Cam bearing material
Cam bearing material
(OP)
I'm in the early stages of design/fabrication of a DOHC conversion to a hemi head (previously pushrod). Each cam will ride in five machined-from-billet "pillow blocks". Is there any reason not to use the "native" aluminum alloy of these blocks (probably 7075-T6) as the bearing surface for the steel camshaft journals (all full-pressure-lubed)?





RE: Cam bearing material
Of course some do use bearing shells. I know VW uses bearing shells to run the cam in the aluminium crankcase on old air cooled Beetles.
The one benefit of removable bearing shells is the repair-ability.
Regards
Pat
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RE: Cam bearing material
"Schiefgehen will, was schiefgehen kann" - das Murphygesetz
RE: Cam bearing material
Well, sure it can be done, but finding the original intended centerline of a worn hole can be time-consuming and therefore expensive.
Mike Halloran
Pembroke Pines, FL, USA
RE: Cam bearing material
"Schiefgehen will, was schiefgehen kann" - das Murphygesetz
RE: Cam bearing material
Also, when doing the original design, the cam would need to be made with journal sizes to match inserts being kept in mind, but either way can work, as can cutting the caps at the parting line to close them down then reboring in parent metal, but that drops the cam into the head, albeit only a few thou most likely.
Also when designing the head, there needs to be enough metal around the cam bores and sufficient spacing of the cap bolts to allow for repairs or inserts.
Regards
Pat
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RE: Cam bearing material
The Jaguar DOHC XK engine used an aluminium head but also used separate replaceable cam bearing shells. I don't know of any other aluminium-headed OHC engine that doesn't run the cam directly in the head material.
RE: Cam bearing material
It depends on the model. Some where Magnesium alloy and some where aluminium alloy. I'm not a metalurgist, so if it is aluminium/magnesium alloy, I don't know at what levels, which one gets the naming credit. I guess whichever is in the largest portion.
Regards
Pat
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RE: Cam bearing material
RE: Cam bearing material
I believe everything wears in there too including the shells, so its a good job they went with them in the end it seems!!
http://dieselrepairblog.wordpress.com/2011/06/09/v...
Brian,
RE: Cam bearing material
RE: Cam bearing material
Unit injectors have been used widely in heavy duty class 8 truck engines by many manufactures but these ~16 liter 6 cylinder engines have a bit more room to fit properly sized cam lobes.
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RE: Cam bearing material
Dgallup, you are correct, I think it was 2009,
Brian,
RE: Cam bearing material
RE: Cam bearing material
Also, may be of interest, found a great company before Christmas should you want to cast the carriers down the line instead of machining(If you're doing lots and the swarf is following you home)
Email drawings, you have parts on your desk 10 days later! No way connected with them, but from someone that often casts runs/prototypes they are a godsend at times for stuff that has a ton of cores, or is a nightmare to pattern.
http://www.prototypes.it/QuickSandCastin-EN.html
Brian,
RE: Cam bearing material
Gotta think piston aluminums are chosen for reasons largely other than bearing qualities, and (hard, highly finished) wrist survive just fine.
Generically aluminum alloys used as bearings lack the various babbits' embeddability and conformability and are even doped with lead, probably for the same solid lubrication reasons bearing bronzes sometimes are.
http://machinedesign.com/article/aluminum-alloy-be...
http://www.kingbearings.com/files/Engine_Bearing_M...