Author Topic: CS 3-1 big end bearings  (Read 217 times)

hugh54

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CS 3-1 big end bearings
« on: December 30, 2022, 11:20:48 PM »
Hi,

I'm fitting new big end shells measuring the clearance with plastigauge, and was wondering if anyone has noticed new big end bearing shells spreading the cap fractionally making it difficult to fit the cap, particularly from underneath inside the crankcase. It was easy to fit with the old shells but with the new ones the cap goes as far as the shank of the bolt where the thread stops and then has to be tapped on to go any further. It makes it difficult when testing for clearance with a plastigauge. I would have to tap the bolts out to get it off.

It seems that the spread of the bearing spreads the cap a fraction.

Might have to try a bit of wet and dry on the bolts to polish them a bit perhaps.

Cheers


cobbadog

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Re: CS 3-1 big end bearings
« Reply #1 on: December 31, 2022, 10:18:29 AM »
I would have a chat to your supplier and see what they make of it. Sometimes manufacture can stuff up and not be aware of it. I had a problem with one part for the David Brown and all the parts came from the UK. I asked why was that part different. He replied overnight (emails) and asked for a photo, Send that and he replied that he went through the parts bin and every one of them was made wrong. He quickly had the right one made and air freighted to me with an appology. I replied no need for the appology, a problem was found and you corrected it super quick. From time of identifying the problem to replacment part at the post office, 7 days.
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38ac

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Re: CS 3-1 big end bearings
« Reply #2 on: December 31, 2022, 12:52:03 PM »
As Cobbadog said there could be an issue with the new bearing but I have run into same deal with both CS and Listeroids several times. A tight side big end bore and a large side insert will do it. Many times Ive had to tap the bolts up to remove the cap. An old insert will be deformed by the loading and fall out of the rod or cap while a new set properly fitted should require a light tap or two to seat it, any more than that and you have a parts problem. Do not sand down the bolts. The shanks are what pilots the cap to the rod and you do not want to disturb that fit. 
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cobbadog

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Re: CS 3-1 big end bearings
« Reply #3 on: January 01, 2023, 02:23:58 AM »
38c, my supplier, Old Timer Engines in Queensland says that he does have a big end bearing for my engine but he cannot put his hands on it quite yet. Reason being is that he bought out another supplier and all the stock was itemised but is not unpacked. His price was AU$255.00 + postage
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38ac

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Re: CS 3-1 big end bearings
« Reply #4 on: January 01, 2023, 02:21:03 PM »
Cobba,
There are 2 sizes of big end bearings for 3/1. The early ones had a smaller crank pin than a 6/1. Later ones use the same big end bearing as a 6/1. Im guessing his 255 bearing is the early one as they are very tough to find.
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sirpedrosa

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Re: CS 3-1 big end bearings
« Reply #5 on: January 01, 2023, 03:17:35 PM »
Cobba, Butch

I think 3/1's are (early ones) unobtanium parts... and if Bambords, they are all of that kind.

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hugh54

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Re: CS 3-1 big end bearings
« Reply #6 on: January 15, 2023, 06:27:20 AM »
Thanks for the responses. I've decided to go with the original bearings as there is nothing wrong with them. With a plastigauge they have .002". I only pulled it down to check the bore to see why it was blowing smoke.

I figured reassembly was going to be easier by partially fitting the piston up into to the bore from the bottom so that the rings were just inside, while the block was on the bench. Then fit the rod to the piston and push the piston all the way up into the bore. Then turn it over lower the whole lot down onto the studs. 

Trouble is doing it this way is that it makes it impossible to get to the bearing cap bolts from the top after the block is fitted. So with the new bearings spreading the cap fractionally, when the bearing cap is tapped up into place it pushes the bolts up, and not being able to get to the bolts from the top, it's impossible to tap them back down.

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