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big end bearing shims


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  #1  
Old 07-19-2019, 07:36:00 AM
sunshineman sunshineman is offline
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Default big end bearing shims

Hi all
What is the obsession with shims?
Many engines I encounter have more shims then required, hence huge cleareance.
Example rebuilding a 3hp sunshine for a mate that did not go.
This was an engine my mate bought as a fully reconditioned engine.
Granted it has a nice new bore , engine shop ground crankshaft , new big end bearing but about a dozen shims so it has about three sixteens cleareance.WHY ?
This one of many I have seen
Don't shim unless required,
Many of my engines with new bearings have no shims at all, bored the bearing to suit crank
Regards sunshineman
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  #2  
Old 07-19-2019, 07:56:20 AM
cobbadog cobbadog is offline
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Default Re: big end bearing shims

Silly me! I thought you were talking about 'cross dressers'at first


If an engine has been rebuilt why would it have such a big clearance of 3/16", that is huge.
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  #3  
Old 07-19-2019, 07:57:06 AM
karragullengine karragullengine is offline
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Default Re: big end bearing shims

3/16 clearance is huge, something sounds wrong there, I've never come across a bearing shimmed like that.
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Old 07-19-2019, 08:25:22 AM
Paul Richardson Paul Richardson is offline
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Default Re: big end bearing shims

A bearing might be considered well and truly flogged out having much less clearance than an eighth,especially a bigend?
If the bearing is new,then somebody knows nothing about what he is supposed to be doing.
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Old 07-19-2019, 09:16:49 AM
sunshineman sunshineman is offline
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Default Re: big end bearing shims

The point I making is it has been shimed and the result is 3/16 cleareance .
WHY put the shims in ? Clearly they do not belong !
You measure the shaft with a micrometer , you measure the inside diameter of the bearing and work out your cleareance, shim if required , throw whats left over in the bin .But many so called engine builders put more in for some strange reason defeating the purpose of new bearing and fresh shaft grind .
I have seen it time and time again.
Sunshineman

---------- Post added at 08:16:49 AM ---------- Previous post was at 08:01:21 AM ----------

Maybe I should document with photos some of the repairs I see.
Bores being honed is another - trying to hone out the lip , I have a wolsely barrel that was fitted to an engine with 20 thou taper in the bore , no longer round .That the previous owner honed thinking this would remedy the wear-just made it worse
I sleeved it to standard
Sunshineman
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Old 07-19-2019, 06:12:12 PM
Scotty 2 Scotty 2 is offline
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Default Re: big end bearing shims

Quote:
Originally Posted by sunshineman View Post
you measure the inside diameter of the bearing and work out your cleareance, shim if required , throw whats left over in the bin .
As long as it's the spare parts bin. Making those suckers is one of my hate jobs
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Old 07-19-2019, 06:22:08 PM
Andrew Mackey Andrew Mackey is offline
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Exclamation Re: big end bearing shims

I could write a book on the crazyrepairs I have seen over 60 years of working on engines! Some of the stuff is absolutely unbelieveable, the things people do. People who are not mechanically inclined should keep their hands off, but no, they have to mess with something, just because it's there

Things like excessive valve clearances, excess shims, bearindsset so tightthey melt, you name it I have seen it Some 'farmer fixs' are get by deals, like using pieces of oak for main bearings, a leather belt for a con rod big end bearing (found that one in a madel T), nedle bearings put in a con rod with a bunch of grease (didnt last long with no race). You never know what you will find out there!
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Old 07-19-2019, 09:10:21 PM
sunshineman sunshineman is offline
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Default Re: big end bearing shims

Andrew ,
Exactly what I'm saying.
Regards sunshineman
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Old 07-19-2019, 09:38:38 PM
Inter Bloke Inter Bloke is offline
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Default Re: big end bearing shims

[QUOTE=Andrew Mackey;1590358]I could write a book on the crazyrepairs I have seen over 60 years of working on engines! Some of the stuff is absolutely unbelieveable, the things people do. leather belt for a con rod big end


My family actually "worked" a small Fairbanks Morse on a leather bigend through some of the depression and then all the war years. It would pump three tanks of water to a leather insert and then be replaced with a piece of oil soaked leather harvester belt for the next three.

