Vaccum pump Mainseal damage

[Kenny M]

I completed a 351 9.5 deck Aluminum Ford motor sport. I am using the GZ pump and the M-6701-B351 High temp Viton seal. On the Dyno Vacuum went as high as 17" 8000 RPMs 851HP. Ten Dyno runs it ran great, but at idle we could here a very light whistle. We loosened the oil fill cap and the whistle went away. So I was thinking it was something vacuum pump related. Not even a hit of seepage after the Dyno. We just went testing with the Vacuum backed down to 10" After 3 runs, Main seal is leaking very bad. One piece seal with Callies crank. Everything measured perfect. I am removing the seal tomorrow, but it looks like it wore down the seal and made clearance between the seal and crank. I am going to replace it with the Cometic C5391 seal. Is this a common problem??

[Nwguy]

We have always run double lipped seals on our dry sumped motors. Available from Peterson I believe or CV products. Been years since I built one, but those were the sources then.