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Rod Bearing Clearance

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1 month 2 weeks ago #231074 by kittylover123
Replied by kittylover123 on topic Rod Bearing Clearance
i texted my engine guy (master machinist, fabricator, you name it) he says yes very common for crank journals to be outta round, i didn't know that...
-i never disregard his opinion....he drives a pro-mod that has run 5's...so it's gospel to me

-i suppose you could get away with more clearance with your used bearings...and usually on the loose side does not hurt things...even with high rpm motors
-but nothing beats good machining....round bores, round journals, flat decks..etc

Caterpillar D6C 99j

Tax me, I'm Canadian:canada:

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1 month 2 weeks ago #231089 by sheddcanyon
Replied by sheddcanyon on topic Rod Bearing Clearance
"-but nothing beats good machining....round bores, round journals, flat decks..etc"

Agreed! And I might end up doing that. I'm going to fit up the used bearings and plasti-gauge at different points on the journal. If clearance and variation aren't too crazy, I'm going with the old ones.

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1 month 2 weeks ago #231112 by trainzkid88
Replied by trainzkid88 on topic Rod Bearing Clearance
dont reuse old bearings because if they are damaged in some way and it can be hard to tell.
it just costs more money and time to fix. yes a get it running to get home repair is one thing. but do it properly and quite possibly never touch it again.

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1 month 2 weeks ago #231114 by PhilC
Replied by PhilC on topic Rod Bearing Clearance

dont reuse old bearings because if they are damaged in some way and it can be hard to tell.
 

The bearings in the D4600 are not the same as modern steel backed shell bearings. They are some form of aluminium alloy and they are at least 1/4 thick. The only problem I can see with using the bearings again is the fact that the crankshaft journals have been polished. Keep in mind that these engines are not high revving and only very low horsepower for their size.

sheddcanyon
Can you tell me where you got your new bearings from? I have two D4600's that are in need of a full set of non-standard bearings.

Regards

Phil

944A - Machine SN 43A2589 Engine SN 90A284
955K- Machine SN 71J3772 Engine SN 83Z0704
D6 SN's 4R732sp, 5R2724, 5R4832
D8 SN's 15A1254, 15A2287, 15A2723

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1 month 2 weeks ago #231119 by sheddcanyon
Replied by sheddcanyon on topic Rod Bearing Clearance
Phil, I got the bearings through Florin Tractor. They are after market, made in Austria. Dana was also able to get me main bearings, .030" under, which coincidentally had the right clearance, at least according to plasti-gauge.

After looking closely at my used rod bearings last night, I'm pretty sure I'm going to have to get the crank turned. Some of the used bearings look new, others are a little grooved and scuffed. I'm going to measure the new bearings inside the rod end with an inside mic tonight and see where they come out. In hindsight, maybe I should have done all this measuring prior to assembling. But when you are installing brand new bearings and your crank measures within spec........

I went through the effort of getting new bearings to zero-time the rotating assembly. As I think things through, it would be pretty stupid to do all this work to the bottom, re-do the heads, etc., and then throw sketchy rod bearings back in.
The following user(s) said Thank You: edb

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1 month 2 weeks ago #231121 by kittylover123
Replied by kittylover123 on topic Rod Bearing Clearance
trainzkid is right, do it correctly, once, and forget about it....

another thing about bearing shells is they must have crush, so they fit snugly in their bores..

Caterpillar D6C 99j

Tax me, I'm Canadian:canada:

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1 month 2 weeks ago #231123 by PhilC
Replied by PhilC on topic Rod Bearing Clearance
Ok. I have been repairing diesel engines for over 30 years. I have over this time reused bearings many many times and not one has come back to bight me later on. One engine had the entire top end replaced including valves, pistons, rings,sleeves but the bearings looked like new and measured up as new. I even got an engine reconditioning company to double check and they came to the same conclusion. That engine is still going today and has added another 1500 hours to its life. Reasons for reusing bearings can be for time constraints, financial reasons, availability etc. Working for my father who worked hard all his life and never had a lot of money to spend on repairs you learn a lot about what can and can't be reused. I have even mixed bearing from different engines to get one working again.

As long as they are inspected and measured correctly then they should be able to be used again and as sheddcanyon said some are not looking so good.

Thanks sheddcanyon for the supplier info.

944A - Machine SN 43A2589 Engine SN 90A284
955K- Machine SN 71J3772 Engine SN 83Z0704
D6 SN's 4R732sp, 5R2724, 5R4832
D8 SN's 15A1254, 15A2287, 15A2723

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1 month 2 weeks ago #231135 by trainzkid88
Replied by trainzkid88 on topic Rod Bearing Clearance
yes ive heard of crank bearings being made out of leather soaked in neets foot oil smeared with grease and assembled they towed it while in gear around the block with a tractor to wear em in a bit till it could be cranked by hand and it ran for years. it was a old 26 chev. all sorts of things can be done and i have mixed an matched parts to get old stationary engines going again too. yes its not like we work them hard anymore as they are in retirement.

my point was if your going to the effort of doing everything else its not much more to do the lot.

has anyone thought perhaps these bearing are designed to be scraped to final clearance. it is possible

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1 month 2 weeks ago #231141 by oldbeek
Replied by oldbeek on topic Rod Bearing Clearance

Phil, I got the bearings through Florin Tractor. They are after market, made in Austria. Dana was also able to get me main bearings, .030" under, which coincidentally had the right clearance, at least according to plasti-gauge.

After looking closely at my used rod bearings last night, I'm pretty sure I'm going to have to get the crank turned. Some of the used bearings look new, others are a little grooved and scuffed. I'm going to measure the new bearings inside the rod end with an inside mic tonight and see where they come out. In hindsight, maybe I should have done all this measuring prior to assembling. But when you are installing brand new bearings and your crank measures within spec........

I went through the effort of getting new bearings to zero-time the rotating assembly. As I think things through, it would be pretty stupid to do all this work to the bottom, re-do the heads, etc., and then throw sketchy rod bearings back in.  Measuring the bearing bores in the torqued rods may tell you something.  A dial bore gauge may be better than a hand mic. It is easier to see the out of round.  I have no experience with all aluminum bearings so will not comment on how much clearance is needed with them. You mentioned the slight wear on the old bearings.  Your fingers can feel  .0005.   Do you have any specs on what the thickness of the bearing shell should be?


Cat 12 grader, 8T6995 running and restoring, Cat 12 grader 9K3585. parts machine, Adams leaning wheel Pull grader Mod # 22, ser#438

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1 month 1 week ago #231147 by edb
Replied by edb on topic Rod Bearing Clearance
Hi Team,
as an average if you measure the bearing thickness with a ball anvil micrometer or a caliper at the unworn section of the shell, near the split line, on all you good shells you should get as close as needed.
Each 0.030" undersized crank journal shell should be 0.015" thicker than a standard unit and so on.

Cheers,
Eddie B.

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