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Posted by: MrHyde Mar 19 2012, 01:52 PM

I just dropped my engine case off at the machine shop to get the cylinder registers decked and oil galley plugs pulled and tapped. I Already have the 3/8"npt steel plugs and was asked by the machine shop if there was a special reason for using steel ones over aluminum. He brought up having the two metals expand/contract at same temps., etc. and I had no other response than " that seems to be what everyone uses"... Soooo.. I don't really want to seem like much of a fool, but why is it that we use steel npt galley plugs vs. aluminum ones ????

Thanks a bunch,
Mike

Posted by: aircooledtechguy Mar 19 2012, 02:03 PM

Use the steel ones. The aluminum ones can gall going in and you'll have to drill it out next time.

I also use a good thread sealer like the white Permatex liquid thread sealer; good stuff and I've never had a leak with it.

Posted by: gothspeed Mar 19 2012, 08:00 PM

I think mine were anodized aluminum. anodizing hardens the surface slightly and if used with sealant they should screw in just fine. I agree with the CTE argument.

Posted by: Valy Mar 20 2012, 01:23 AM

How about brass?
It's hard enough and expands/contracts similar to the aluminum.
Just my 2 cents.

Posted by: MrHyde Mar 20 2012, 10:52 AM

Gonna stick with the steel ones... The engine will be far from stock, so I'll beef up what I can.. Thanks all

Posted by: gothspeed Mar 20 2012, 04:01 PM

I believe the factory interference fit plugs are steel and sometimes fall out and leak ....... but they are not threaded either .......... so you should be fine.

Posted by: Jake Raby Mar 20 2012, 04:29 PM

No, they are aluminum and have very little interference fit.

We ONLY use steel plugs, 16 years later they can be removed with no issue and the galleys cleaned at rebuild.Just a little dab of Milk Of Magnesia on each plug is a good way to ensure they'll never seize.

I have had horrible experiences with threaded aluminum plugs that we have removed from "core engines" that had them retrofitted.

Posted by: MrHyde Mar 20 2012, 04:46 PM

I'm going to try to minimize my exposure to the "horrible experiences"..
I'll stick with the steel ones.. I have them already anyways...

Thanks for the Milk of Magnesia tip. !

Cheers

Posted by: gothspeed Mar 20 2012, 09:59 PM

I checked on my new 2056 engine build and the plugs are steel and have yet to leak. so the alloy ones I envisioned at my friends shop, must have been for something else.