Pony bearings

did you coat the aluminum with any material or will the aluminum run just fine on the cast crankshaft?

Didnt coat it with anything. Should be fine though, I guess I will find out.

The first bearings were babbit lined shells, then at some early point Cat went to Alum bearings. I don't know what the factory alloy is, but I have used 6061-T6 successfully. I don't want you to think I'm poking fun at you, but when you use a lathe, the item is "turned", not lathed. For some unknown reason, when you use a milling machine, the item is milled, of cource, when something is "bored" it can be done on any machine capable of boring. It that clear as mud? in anycase , hope that wasn't too boring😆

I can see no reason why a suitable grade of aluminum should not work well. Briggs and Stratton have been making lawn mower engines for decades and they just run the aluminum conrod direct on the big end journal with no extra bearing material at all.

Julian.

Anymore alot of car makers are using only an aluminum head and running a cast iron camshaft in them however what they are doing is boring the diameter slightly smaller than the OD of the cam then they will swedge the housing there by compressing the aluminum in the housing and making it more dense. This gives the aluminum a tougher surface to be used, this is also what Briggs and other manufacturers have been doing for years and it helps with the heat transfer and reduces the expansion of the aluminum to heat.
Mike

Anymore alot of car makers are using only an aluminum head and running a cast iron camshaft in them however what they are doing is boring the diameter slightly smaller than the OD of the cam then they will swedge the housing there by compressing the aluminum in the housing and making it more dense. This gives the aluminum a tougher surface to be used, this is also what Briggs and other manufacturers have been doing for years and it helps with the heat transfer and reduces the expansion of the aluminum to heat.
Mike

Mike, that's interesting, I'd never heard of that technique - I always assumed they just line bored the heads.

I read that BMW make con-rods as one piece then hydraulically fracture the big-end to make it a two piece rod and cap.

Julian.

That is how they are doing it. I did some work on an Audi A4 that had galled the front right cam housing. My boss at the time was a real cheap azz. Audi had some tech bulletins out concerning this situation and their advice was to replace the head. My bosses advice was to take a skin cut of the housing and he was going to build up the cam and regrind it. I noticed that the initial cut produced a a hard sharp almost wire like chip. After going thru the first .005 of material I got a rough and ragged wire. We did hone slighty to get a smooth finish but this was all in vain, the housing failed before even 1 hour of run time on the engine. At that point we had the time involved in the machining, r&r of the head and then a replacement head and 1 more r&r. If he had taken the advice of the tech bulletin it would have saved the company some money but also some credibility as he tried to charge the customer for his own ideas.

The connecting rods that you were talking about from BMW is what is called "Cracked rod technology" and Dodge, Ford and GM are now all using this process. They will cast the rod as a unit and then do a rough machining of the big end, drill and thread for the rod bolts and score the insides enough to make a weak point in order to split the 2 pieces and then hone the ID to a standard size. This produces a rough break that will only line up perfectly with that one particular rod. Connecting rods before this came into play had the surfaces both machined flat at the partings and allowed the partings to be machined enough to reduce the ID of the rod and allow it to be honed back to a standard housing size. with cracked rods the only thing that can be done is to hone the rod to a new ID however the replacement bearings for these rods are only available in up to a .002 oversize. We have fallen into "Throw away society" and the old ways of doing things will be lost not too many years from now.

I hope this was informative and gets the mind gears turning as to where we are going.
Mike

Its actually old school technology. Johnson and Evenrude boat motors have used these type of rods for years. I saw it for the first time on an old 1976 75hp johnson motor I rebuilt. Anyhow If I get a chance I will post some photos of my rebuild. I just got done acid dipping the block and parts to take off the last 70 years of 70 coats of paint and oil. Its looking pretty good so far.