C15 early model plain big end conversion to later roller type

[rhyatt]

Is this feasible and perhaps desirable/beneficial please?

[TTJOHN]

I think it could be done, depending on how much meat you've got on the cases, however saying that, why change something that has been okay since the C15 was developed? The alternative is buy a C15G model if you can find one.

TTJ

[rhyatt]

So are you saying that it is not just a change of con rod with bush to con rod with rollers, but peripheral changes to crankcases etc.
My big end bush has failed so I need to replace it , just thinking of the later roller assembly as in my later ss80

[TTJOHN]

Sorry Rhyatt. I misread what you put, I was thinking you meant to change the crank bearing.
I believe I have a new old stock con rod with big end, complete, somewhere in the shed, I'll have a look and let you know.

TTJ

[rhyatt]

Thank you,
I've yet to strip/split the engine but have discovered that the rod barely rotates around the crankpin.
It was a new assembly 500 miles ago , but maybe the current seized bush was tight on tolerance in the 1st place.
I've had copious amount of oil everywhere inside the engine , so unknown why it tightened up other than minimum tolerance.
If it's a relatively straightforward job to put a roller rod and crankpin in place of a bush /pin , then I'd prefer that if possible. The crank has to be split either way.
Cheers

[Rupert]

Alpha do a needle roller bearing as a straight swap for the plain bush big end in your crank/rod, but it isn't much better than the plain bush as there isn't space in the rod for a bigger assembly.
Best option is to fit a steel flywheel crank with 41-234 rod from a 1964 onward C15 as that has a decent size roller bearing big end.
C15 cranks are all interchangeable into all crankcases prior to C15G engine introduction in late '66 without modification to crankcases.

[rhyatt]

Thank you for the explanation.
So I need 1 later crank half complete with a  newer roller bearing 41-234 roller rod pressed into the original other flywheel half.
Failing finding these bits ,replace with original bush into my original crank assembly
Thank you

[Stubaker58]

Hi Richard

I have just such a later crank assembly on the shelf in the garage!
I can post it to you for you to assess if you like, it feels pretty good to me. Of course you may still want to split it.

It's leftover from my B40 build. I got as far as cleaning out the sludge trap and bolting up the cases before it dawned on me that it was for a C15 not a B40.(The gudgeon pin wouldn't fit).

Doh!!

PM me the address if you're interested.

Regards.

[Rupert]

Thank you for the explanation.
So I need 1 later crank half complete with a  newer roller bearing 41-234 roller rod pressed into the original other flywheel half.
Failing finding these bits ,replace with original bush into my original crank assembly
Thank you

You need both steel flywheels as you must have a matched pair. And in this instance the later crankpin shank (1" diameter) won't fit the hole in the early cast iron flywheel (15/16" diameter).

[rhyatt]

Thank you all for various comments.
I'll be buying a clutch extractor for that part of the job , but as far as the timing side pinion , is it just a 2 jaw puller or are there any more special tools needed please?
Reading the various service sheets , it looks like --- distributor out - oil pump out -- pinion and drive gear out and then crank out.
Any particular tricks gratefully received.
I've been exploring sheets 421,422,423,424 and haven't seen anything about end float yet.
Is this automatically obtained when crank is assembled , it looks like the crank is pulled hard into timing side by pinions etc
Many thanks

[Stubaker58]

The crank should be a very tight fit in the primary side bearing. A special puller may be needed for removal/refitting.
Endfloat is not really present when the engine is fully built as the crank is held tight in that primary side bearing BUT there needs to be clearance, something around 4thou to allow for expansion.
Measuring it is described in RR vol 1.

[rhyatt]

Thank you