Any way to get a new connecting rod for an old 10cc Grayhead Webra? If new isn't available anywhere, could a regular machine shop bush the rod for you? Or would they just laugh at you, or charge you some horrendus price if they were able to do it? I know it's a lot of work, but it's kind of an old family heirloom... Thanks in advance! Ross

Call Paul at this ph# "http://www.paulsmodelsupply.com/", he is very knowledgeable where Webras are concerned, he fixed me up with that exact rod.

Hobbsy, thanks for your help. Ill give Paul a call and see if I can save this old relic. Ross

Ross,


I am not sure about the con-rod for your Webra, but the bronze bushings could be either cast around (the rod is a casting, with the brass bushes pre-inserted into the mold), or the rod could be forged, or machined from bar-stock, with the bushes pressed in afterward.

I had an HB.40PDP engine that had what appeared to be a cast con-rod.

I don't know what your Webra Blackhead (?) originally had, but if you measure the center-to-center distance between the holes and their diameter (it is in millimeters, not in inches), I am sure there are curent engines that use a con-rod that would be perfect substitution for yours.

NOTE: If the wrist-pin, or the crank-pin is at all worn, or scratched, the replacement of the con-rod would be a total waste of time...

You have to be careful how you measure a worn rod to get the correct centre to centre distance because of the way they wear. The small end wears downwards and the big end wears upwards so you have oval holes top and bottom. The only way is to measure the distance from the top of the small end to the bottom of the big end (the unworn sections) then subtract half the diameters of both the wristpin and crankpin (and maybe another 1 or 2 thou if you want to get anal about it ).

The rod in my Rossi 45 had worn .012" on the (unbushed!) small end which had the same affect as raising the liner by .012" (altering the timing) and also lowering the compression. Making and fitting a bush was fun but very time consuming.

This is true, Brian.

There is a trick which still allows you to take reasonably accurate measurements.

If the hole is elongated, it will likely be only worn at either end of the hole, most likely the compression side (the bottom of the top hole (known as the small end) and the top of the bottom hole (big end).

The holes rarely wear at all at the sides. This could be measured with a micrometer, but the widest place remains in the same place.
The crank-pin and the wrist-pin have a slightly smaller diameters than the holes, to allow some oil clearance, so the wear radius is always smaller than the bore of the holes.

Since this dimension is unchanged, one could measure between the widest part of the top hole and the widest part of the bottom hole, to read the center-to-center distance very accurately.

I removed the rod to call on a replacement. The crank end is plain (no insert or bushing) and the piston end has a larger end with a
needle bearing insert. Seems odd to go that beefy up top and not bush the bottom. Crank and wrist pin look good. Have a new ring
from Frank Bowman and don't want to run it until a new rod goes in... Pauls wife says he's gone today and will contact me ASAP. Ross

Ross,


The needle bearing top end suggests Webra thought lubrication would be marginal in this location.

I don't think there will be a replacement from another manufacturer, so I hope Paul will manage to find a new original part for you.

Time is money , but if the crank rod has enough meat it could be reamed out and a new bushing pressed in. Doesn't Clarence Lee do this kind of machine work. This takes fine small tooling which your average machine shop wonn't have. You need to send crank with rod to get a good fit. worth the trouble since it is an heirloom?

You might try ( http://www.webra-austria.at/) They may reply or not?