Conrod small end bushes

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Conrod small end bushes

Postby Asolepius » Wed Aug 19, 2015 5:53 am

My 998cc has 1098 rods and a few years back one of the small end bushes started rattling. It seems to be impossible to buy the bushes so I had to press one out of a spare rod and use that (my rods are lightened so I can't change them now). Now one or more of the other small ends are rattling. This time I would rather have a new bush reamed to the correct size - the rods are over 50 years old of course. I can make the bush on the lathe and use a hand reamer, but what is the correct material? Some kind of bronze I'm sure, but would Oilite be OK?
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Re: Conrod small end bushes

Postby Charlie Tolman » Thu Aug 20, 2015 12:32 am

Victoria British might still have a "piston pin bushing set" (four pieces), with their part number of 1-395.

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Re: Conrod small end bushes

Postby Asolepius » Thu Aug 20, 2015 11:07 am

Just found they have come back into stock at AH Spares in UK. Only GBP1.70 each!
Les Rose, Salisbury, UK
1959 Sprite, owned since 1978
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Re: Conrod small end bushes

Postby Asolepius » Sat Aug 22, 2015 7:32 am

OK the new bushes have arrived. I was just looking at the BMC service manual which says:

"The piston/gudgeon pin and connecting rod/small end bush can only be obtained as assemblies. Therefore, under no circumstances should the small end bush or gudgeon pin be renewed separately".

This is rather unclear - renewed separately from what? From each other or from the rod or piston? I can't see any problem if the bush is properly honed to fit whatever pin you have. What does this mean?
Les Rose, Salisbury, UK
1959 Sprite, owned since 1978
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Re: Conrod small end bushes

Postby Sprite33 » Tue Aug 25, 2015 1:57 pm

I am not sure why they say that. I have replace them on my 1098 race engines periodically. The shop that resizes the big end installs them and hones the bushings to size to fit a wrist pin that I supply them.

They must be honed precisely square to the rod as is the big end. That statement is probably precautionary so no one just slaps new bushings in that are not sized to the wrist pin or honed improperly resulting in problems later.
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Re: Conrod small end bushes

Postby Joe Schlosser » Mon Sep 28, 2015 10:33 am

The language of the warning seem that you need to do all 4 bushed together. Never one and leave the other three. The big trick is making sure that they are honed square.
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Re: Conrod small end bushes

Postby Asolepius » Sat Jan 06, 2018 7:15 am

Medium term follow up to this thread, but so far the outcome is good. I bought a 5/8" hand reamer and did them myself. Very tough job, each one took 40 minutes to ream. The taper on the reamer seemed to ensure that it stayed square to the rod. It took 3 passes to get the right clearance - the first 2 left it too tight. The rattling has gone, and I have done 1100 miles since. Keeping fingers crossed!
Les Rose, Salisbury, UK
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