Rocker arm bushing source

[cstreit]

Nice work Craig!

[hcoles]

cgarr,
is Buntings just sourcing from Kolbenschmidt or is this a whole new teflon development by Buntings? I don't know how big Buntings is but the KolS efforts are probably not for shallow pockets. This could be the be all end all for rocker bushings.

[cgarr]

Buntings may be a knock off of the KS and I would guess thats the case at only 90 cents each, the KS list at $4.00 each which is still cheap, cheap, cheap... and that list, thats not what we pay..

[911 tweaks]

amazing info craig! My head is spinning, no pun intended, of all the applications inside an engine this could be used... maybe an engine with minimal oil for maintaining some specific tolerances inside the engine... but basically the oil is the medium to carry away the sm metal pcs to the filtration sys and not using oil in its traditional role(s) of: lubrication; heat mgt; remover of metal particles.
Way cool! I have to read up on this. Do you know if this can be "applied" to existing parts or only for new mfgrd parts?
Bob

[cgarr]

Just talked to the Rep at Motion Ind. and Bunting, Garlock and KS (Permaglide(R) are all the same material, just a big price difference. They have thousands in stock!

You can go into http://www.applied.com and look up the specs on all sorts of bushings. This is the spec for the Garlock bushing:

# Steel backing gives DU its exceptionally high load carrying capacity; thin, compact design; excellent heat dissipation; and dimensional and structural rigidity.
# Porous bronze innerstructure: This comprises a nominal 0.010 inch (0.25 mm) thick layer of carefully sized bearing quality bronze powder which is sintered onto the steel backing. This porous structure is impregnated with a homogeneous mixture of PTFE (polytetrafluoroethylene) and lead. In addition to providing maximum thermal conductivity away from the bearing surface, this unique bronze innerstructure also serves as a reservoir for the PTFE-lead mixture.
# PTFE-lead overlay: This low friction overlay, approximately 0.001 inch (0.025 mm) thick, provides an excellent initial transfer film which effectively coats the mating surface of the bearing assembly, forming an oxide type solid lubricant film. As this film is depleted, the relative motion of the mating surface continues to draw material from the porous bronze layer. When conditions are severe, the feed of lubrication is increased. The peaks of porous bronze coming in contact with the mating surface generate localized heat and, due to the high thermal expansion rate of the PTFE, force additional lubricant to the bearing surface. The relative motion of the mating parts wipes the lubricant over the interface, continuously restoring the low friction surface film.
# Loads - P: dynamic pressures up to 20,000 psi (140 N/mm2) assuring high load carrying capacity and excellent resistance to shock loading
# Speeds - V: Speeds up to 1000 fpm (5m/s) without lubrication; 2000 fpm (10 m/s) with lubrication
# PVs to 50,000 psi-fpm (1.75 N/mm˛ x m/s) for continuous operation, 100,000 psi-fpm (3.50 N/mm˛ x m/s) for short-term use. In actual operation, DU bearings have been successfully used at levels which approach 3,000,000 psi-fpm (105 N/mm˛ x m/s) lubricated.
# Temperatures from -328 °F to 536 °F (-200 °C to 280 °C) making it suitable for use in applications well beyond the scope of most liquid lubricants
# Ideal for all types of rotating, oscillating, sliding motion, and both radial and thrust loading
# Can be used totally dry, fully lubricated, or with intermittent lubrication and can be used in the presence of many industrial liquids

[BoxxerSix]

Originally Posted by cgarr

# PTFE-lead overlay: This low friction overlay, approximately 0.001 inch (0.025 mm) thick, provides an excellent initial transfer film which effectively coats the mating surface of the bearing assembly, forming an oxide type solid lubricant film. As this film is depleted, the relative motion of the mating surface continues to draw material from the porous bronze layer. When conditions are severe, the feed of lubrication is increased. The peaks of porous bronze coming in contact with the mating surface generate localized heat and, due to the high thermal expansion rate of the PTFE, force additional lubricant to the bearing surface. The relative motion of the mating parts wipes the lubricant over the interface, continuously restoring the low friction surface film.

