The Ford Barn

elwood · 11-08-2021, 09:24 PM

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 ..

tomcarman · 11-08-2021, 09:52 PM

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

Zeke3 · 11-08-2021, 10:04 PM

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.

GB SISSON · 11-08-2021, 10:23 PM

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!

flatjack9 · 11-08-2021, 11:17 PM

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

Brian · 11-08-2021, 11:52 PM

Sponsored Links (Register now to hide all advertisements)

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....

transbytip · 11-09-2021, 12:54 AM

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

vincent · 11-09-2021, 01:46 AM

I made them from soft aluminum on my lathe.

Frank Miller · 11-09-2021, 08:06 AM

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.

Desoto291Hemi · 11-09-2021, 03:22 PM

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

GB SISSON · 11-09-2021, 03:53 PM

And I will assume some loctite whichever route I choose?

bobH · 11-09-2021, 04:31 PM

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.)

51 MERC-CT · 11-09-2021, 04:45 PM

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.

11-08-2021, 09:52 PM	#2
tomcarman Senior Member Join Date: Feb 2017 Location: Rochester Wa Posts: 574	Re: Merc crank clean out plugs Not by my standards. 3/8" and 5/8" are 1/4" apart in size. Perhaps someone misunderstand.

11-08-2021, 10:04 PM	#3
Zeke3 Senior Member Join Date: Dec 2014 Location: Columbus, IN Posts: 1,592	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.

11-08-2021, 10:23 PM	#4
GB SISSON Senior Member Join Date: Jan 2014 Location: Orcas Island Washington Posts: 5,881	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! __________________ Owner/Operator of 'Jailbar Ranch' on the side of Mt. Pickett. Current stable consists of 1946 1/2 ton pickup turned woodie wagon with FH V8, 1946 Tonner Pickup with 226 H six, 1979 Toyota landcruiser wagon, now wearing 1947 Ford Jailbar sheet metal. 'Rusty ol' floorboards, hot on their feet' (Alan Jackson)

11-08-2021, 11:17 PM	#5
flatjack9 Senior Member Join Date: May 2010 Location: Oshkosh, Wi Posts: 4,600	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.

11-08-2021, 11:52 PM	#6
Brian Senior Member Join Date: May 2010 Location: Masterton, New Zealand Posts: 3,998	Re: Merc crank clean out plugs Sponsored Links (Register now to hide all advertisements) 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.... __________________ Unfortunately, two half wits don't make a whole wit!

11-09-2021, 12:54 AM	#7
transbytip Senior Member Join Date: Dec 2011 Location: ottumwa Ia. Posts: 132	Re: Merc crank clean out plugs When I did my Merc.crank I ordered the plugs from Summit nice alum.plugs.Cliff.

11-09-2021, 01:46 AM	#8
vincent Senior Member Join Date: Jun 2020 Location: Germany Posts: 243	Re: Merc crank clean out plugs I made them from soft aluminum on my lathe.

11-09-2021, 08:06 AM	#9
Frank Miller Senior Member Join Date: May 2010 Location: Auburn, MA Posts: 2,106	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. __________________ “The technique of infamy is to start two lies at once and get people arguing heatedly over which is true.” ~ Ezra Pound

11-09-2021, 03:22 PM	#10
Desoto291Hemi Senior Member Join Date: Oct 2019 Location: Carthage , Tennessee Posts: 199	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

11-09-2021, 03:53 PM	#11
GB SISSON Senior Member Join Date: Jan 2014 Location: Orcas Island Washington Posts: 5,881	Re: Merc crank clean out plugs And I will assume some loctite whichever route I choose? __________________ Owner/Operator of 'Jailbar Ranch' on the side of Mt. Pickett. Current stable consists of 1946 1/2 ton pickup turned woodie wagon with FH V8, 1946 Tonner Pickup with 226 H six, 1979 Toyota landcruiser wagon, now wearing 1947 Ford Jailbar sheet metal. 'Rusty ol' floorboards, hot on their feet' (Alan Jackson)

11-09-2021, 04:31 PM	#12
bobH Senior Member Join Date: May 2010 Location: so cal, placerville, vegas Posts: 1,414	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.)

11-09-2021, 04:45 PM	#13
51 MERC-CT Senior Member Join Date: May 2010 Location: East Hartford, Ct Posts: 5,898	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. __________________ DON'T RECALL DOING SOMETHING FOR MYSELF BASED ON SOMEONE ELSE'S LIKES OR DISLIKES