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 Posted: 11-10-2018 09:17 pm
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Esprit2

 

Joined: 05-01-2005
Location: Minneapolis, Minnesota USA
Posts: 547
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DonBurns wrote:
I don't think rope seals were the distinguishing factor. Only very early Mark I had those. Correct?
All Mk I 907s had rope seals, and the Mk II was introduced in Aug 1973

answerman wrote:
The crankcase ventilation was different on the MkI, at least the early ones, with a separator/catch can in the breather line. MkIIs and later vented directly to the airbox.The Mk I 907's crankcase ventilation did not include a built-in oil separator, so a separate oil separator/ catch can was mounted on the firewall. A bottom drain and hose returned oil to the sump as fast as it was collected. An upper hose vented fumes to the carb airbox.

The decision to add the oil filler neck & cap to the catch tank was probably not the best, since the drain hose was small diameter, and it took 'forever' to refill the sump when changing oil.

The Mk II received a 'lip' style rear main seal, mounted in a bolt-on rear cover/ housing. Inboard of that cover, built into the back end of the cylinder block, is a cavity designed to be an internal oil separator. With that added to the engine, the external separator/ catch can on the firewall was deleted, and an oil filler neck & cap were added to the intake cam cover. Being more oil free, crankcase fumes were vented directly to the carb airbox where they were drawn into the engine and burned.

Regards,
Tim Engel