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

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.

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.

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

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

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.

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.

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

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.