Intermediate shaft questions

[Walt Fricke]

Max - axial play on all except the early cases/IS shafts is taken up by the double thrust bearing and the shoulders on the IS shaft which are on either side of the thrust bearing. Was that your question?

Gestalt - the axial thrust for the early sand cast case IS shafts which is to the rear is taken up by the cast iron external cover plate. Because end play is adjusted on these shafts by varying the thickness of the gasket between plate and case. This is a well lubricated area, because you don't see wear marks on the cover plate - at least not worrisome ones.

For some reason I am drawing a blank as to what resists thrust pointed toward the flywheel on these cases, but it has to be a flange or equivalent bearing on the case itself at the rearmost bearing web. Which is also well lubricated, as this is where the pressurized oil lubes the bearing area, and also enters the IS itself in order to lubricate the front bearing area.

[AlfonsoR]

Originally Posted by brads911sc

WPC is in CA. I shipped them to CA. Had them back in a week. Total for all Main, Rod and Intermediate bearings was $140 Incl shipping. Cheap insurance.

The Poly Dyn is also very well regarded. I chose WPC because I didnt want to mess with clearances. Its a micro shot peen with tin and other anti wear material.. Poly Dyn is similar materials but is a coating. Both are probably equally good.

In Houston, Id use either M Callas in Sealy (Who I used) or M Crawley at European Auto Technics. Both have old shops filled with old Porsches and have on site machine shops. Both are spendy. My machine work was $800 and its an SC case that didnt need anything. that included having him install the rings and cut them (where needed) (extra $175). Was worth it to me to have that perfect. As a side note.. He didnt install my new wrist pin bushings. Said mine were fine and advised me to use the old ones. So he def isnt trying to sell u extra unneeded work. He marked my pistons based on where he would install them. Very stand up guy...

At either shop Id plan on dropping them off and leaving them for a week...

Thanks for the info Brad. If I split the case, I will go for "perfect" too. I might even upgrade to Pauter or R&R rods, if budget allows.

What brand of bearings and rings did you use?

[brads911sc]

Bearings were all Glyco.

Rings were JE Pro Seal. I also have the 9:5.1 JE Pistons.

Originally Posted by AlfonsoR

Thanks for the info Brad. If I split the case, I will go for "perfect" too. I might even upgrade to Pauter or R&R rods, if budget allows.

What brand of bearings and rings did you use?

[AlfonsoR]

Thanks Aaron, Max, Burgmiester and Walt for the information.

It looks like it's as Aaron suggested, that as soon as you start your freshly rebuilt engine, the IS thrust bearings will begin to wear and will show copper shortly thereafter.

I still have not heard personal experience on straight cut gear and whether that improves IS radial or thrust bearing wear. I hope someone can chime in on this.

[lindy 911]

Since the stock IS gear set up will produce a thrust load by design, it only makes sense that the straight cut gears will not. I would wonder why Porsche used the stock set up in place of straight cut gears as the latter is easier to manufacture. I suspect noise and added surface area of the teeth have a lot to do with it. I would also suspect controlling the back lash of the two gears is easier with the helical cut.

Unless you plan to build a race motor, non-stock rods are not necessary. The money for Pauter rods would easily pay for a perfect bottom end rebuild including re-sized Porsche rods with ARP bolts.

My motor came out at 97,000 miles. Stock '78 SC with some hard miles. The thrust sides of the front IS bearing were in good shape, not perfect but it could have lived happily for many more miles. The second bearing near the pump shaft joint is where the wear showed the most. This is not a thrust bearing simply a plain bearing supporting the pump shaft end of the IS.

[AlfonsoR]

Thanks for the comments Lindy. I found Michael Knights info on the web. Once I figure out what I want to do, I will contact him.

I only mentioned the upgraded rods because I was thinking of future proofing the engine, as in, I have an eye on possibly (key word there) upgrading to a Protomotive type set-up somewhere in the future.

Any way, the top-end has been done. And if I upgraded the bottom end, "all" I would have to do is look at cams, turbo, and exhaust. A sort of piece-meal way of upgrading to 350 hp or so.