Cab_Burge

Re: Main Bearing Help! - 09/19/10 08:09 PM

Do you know how much main journal crankshaft run out you have? I had similar problems in the past on stock 318 steel cranks, they where bent on the number 2 journal(both, three years apart

) .0018 which with .0022 clearnances would not allow the crank to turn 360 degrees

I ended up doing the

no no and used scotchbrite to enlarge the bearing clearances

I should have taken both in for straighting

but I was in a hurry and both of those motors where going into my own cars that me and my wife drove as dailey drivers, both ended up working well for a long time with no problems that I know of, one car got total in a wreck and the other one was sold and went down the road for over 50000 miles before the new owner put a 360 in it

Posted By: chris3

Re: Main Bearing Help! - 09/19/10 08:31 PM

More news. The bearing are set back such that the edges are not hitting the champher on the crankshaft. Set the crank shaft in place turns free. Took the crank back out removed the center thrust bearing. Set the crank back in place. Checked end play with the shaft in place on the bearings and would move laterally and turn smooth. Put all of the caps on. Torqued the studs to 15 foot pound and the crank would not turn. Took each cap off, one at a time, and crack would not turn until the last cap was removed.

This crank has been checked for straight, the journals turn .010, polished and balanced.

Only possible thought at this point is that the caps are not aligning with the crankshaft. Thanks MOPART for all of your help. Anyone else got any ideas.

Posted By: chris3

Re: Main Bearing Help! - 09/20/10 12:19 AM

Posted By: 64physhy

Re: Main Bearing Help! - 09/20/10 01:04 AM

Did you check the caps to make sure they fit tightly in the groves? If one is loose, it may be cocking sideways a little. Just a thought.

Posted By: Cab_Burge

Re: Main Bearing Help! - 09/20/10 02:07 AM

Quote:

Have you check the run out or can you check the run out

Posted By: chris3

Re: Main Bearing Help! - 09/20/10 03:36 AM

Cab, I was not ignoring your comment. I do appreciate all of the help with this problem. The machine shop has listed on the work order checking the crankshaft for straightness, turning both main and rod journals, polishing and balancing the crankshaft. The crankshaft is still laying in the block and I will set-up and check the run out.

As I had posted earlier when micing the crankshaft all of the journals are less than .001 different from end to end so I think the machine shop did a good job checking and finishing the crankshaft. Again thanks to all for all of the suggestions.

Posted By: Cab_Burge

Re: Main Bearing Help! - 09/20/10 03:52 AM

There is only a cuople of reasons the crank won't turn, there's not enough clearnances on either the main bearings or the thrust clearnance or the crank is bent

I would start at the front of the block and tighten #1 main cap down at a time and see if the crank will rotate, if not remove it and do #2 and then # 3 and so on. If the crank won't turn with any of the caps tight you may have a main web bore needing align honing or align boring as a result of the block being out of alignment on the mains. Over heating the block can cause this, usually the main caps will not have any inteference fit in the block if that happens

Do your main caps fit loosely or do you have to tap them into place or use the bolts to make them fit into the main saddles ? BTW, when it comes to assembling and blueprinting motors everything has to be checked, every machine shop and machinest as well as mechanics makes mistakes, it is the engine assemblers job to find the mistakes and get them corrected before the motor is ran the first time

your being tested on this one, you can and will figure it out

Let us know what you find and what it takes to fix it

Posted By: chris3

Re: Main Bearing Help! - 09/20/10 01:55 PM

The main caps do not just sit down in the block. You have to give them just a slight tap and they will go in place.

With no main caps installed the crank will turn free. I installed the #1 cap, torqued it down and the crank would not turn. Took that cap off and installed the #2 cap and it would not turn. Did this to every single cap and the crank would not turn. Crank will not turn with any cap in place.

Removed the #3 main thrust bearing and cap. Set the crank in place. Crank will turn free. Install #1 cap and torque it down and the crank will not turn.

I will check the run out on the crankshaft tonight; however, I believe that I will have to have this motor align honed to get this right.

Yes we will get it fix; however, it has cost us another week-end. If we had not already spent so much money on this block, I would have set it aside and worked on another. Thanks for all of the help MOPARTS and if anyone has any ideas please let me know.

Posted By: Performance Only

Re: Main Bearing Help! - 09/20/10 02:42 PM

put the crank in the block and torque main caps 1,2,4 and 5
install #3 cap without the lower shell and torque it. see if the crank spins freely. i'm guessing it will.

Posted By: Crizila

Re: Main Bearing Help! - 09/20/10 02:53 PM

Dumb question at this point, but did you mike the bearing shells to make sure they are actually 10 over?

Posted By: sleepyhead416

Re: Main Bearing Help! - 09/20/10 03:21 PM

Dumber ? Do u have mains on right? Tangs facing one another.Also when I use studs I drill main caps 1 size bigger.

Posted By: quick77rt

Re: Main Bearing Help! - 09/20/10 03:23 PM

A long shot? Has the block ever been align bored?

If so you might check the bearing tangs to see if they are now too big to let the bearing sit right in the block.

I had the no turn problem, I made it turn, pulled the crank, seen the two areas it was tight, used a small file on the bearing half just a bit, installed the crank with no further issues.

Posted By: chris3

Re: Main Bearing Help! - 09/20/10 05:13 PM

Tried everything except line honing. May be next. Most racing machine shops are busy until after Oct. 1 for the Civil Wars race.

