Guidance on choosing right connecting rod

[kirubt]

Dear All,

I need some advice/guidance on choosing the appropriate connecting rod for my car. 

Old/brown/rusted connecting is currently removed from my engine (Not in a useable condition)
Polished/good condition (6 Pieces) - Evaluating it for buying - Please guide is this suitable for my car (attached my mk1 model photo) 

Thanks
Kriu

[Robert Leigh]

The rods in your picture look to be the right ones, and they look as though they may have had some crack test fluid sprayed on the little end. This would be where any crack usually develops. If you buy these rods I suggest using new big end bolts and self locking nuts, which allow exactly the correct torque to be applied, and also new HT little end bolts. It may well be that the big ends require re-metalling to fit the journal size of your crankshaft. If they are too small it may be possible to machine to fit the shaft without re-metalling, or a skilled person could scrape them to fit.

[Chris KC]

I can't tell from the photograph, but some engines had 2 main bearings and some had 3.
If your engine has 2 main bearings the big end cap should be symmetrical around the fixing bolts; if 3 main bearings, the rods are offset to one side and slightly narrower (in fact it was same as 2-bearing rod, but a little cut off one side).

I wouldn't worry about a little surface rust, a wire brush can remove it, as long as there isn't other damage.

Cracks from the slot at the little end are a problem and to be avoided. If you don't have crack test kit look very carefully with a magnifying glass.

The other thing to avoid is any rod with cuts in the side of the shaft, sometimes people used to mark no's 1, 2, 3,4 by saw cuts in the side, it's a complete disaster...

[kirubt]

Hi Chris,

thanks a lot for your response. My car is 2 bearing engine. I see A7 components has a connecting rod (Item number - BC67) do you think that suits for my car?

Austin 7 Spares at A7 Components, the Austin Seven Specialists

Thanks
Kiru

[Chris KC]

Hi Chris,

thanks a lot for your response. My car is 2 bearing engine. I see A7 components has a connecting rod (Item number - BC67) do you think that suits for my car?

Austin 7 Spares at A7 Components, the Austin Seven Specialists

Thanks
Kiru

Hi Kiru,

I think the parts sold by A7C will be used parts similar to the ones you are looking at (if he has stock). You should ask whether they are crack tested or not. It's hard to judge from photos but the ones you were looking at seem OK to me and price is currently reasonable.

By the way, do you know someone who can re-metal the big end bearings? My recommendation would be John Kirkby in Croydon. Let me know if you would like contact info.

[kirubt]

Hi Chris,

Do you mean i have to get it from A7 C and give it to John kirby for re-metaling

Thanks
Kiru

[Hugh Barnes]

If its relevant, David fom A7Components is away at the moment, not returning until 25th May...

hth...

[kirubt]

Yeah i got out of office message. Does anyone might have these con rods?

Thanks
Kiru

[Chris KC]

Hi Chris,

Do you mean i have to get it from A7 C and give it to John kirby for re-metaling

Thanks
Kiru

Yes, these rods have white metal poured directly into the big end of the rod then machined to fit the shaft, there are no bearing shells.

See Robert's comment above. If you buy second-hand rods (new ones are basically not available), they might already have white bearing metal in good condition, or might not; but they also have to be fitted to diameter of your shaft. 

In case of a new crankshaft the supplier can machine to correct tolerance without seeing your shaft.
But most used shafts have some wear or have been re-ground, then it is necessary to make undersize bearing metal to fit (maybe 0.001" running clearance). 

If you are lucky, your new conrods might already have under-size smaller than your shaft, then you can bore them to fit without re-metalling.

[Hugh Barnes]

I do wonder what the state of the crankshaft is like given the condition of the big end shown. The two components (big ends and big end journals on the crank) need to be in perfect condition. My apologies if this is already understood...