See this is quite interesting. I wondered how the teflon stood up to your MAPP gas/lathe test there as PTFE really starts to deform and rapidly expand under heat but that paragraph really explains the impregnated coating and how they're using the PTFE's thermal expansion rate to a great advantage. It's sort of like a miniature Accusump for the rocker shafts

As far as the coating deformation under the load of the spring tension while installed in the motor, virgin PTFE has a ~20% deformation percentage rate measured at 1500psi at 200F. Being that these have a compound, I'd imagine that deformation rate to be even greater(and coupled with the bushing material itself). I think they're going to hold up great

Pretty neat stuff here.

[hcoles]

can someone make up a few bushings and throw them in a car and see what happens? Can the Permaglide bushing take honing to fit? What is the recommended clearance against the shaft?

[burgermeister]

Awesome! I rebushed my rockers for $35.00... can't beat that.

A drill, dremel, bench vise, a 14 & 17mm socket, and a 3/4" copper coupling were all the 'professional tools' it took to press the bushings in & out. Drilled oil holes after pressing in the bushing, flared the hole slightly with a dremel - took <10 minutes per arm. They didn't even need any honing to fit.

Thanks Craig! If you plan on attending an RSR/PCA Grattan event, send me an email with your beer preference ...

[hcoles]

Excellent, I'm going to mention this to a buddy. We are pulling his 3.2->3.4L engine out soon. No honing to fit, that is great.

[KTL]

Craig's had these running in some engines subject to some fairly good abuse. I'll let him share what engines they're running in.

[brads911sc]

Isnt this part of every rebuild he does for people? If so, probably alot of these in engines since he is the go to guy for Rocker rebuild. he did mine.

[Ken911]

I put these in during my last rebuild. the after market rocker shafts wore pretty badly. I replaced them with genuine porsche rocker shafts and they have been doing fine ever since. I have about 20k on the rebuild. Next year when i pull it apart again for the efi swap I'll post some pictures and an update.

[Lapkritis]

How are these holding up?

[Lapkritis]

Are these killing the rocker shafts once the coating wears?

[KTL]

No signs of problems in any of the engines i've been around. When installed properly (sized to fit rocker arm bore & squared-up) they have proven to work great.

[Lapkritis]

Just ordered from Motion Industries - Keeping Industry in Motion

Item 37124

[burgermeister]

Mine did not hold up well. Toast at 13K miles.

Sorry for the late reply.

I would suggest honing them lightly with a grape hone and cutting an oil channel to help with lubrication, 2 things I did not do.

[Lapkritis]

Tell me about this oil channel. Honing the Teflon surface would cause damage / premature wear I would think.

[burgermeister]

If you look at your rocker shafts, there is a wear spot. It's on the inboard side. So I would cut a shallow channel from the top oil hole along the inboard side, maybe 1/2 of the way to the bottom hole, to help guide oil in that direction. The intakes and exhausts get the channel located in a different spot according to this theory, since a different hole ends up on top. Wether or not oil gets anywhere by gravity with the engine running is of course debatable...

The DU bushings are a pretty exact fit on the rocker shafts. The DU material expands as it gets hot. So I can see the bushing basically sealing and keeping the oil from getting to the wear spot. Very lightly honing with a grape hone will scratch the DU coating and create a bit of more clearance, but should not remove it completely. The scratches should help it move oil. My rocker shafts had very visible metal transfer from the DU bushing, indicating a lack of lubrication. This is, again, just a theory, and could be complete balderdash.

My engine has other unexplained issues with insane valve guide wear (a local shop is totally baffled as well, so it's not just that I am a clueless moron with left handed retarded monkey disease), so there may be other issues with my engine. One theory is that I, my engine, my car, or all of the above, are cursed ..

Others have gotten these bushings to work, so it must be possible.

[Lapkritis]

If the issue is thermal expansion effectively sealing the bearing surface from oil then a trim where the bearing roll closes would allow expansion to prevent binding. I'm not an engineer though so I don't have expansion rates for the two materials handy to compare. The other alternative if they're too tight would be to open the bore within the rocker.



-Andrew