Rocker bushings question........

[boyt911sc]

I am having the rockers for a 3.0 liter SC engine bushings replaced. The machine shop doing the work has no bushings and they wanted me to provide them. The bushings from PP came in today.



To my surprise, the new replacement bushings are not seamless like the OEM bushings. I have a set done before some years ago and the bronze bushings were seamless (no cut). See picture above. Anyone used these new bushings lately? Any advise? Thanks.

Tony

[Tippy]

They'll be reamed to size, and that split may act like a nice channel to hold oil. Meaning I wouldn't see it as a bad thing.

[JJ 911SC]

Originally Posted by Tippy

... and that split may act like a nice channel to hold oil...

You got it. Also known as Self Lubricating PLAIN SLEEVE BEARINGS | Split Type - Inch

[boyt911sc]

I was expecting to recieve the seamless bushings and never have used this type of bushings before. So these are better bushings that the seamless ones? Anyone have used them lately? Thanks.

Tony

[cgarr]

They don't make a seamless in a steel shell bushing, they are too thin, have them install with the seam to the top of the rocker arm and chamfer the oil hole.

[JJ 911SC]

Both illustrations, the Porsche version (901-105-341-01-OEM) or the Glyco (901-105-341-01-M41) shows that slit.

I would be pretty confident using them but there is nothing like getting a confirmation from someone having use them especially if its from ccgarr...

Pelican Parts - European Automotive Parts and Accessories - Porsche • BMW • Mercedes • Volkswagen • Audi • Saab • Volvo • MINI

[boyt911sc]

Originally Posted by cgarr

They don't make a seamless in a steel shell bushing, they are too thin, have them install with the seam to the top of the rocker arm and chamfer the oil hole.

Craig,

How is your work schedule? Could you still accept this job order and provide bronze bushings? PM sent. Thanks.

Tony

[Walt Fricke]

Craig now has several years on his Oillite type bronze bushings. I haven't seen anyone find a fault with them. I wonder if they have been around long enough that their longevity can usefully be compared to the standard split bushings?

[chris_seven]

These are the standard bushes - they aren't just made like this for Porsche. They have always been a split steel backed bush and they have always had the split line. If you examine the original rocker carefully you will find the split in every case.

They are a Glyco semi-finished bush and have always been reamed/honed to size after installation. 56-2698 SEMI is the Glyco Part Number.

We have used hundreds of them in the forged rockers we manufacture and Porsche first used them in 1965-67 and them from 1969-1989 and then for the 964.




Every 911 engine ever made has used this design of bush with the exception of the first generation cast steel rockers used between 1967 and 1969 which didn't have bushes and used to gall the shafts quite badly.

The 906/RSR Rocker doesn't have bushes by make use of a hardened steel rocker shaft made by Porsche Motorsport. We make a replica of this shaft to complement our forged rockers.

The position of the split line is not too much of an issue providing it is not in line with the oil holes and making the 'tear drop' chamfer is not really an issue but I would agree that any burr needs to be removed.

Oilite is not really suitable for this application - it is not the ideal material and it is not something I would consider.

The sliding speed of the rocker on the rocker shaft is around 5 Times the recommended maximum speed rating of Oilite and its pressure rating in thin section is also inferior to the steel backed bearing.

I always believed the Craig used a KS manufactured Permaglide Bush as an alternative to the Glyco, and not Oilite but I could be mistaken.

There have also been rockers re-conditioned with GBB - DU bushes which are also similar to Permaglide. These bushes are also steel backed and are split. They are a combination of PTFE and sintered bronze, they need holes machining and I think that are generally unsuitable for in situ honing.

Due to this fact I have concerns about obtaining the correct clearances with either Permaglide or DU but both are likely to perform better than Oilite.

A con rod bearing material such as AMPCO 18 would work and could also be in situ honed but is more expensive than the Glyco part.

These Glyco Bushes are ideal for the application and work well.

Purchased directly from Glyco or even from Rock Auto they have a cost of around $3.00 each.

We always precision hone them to size rather than ream and the size is provided in the 'Spec Book'.

We use the Glyco bush because we consider it to be the optimum solution so why not just use them? The split line is just not an issue.

[boyt911sc]

Chris,

This is the kind of post you contribute to this forum. A well explained and detailed facts that make coming to a decision easy. Packing the set of rockers to be shipped and machined in Michigan. Thanks.

Tony