Conrod shell sizes

[Non MemberParticipant]

Hello, I’m new to the club and to Traction Avant ownership.  I live in France and have a 1954 11BL.

I’ve decided (courtesy of some lower end noises from the engine) to remove the engine and modify the conrods with later 11D ones that have replaceable shells.  Motor now out and dismantled, crankshaft checked over.

You’d have thought, being here in France, that I’d easily find the info I need.  Sadly, whilst my French is pretty good, wandering into technical territory gets a little trickier.

So, the crankshaft is true and in reasonable condition.  The bearings measure at 48mm for the conrods and 50mm for the main bearings (give or take a few hundredths).

I then go to buy new conrods and shells.  They are “standard”, +0.25, +0.5 etc etc.  What does that mean?!  Is 48mm/50mm the standard?  I’ve tried to look up crankshaft data, but there seems to be a lot of variety.

Help please from anyone who knows, or knows how I find out, what size of shells I need.

Many thanks in advance.

Jonathan Fitton

[Roger GrixParticipant]

Hi Jonathan,

Sorry, I can’t help with bearing sizes (but someone will be able to).  I just wondered where in France you are living.  We have a house SW of Toulouse where we spend about half of the year.

Roger

[Non MemberParticipant]

Hello Roger,

We’re about three and a quarter hours NW of Toulouse, between Bordeaux and Angoulême.  I’m guessing that puts us somewhat distant from you.  However, if we head down your way, our if you’re travelling South from the ferry for example, then a meet-up would be very nice.

Best wishes,

Jonathan

[Patrick Russell-JonesParticipant]

Hi Jonathan

Check the Jose Franssen page for crankshaft. 0=50mm for the original crankshaft.

Patrick

[David FaulknerParticipant]

From CTA Service Bulletin:

Crankshaft

Main bearing: 50.00 mm std.

Con Rod Crank Pin 47.990-48.000 mm

Main bearing Radial Play: 0.04-0.08 mm

Con Rod Radial Play: 0.10-0.15 mm

Measure the axial play from the rear bearing at transmission chain.

So yes Jonathan 48/50 mm is standard.

If you do need the crank reground then look for someone with an old ‘Prince’ grinder as it can do the journals individually, modern machines can only do all the same size apparently.

Where it matters is that being done individually the minimum (within tolerance) can be taken from each one leaving more ‘meat’ for potential future renovations.

Good luck with the search.

BTW Traction Universelle 50th Rally is at Magny-Cour next week (10th-12th) so you may be able to pick up some parts there as there will be a jumble and some traders on site. (I have a list of things to look for 🙂 )

• This reply was modified 7 years ago by David Faulkner.

[Non MemberParticipant]

Gentlemen, many thanks.  I’m grateful for the information and advice.

[Author]

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