shuffle pin
 

In Bruce Andersons book, he advises against shuffle pinning the 3.0-3.2 engine cases. He doesn't explain, anyone know why. Bob

Aluminum cases are inherently more stable than the old mag cases. It's not needed.

Yes, much stronger, but Bruces implication seemed to be stronger than, well it doesn't need it. Was thinking that the aluminum expansion is greater than that of the steel pins, and they wind up rattling aroung in there shuffle holes after engine is warmed up. Race engines need all the love you can through at them.

Not needed until 400HP at least. Also pins is not the right way to do them. When needed, we do them with sleeved bushings like on the #1 bearing except on every through bolt.

Agreed. Porsche uses bushings for the #1. One of the issues with shuffle pinning is getting the holes "indicated" - both sides exactly lined up. I hear about CNC etc accuracy for this, but you don't need that for bushings.

To bush, you bolt the case together, bore through throughbolt holes one at a time (which guarantees each side matches exactly), and then machine a cylindrical plug to insert into the case side you bored from (because the drill bit will have enlarged that hole). The throughbolt washer is wide enough that it doesn't bear on the plug, though you could make the plug and hole stepped as well.

Of course, you have to be careful with the bushings to avoid blocking any oiling holes which use the throughbolt passageways.

I've always had this done on my sand cast cases, and on the early 3.0 case for a SS2.8 also. Perhaps unnecessary, but certainly doesn't hurt anything. For sure I'd have it done (and I did) with a mag case.

I disagree that it is a low precision operation. We've extensively measured the porsche bushings and found them to be within .0005 tolerance on the OD. They are actually very precise.

Ideally you have a way of fixturing the case so that all of them can be bushed at the same time, and CNC is really the only way to do it accurately enough to ensure you won't have line bore problems introduced by bushings that are off.

Catorce - I don't recall suggesting the Porsche bushings were low precision. My point is that by boring with the cases joined you can exactly locate the additional bushings for the other journals, and don't need CNC or special fixtures for that. Of course, you do have to be a machinist with the tools and skills - not a home brew guy like me.

I agree that you can do it in that manner, all I was saying is that the danger with shuffle pinning is that you can introduce some serious problems into the fit of your case halves if you do it sloppy.

Your method is the one I would use if I was doing it without the benefit of CNC.

bushings for case.
 

I only add 4 to split the difference in the center.RSR engines add a shoulder in the center to aid in alignment with a flat area on one side for oil flow and it was quite effective,All the race motors after had a varying degree of that.Ciao

Here's ours.


http://forums.pelicanparts.com/uploa...1566435492.JPG

Thanks for everyones input on this. I do like the version of sleeves at the though bolts. Pinned my case conventionally, and it is an enormously tedius operation. I figured accuracy had to be within .001''. .0005 would be preferred, but depends on your equipment.

HI, has anybody used these thru case bolts that act like shuffle pin.

https://www.neilbainbridge.com/Products/Details/45/Porsche-RSR-C-Case-Through-Bolt

They seem like a good idea to get the benefits of shuffle pinning with out having to do machine work.

john

Besides that write up being totally full of crap, he does mention that you still need machining to make it work....

I thought I had read somewhere that these 935 style through bolts had the wider section to damp vibrations or something of the sort, not to be used to pin the case together.

The case through bolts are not perpendicular to the case at the spigots, and thus not to the parting halves, are they? Some Porsche race motors used a special two piece washer - the outer piece was convex on the case side, the inner one concave on the side away from the case. Prevented a bending moment when tightened.