I removed the emissions air pump from the motor and now I need to plug the whole where the tube from the pump goes into the manifold. the size of the fitting that attached to tube appears to by 7/8" x 18. I have looked in several catalogs, including Pegasus, but I have not been able to find any plugs that size. Anybody have any other sources?

Thanks.
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7/8 - 18 is kind of an odd size. It's somtimes used in trans. plugs and truck oil drain plugs. Pegasus has one listed but it has a magnet. See link below. Locally you can check a Detroit Diesel dealer. I think the Series 40 motors use this size as an oil drain. Both of these options will have an external hex head and flange which you may not have room for in your application.
If you don't have the space for the flange and need a socket type plug try a local hydraulic shop.

-Bob

http://www.pegasusautoracing.com/pro...s.asp?RecID=20