mac's and loose bearing side plates

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Jeff Campbell
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Re: mac's and loose bearing side plates

Post by Jeff Campbell » Sun Nov 14, 2010 6:23 pm

I guess it depends how loose a side cover is, I wouldn't use one that was real loose, but I have used many that the bearing would just slip into by hand at room temp, those I mounted with red loctite .. and they seem to have all held fine.

While, I am think about it, I will mention it here... another great product for sealing up your macs... Permatex Moto Seal. To me it seems like modern version of the old non-hardening Permatex Form-A-Gasket No. 1. This product was designed for use in small engines. The moto seal product is much lower viscosity than the old form-a-gasket product, so its really well suited to smearing on both sides of a gasket without adding thickness or getting uneven thicknesses. This stuff really does allow you to disassemble the engine without destroying your gasket. This is the first product that I have ever used that really lets you seal a gasket, disassemble and re-use the gasket. IMO, its worth giving a shot.

Jeff

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Rick Chapman
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Re: mac's and loose bearing side plates

Post by Rick Chapman » Wed Nov 17, 2010 12:09 am

I read all your posts and am surprised that no one mentioned one thing.
If it's cracked, it will probably air leak.
If you fellows have your bearing pockets repaired, you better presure test your engines and make sure that crack is not going to turn into an air leak. You better have a big tube of JB Weld available to stop those leaks.
That has been my experience.
Good Luck..
Rick
I Never Thought I'd Be Vintage !!

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steveohara
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Re: mac's and loose bearing side plates

Post by steveohara » Wed Nov 17, 2010 4:42 pm

Rick,

I've not run across one that has cracked all the way through to the outside. I find the material surrounding the bearing pocket cracked once in a while and I have attempted welding but the alloy is just too crappy to weld... at least on the parts I tried to fix. Sleeving a cracked bearing pocket won't work, the crack just gets bigger. I have repaired one that was cracked by machining the OD of the section around the bearing pocket and the fitted a ring machined to press over the OD that was set up with .004 interference. The clamping effect reduced the ID of the bearing pocket by .0015 which took the pocket diameter from a half thou too big to one thou less than the bearing diameter. It worked great but the approach only works on the real short stroke engines that do not require the flat machined to clear the piston skirt as you see in the motors with 1.635 or longer stroke.
Steve O'Hara
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