oil leaks on early chief engines,1938-45 ???

[oldiron]

Hello,looking for any possible conclusions to why a couple engines are leaking out base studs,base gaskets,cases ,when running on the hwy approx. 60mls an hr. Around town and slower doesn't seem a problem.Have checked breather valve disc ,have oil return to tank that looks normal?? both engines are either new top end,and full rebuild.Even put an extra breather on primary side at timer hole or filler hole.New gaskets where installed and cases sealed. Thanks for any input, Ross

[Bills37]

Hello,looking for any possible conclusions to why a couple engines are leaking out base studs,base gaskets,cases ,when running on the hwy approx. 60mls an hr. Around town and slower doesn't seem a problem.Have checked breather valve disc ,have oil return to tank that looks normal?? both engines are either new top end,and full rebuild.Even put an extra breather on primary side at timer hole or filler hole.New gaskets where installed and cases sealed. Thanks for any input, Ross

Is the problem that it is sumping while sitting and your slinging a lot of oil around before the scavenge pump can clean it out? Pull the drain plug after it has sat for a day or two and see how much oil has collected in the cases.

[tfburke3]

Good advice.Then check again after a ride.Should only be a few oz.
I never ran anything but the stock breather but some swear by Kiwi's crank vent which seems to be a pcv type check valve attached to breather,upside down, without the disc. The mounting above breather hole it allows oil to drain back to case.
Tom

[PRG]

Howdy oldiron,

That would be the top drain plug of the two on later model cases - the lower is literally the drain - the upper the acceptable level for a healthy scavenging/non wet sumping motor.

60mph sustained is a fair clip on a 74CI with typical 3 speed gearing so won’t speculate on ideal breathing arrangement though Indian had what amounted to an in town and roadgoing disc for those riding predominantly in either format. Would caution on crank vents for machines lacking modern intake/exhaust seals. Essentially this/these devices attempt to pull a sustained vacuum in any area actively engaged by lubricant. Indians run very loose valve guide clearances at .004, and that’s when new, thus the motor will attempt to “breath” or draw through the guides, fuel mixture washing off oil in the intake guide and drawing abrasive hot carbon down the exhaust side.