One of the strangest shim arrangements I have seen was an Alamo walking beam engines main bearings with wooden shims ! It looks like a local engineer came up with a system when he remetaled the bearing that you just tighten the cap down and crush the wooden wafer to size until you have the clearance you want. It had lock nuts on the studs to keep the cap in place, and had been working for decades so who can say it shouldn't be done that way ! When it gets rebuilt ( its now mine) it will have the shims done properly !
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Old 07-19-2019, 10:17:36 PM
Cockie Cockie is offline
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Default Re: big end bearing shims

I've just lifted the main bearing caps on my 2hp KA Cooper /Stover as it had bearing slop and found it has badly scored journals. Yes it was shimmed, but the shims were on opposite sides, one on the piston side, one on the back. I would have thought if needed they should be on the same side. Looking now of getting the journals sprayed and machined, and fitting new bearings.
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  #11  
Old 07-20-2019, 01:06:06 AM
sunshineman sunshineman is offline
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Default Re: big end bearing shims

Mr inter bloke
Repairs in the bush are to keep a vital piece of equipment in operation. Nothing to do with what I'm saying.
Example again why get an engine shop to grind the big end journal on the crankshaft then manufacture and bore a bearing to suit, then to have some hobbyist to shim up this work to give it ridiculous cleareance , defeats the whole purpose of the work just carried out.I ask again why - the obsession of having to have shims regardless of need.
Regards sunshineman
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  #12  
Old 07-20-2019, 02:44:16 AM
cobbadog cobbadog is offline
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Default Re: big end bearing shims

Well it certainly would make for some interesting reading sunshineman if you would like to start a thread on such stuff ups.
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Old 07-20-2019, 02:52:45 AM
Scotty 2 Scotty 2 is offline
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Default Re: big end bearing shims

Quote:
Originally Posted by sunshineman View Post
I ask again why - the obsession of having to have shims regardless of need.
Regards sunshineman
Life is a continual learning curve. We were not born knowing everything. Luckily most people learn things as they go along.
My Pop used to tell me that you should learn something new every day otherwise it's a lose of a day.
I know you've taught me stuff I had no idea about Hilton. An awful lot.

Cheers Scott
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Old 07-20-2019, 03:58:18 AM
Darryl Darryl is offline
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Default Re: big end bearing shims

Quote:
Originally Posted by sunshineman View Post
Mr inter bloke
Repairs in the bush are to keep a vital piece of equipment in operation. Nothing to do with what I'm saying.
Example again why get an engine shop to grind the big end journal on the crankshaft then manufacture and bore a bearing to suit, then to have some hobbyist to shim up this work to give it ridiculous cleareance , defeats the whole purpose of the work just carried out.I ask again why - the obsession of having to have shims regardless of need.
Regards sunshineman
Maybe he was using real thick oil 😊
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Old 07-20-2019, 03:59:18 AM
crashley crashley is offline
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Default Re: big end bearing shims

When my A model ford engine was rebuilt they machined the crank and then put a set of shims in place like these "Complete Set of laminated shims, 2 for rear main, 4 for front and center main bearings. 6 layers per shim - each layer is .002 thick."
and then bored the bearings to suit
This means that when the bearings wear you just have to remove a shim or 2 and you are back in business
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  #16  
Old 07-20-2019, 05:09:01 AM
sunshineman sunshineman is offline
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Default Re: big end bearing shims

Mr crashely,
Correct if bearing bore matches cranksize with correct cleareance, but fitting shims because you have a draw full makes no sense.

Scotty maybe just maybe some people don't listen to correct information.
I was taught as you were learn everyday at least one bit of information.
I have been involved in the automotive engine reconditioning industry 40 plus years and still learning, some days are a real challange.
Kind regards sunshineman
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Old 07-20-2019, 07:41:52 AM
cobbadog cobbadog is offline
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Default Re: big end bearing shims

I enjoy learning new things each day but remembering them is starting t get tricky. I was doing a job, soldering the D.B. fuel tank up after sand blasting found some pin holes, and I was having a moment trying to think how to do what I wanted to do then , Pa tapped me on the shoulder and reminded. I still wish he was still here but he is not forgotten.
The lesson from today is to make sure the diameter of the rod is correct before bending it to shape and wanting to put a thread on it and also finding out that the die is stuffed. So I have learnt tomorrows lesson in advance and will buy a new 1/4W x 20 tpi on Monday and start again.
Will have a break tomorrow due to a shortage of a certain die and to take Dee out for her birthday treat but must do my BAS in the morning and send it off before the taxman knocks on the door.
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