Merc crank clean out plugs
 

Hey guys, so I told the guy I needed a tap and a plug for a 5/8 hole, this is what I got,
Is the correct tap and plug size ?
Thanks ..

Re: Merc crank clean out plugs
 

Not by my standards. 3/8" and 5/8" are 1/4" apart in size. Perhaps someone misunderstand.

Re: Merc crank clean out plugs
 

The nominal OD of a 3/8" pipe is 0.675" and the tap drill size for 3/8" NPT threads is 37/64", so the 3/8" pipe plugs might work for your application.

Re: Merc crank clean out plugs
 

I pretty much get all this, but without going down to the shop, did the 4" crank use some kind of press in plugs originally? Won't these threaded plugs change the balance? I have a recently turned merc crank and it came back witout plugs and IIRC it's up to me to clean out the chips. I think threaded plugs would be more secure. Keep up the discussion on the drill/tap/plug combination and I will assume an allen head type pipe plug. Thanks!

Re: Merc crank clean out plugs
 

Nothing wrong with the proper press in plug. They've lasted for at least 70 years in these engines.

Re: Merc crank clean out plugs
 

yes! you can tap out the holes in the crank 3/8 NPT and screw in the appropriate 3/8 plugs. Obviously, clean out all swarf etc generated by this procedure....

Re: Merc crank clean out plugs
 

When I did my Merc.crank I ordered the plugs from Summit nice alum.plugs.Cliff.

Re: Merc crank clean out plugs
 

I made them from soft aluminum on my lathe.

Re: Merc crank clean out plugs
 

I got brass ones on amazon. Came in a set of 5. I used the 5th one for the hole behind the cam gear. For some reason or other the chinese cast iron ones from the hardware store did not fit but the brass ones went in nicely. One has slightly better tolerances I guess or it is the tap I had. Either way the cast iron ones are a hare bigger.

Re: Merc crank clean out plugs
 

Yes,,,,3/8 pipe thread is the correct size for Merc clean out hole .
Just take your time with the tap,,,,,these cranks are fairly hard .
Tap a little and clean out shavings some,,,,,it’s not too hard,,,just make sure to tap deep enough for the plug to screw in pretty flush .
I like to use Tap Magic for lube,,,it taps better .


Or use stock type cup plugs,,,they work fine as well .

Tommy

Re: Merc crank clean out plugs
 

And I will assume some loctite whichever route I choose?

Re: Merc crank clean out plugs
 

Just for info.... the 'cup-type' plugs that I have, came from Dorman. Available at my local parts store. Seems to me, they look same as original factory plugs. (for me, press in, no loctite. But, I see no reason that loctite would hurt.)

Re: Merc crank clean out plugs
 

Considering that Ford used the drive in plugs for millions of miles with no issues (known to me)
I chose to use the Dorman 555-010 plugs. No Loc-tite, drive in, 3-4 stake marks.
https://www.fordbarn.com/forum/pictu...ictureid=44210