Posted By: abodiesonly1

Re: Main Bearing Help! - 09/20/10 05:39 PM

Quote:

The main caps do not just sit down in the block. You have to give them just a slight tap and they will go in place.

With no main caps installed the crank will turn free. I installed the #1 cap, torqued it down and the crank would not turn. Took that cap off and installed the #2 cap and it would not turn. Did this to every single cap and the crank would not turn. Crank will not turn with any cap in place.

Removed the #3 main thrust bearing and cap. Set the crank in place. Crank will turn free. Install #1 cap and torque it down and the crank will not turn.

I will check the run out on the crankshaft tonight; however, I believe that I will have to have this motor align honed to get this right.

Yes we will get it fix; however, it has cost us another week-end. If we had not already spent so much money on this block, I would have set it aside and worked on another. Thanks for all of the help MOPARTS and if anyone has any ideas please let me know.

With the crank in place, and only 1 cap installed and torqued, it has to be a bearing problem.

Posted By: chris3

Re: Main Bearing Help! - 09/21/10 03:25 AM

Okay, we are back with more information. Tonight we took the new bearings out. Cleaned up and installed the the old .020 bearings. Cleaned up the old damaged crankshaft. Keep in mind we broke two rods and did not damage any main bearing journals. Put the old crank in the block, installed the #1 and #4 main bearing cap, with the old .020 bearing in the cap. The crankshaft turned very smooth even on the old metal laden bearings. Possibly means that the mains do not have to be honed again.

New crankshaft is tomorrow back to the machine shop to have the crankshaft and all of the work that was paid for checked to see if it was done right. If this all checks out then we may be buying another set of bearings. As I promised I will keep everyone up to date on what actually turns out to be the problem. Thanks again for everyones help. This has been an experience.

Posted By: chris3

Re: Main Bearing Help! - 09/21/10 01:14 PM

Posted By: Cab_Burge

Re: Main Bearing Help! - 09/21/10 06:09 PM

Quote:

Inquiring minds want to know

Posted By: chris3

Re: Main Bearing Help! - 09/21/10 06:37 PM

Cab, here is the latest. Carried the crankshaft to a machine shop, I stood and watched the crankshaft be checked, the crankshaft is as straight as any crankshaft can get. Checked the dimensions of the journals and they are all dead on. All of this leaves only one thing and that is something to do with the bearings. Thanks for all of you thoughts and help. We it is actually complete I will let everyone know what happened.

Posted By: chris3

Re: Main Bearing Help! - 09/23/10 03:53 PM

Up-date. Removed the main bearings. Installed the #1 main cap and torqued. Measured the inside diameter, block and cap. Top to bottom was correct. Side to side was slightly off little tighter. Diagonal measured .005 too tight. #2 cap top to bottom was correct side to side slightly off with a difference,slight to nail touch, at the parting lines of cap to block. Diagonal measurement of too tight. For some reason diagonal dimension of the caps are too tight when torqued.

Posted By: Cab_Burge

Re: Main Bearing Help! - 09/23/10 05:22 PM

Sounds like it is time for a align hone(not a align bore

) That is a good find

Knowlege is the solution to finding the source and cure for problems

Posted By: Crizila

Re: Main Bearing Help! - 09/23/10 08:31 PM

Quote:

Up-date. Removed the main bearings. Installed the #1 main cap and torqued. Measured the inside diameter, block and cap. Top to bottom was correct. Side to side was slightly off little tighter. Diagonal measured .005 too tight. #2 cap top to bottom was correct side to side slightly off with a difference,slight to nail touch, at the parting lines of cap to block. Diagonal measurement of too tight. For some reason diagonal dimension of the caps are too tight when torqued.

Any ideas on how it got that way?

Posted By: chris3

Re: Main Bearing Help! - 09/23/10 08:47 PM

Have not got a clue what would cause this. I have been measuring, calculating, change and re-checking this block for 2 1/2 weeks trying to get the crankshaft to turn in a block that by all calculations should have had 2 1/2 thousandths clearance. When the crank and mains were first installed and "plasigage" was used it measured 2 1/2 thousandths. Problem is the crankshaft will not turn. Took everything, including the block, to a machine shop this morning. Crankshaft was re-checked, bearings were re-measured and then we go to the block as I said previously when we measured vertically we were back to square one that should have been perfect. Measured horizontally in the block, slightly less clearance, but it still would have clearance and should turn. Measured diagonally and the block was .005 less than the other two directions. Mains do have studs; however, the caps slip down easily and will lock in place with just pressure from the palm of your hand. To clean this up means I need to get 2 1/2 thousandths on each side on the diagonal.

Posted By: Performance Only

Re: Main Bearing Help! - 09/24/10 01:32 AM

Quote:

Sounds like it is time for a align hone(not a align bore ) That is a good find Knowlege is the solution to finding the source and cure for problems

what's your reasoning for suggesting that? align boring is the best way to ensure perfectly round bores. if the OP really has .005 too tight diagonally and not .0005, boring would be my first choice. if it's only .0005, honing would be fine.

Posted By: chris3

Re: Main Bearing Help! - 10/11/10 02:31 PM

Want to update and thank eveyone who offered opinions concerning the main caps. The final problem has not yet been determined. I got out another block, everything checked out fine. The new motor is assembled, in the car and cranked yesterday. Leaving Tuesday going to Z-Max and it's first run down the track will be Tuesday night. Thanks again for all of the help from Moparts members.