Zero Drag Seals

[Tom Foley]

Are these seals hype or can an increase in RPM be realized ? I have engines with both but have never really done a comparison . Info anyone ?

 

[Danny King]

hype.

 

[Dennis Somers]

Tom, they rely on a thou or two crank clearance in order to be "zero" drag. And because they are held by the rubber seal, they add no support to the flexing crank, and with slight contact over time, they wear even more clearance away. Compared to brand new stock seals, they are less drag. But as new seals get broken in, there is practically no difference in performance. You can have very good performance and sealing, by simply removing the tension springs from the inside of the stock seals.

Zero drags were first offered by Matthew @ M&D Designs Racing. But they were a full metal assembly that took the place of the rubber seals. So they DID add crank support and the clearances were very precise. Others saw the chance to simulate the effect on a cheaper insert.

 

[Tom Foley]

Thanks Dennis for your explanatory response , that was kind of what I was thinking regarding the sealing effectiveness . I'm sure they wear out relatively quick compared to a stock seal .

 

[Jim Allen]

Tom,

There is a method of replacing crankshaft seals that will show a great improvement in engine performance. The seals themselves are actually steel backed PTFE coated bronze sleeve bearings available from McMaster-Carr. Since these sleeve bearings are pressed into their stainless steel housings, they are easily replaced when worn. It should be noted that a crankcase & a crankshaft that is not true would not work in this application! Notice the precision ground (.47210") hardened steel shaft that passes through all four bearings of the precision bored Quick Draw crankcase bottom half without any binding. A "trued crankshaft", which is the full diameter on both ends, will also pass this test. After the entire crankcase bottom half with the precision shaft passing through all four bearings has been zeroed, the aluminum front & back flanges that will hold the stainless steel housings are bored to size. The flanges are accurately relocated with the countersunk flange mounting bolts. The stainless steel housings are pressed into the aluminum front & back flanges. The listed catalogue size will cause the sleeve bearings to completely close. The sleeve bearings are held in its stainless steel housing with a .0005" press fit. The press fiit amount allows the sleeve bearing to have a .0001" to .0002" radial clearance on the crankshaft. I have used these type crankcase seals for several seasons without any wear & the advantage of having the crankcase bottom end effectively sealed at all throttle settings!

Jim Allen

 

[Tom Foley]

Great stuff as usual !