Author Topic: Shims big End shells ???  (Read 3461 times)

Offline Marqs1979

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Shims big End shells ???
« on: 14.01. 2014 15:38 »
Hello!

Is this an ok and reasonably good way to reduce shell??
I found these shims between the connecting rod and shells: (
I suppose you think I'll let grind the shaft instead.

Or?

http://forumbilder.se/DBJ0O/20140114-160938.jpg
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Online RichardL

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Re: Shims big End shells ???
« Reply #1 on: 14.01. 2014 16:40 »
I was about to say, "Absolutely not", but then I came across this:  http://deckwartaperedshims.com/main-bearing-shims-product-info.php

Not saying this should be your first choice, but it does suggest that an option is possible. The problem with the shim used by previous owner is that, to do anything, it requires filing off the ends of the bearing. This probably left an egg-shaped hole for the crank to fit in and, I think, leading to rapid wear on the bearings 90 degrees from the parting line. For the sake of good engine rebuilding, I'd say, don't repeat it.

Regarding your rods, as I was admonished to do so by a friendly forum member, all those knicks should be polished out.

Richard L.
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Re: Shims big End shells ???
« Reply #2 on: 14.01. 2014 19:04 »
Using shims would be a LAST resort. Get the crank ground and new slippers to match. Check the rod big end bore for size and out of round, they can be re-claimed.
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Offline bikerbob

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Re: Shims big End shells ???
« Reply #3 on: 14.01. 2014 19:52 »
Shimming the the shells is nothing new I did it about 50 years ago on an old car what you did was you put a shim behind the shell tightened the bolts up and then turned the engine over using the starting handle then took the shells out and scraped off the high spots in fact the shimming was not metal it was brown paper. It worked and I used that car for a number of years without any problems. But what you have to remember was in those days the white metal on the shells was a lot thicker then, I would not do it now because the thickness of the white metal is very thin you would go straight through the white metal a regrind is what is needed
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Online RichardL

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Re: Shims big End shells ???
« Reply #4 on: 14.01. 2014 21:05 »
P.S.   ...and rod bolts replaced.
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Offline A10Boy

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Re: Shims big End shells ???
« Reply #5 on: 14.01. 2014 22:32 »
NO! Never ever! Crankpins wear oval so there will always be a tight spot or tight / slack situation going on with this bodge.
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Re: Shims big End shells ???
« Reply #6 on: 15.01. 2014 13:07 »
Mine are shimmed in my 61 and has been working well.  It was that way when I tore it down, so I went back with them.  Very thin brass shims.  I don't push the engine hard, so maybe that's why I'm getting away with it.  Given a good machinist (hard to find here in the sticks) I would have the crank ground and fit new shells next time.
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Offline isuzu

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Re: Shims big End shells ???
« Reply #7 on: 15.01. 2014 15:30 »
I did this trick also to get things just a bit more tight with new shells on a reasonable crank with car engines (using plasticine if you are uncertain).
I used sigarette paper instead of the copper strips mentioned earlier in this thread. Next time you open the engine you will see the paper in just the same state as you have put it in years ago!
Works great.
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Offline Marqs1979

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Re: Shims big End shells ???
« Reply #8 on: 15.01. 2014 18:44 »
Is it possible to grind the crankshaft without taking it apart? Can you use crankshaft sludge trap for studs to get the middle of the shaft?
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Re: Shims big End shells ???
« Reply #9 on: 15.01. 2014 19:19 »
Well it seems that bodge is a lot more prevalent than I thought.
The crank can be ground with the flywheel still attached, if that's what you mean Marqs.
Not sure what you mean about sludge trap.
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Offline Marqs1979

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Re: Shims big End shells ???
« Reply #10 on: 15.01. 2014 19:51 »
No. 3 ice Sludge trap plug

But I do not think it's the right approach.


http://www.draganfly.co.uk/images/shop/b3/10/10_a_group.gif
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Offline A10Boy

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Re: Shims big End shells ???
« Reply #11 on: 15.01. 2014 20:43 »
Over the years I've found some right bodges in engines and I often wondered what kind of butcher would do such a thing, well now I know.......
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Re: Shims big End shells ???
« Reply #12 on: 15.01. 2014 21:24 »
Ouch?!
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Re: Shims big End shells ???
« Reply #13 on: 16.01. 2014 07:05 »
Marqs, crank grinders set up off the main shaft and dial in for the correct stroke (they should). The plug can stay in but must be removed and cleaned out after the grind.
Anyone that has had shims in there is advised to have the big end hole of the rod checked for size and round. The rods don't need another excuse to see daylight *eek*.
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Offline JulianM

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Re: Shims big End shells ???
« Reply #14 on: 16.01. 2014 08:07 »
Just because it is wide spread and kits sold, it does not mean it is a good thing.

At the end of the day it's a bodge to get away with not being able to do the job properly.

There are reasons...
No money and need to get to work on Monday,
Live in the outer Hebrides and have no suppliers.
Etc.

But outside these extremes you should try to push for perfection and to do the job ONCE and do it WELL.

Think like this.
If you were paying an engineering company to rebuild your engine. "what would you like the finished engine to be like?" (money not being the question)

Happy New Year to you all.
Julian 
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