Intake Manifold Vacuum Plug

Anyone know the specs or the name of the plug that goes into the vacuum port of a Dauntless intake manifold? It is replacing the plugged line that presumable went to the wipers. FLAPS said it looked closest to a 10 mm ultra fine thread, but that seems like an odd choice for a 56 year old American car.
Thanks.

 

I bet it's 1/8 NPT
Sounds like your parts counterman doesn't know what he's talking about.

 

It is 1/8" NPTF.

 

I usually take a plug tap and clean out the threads before putting plugs or fittings in existing spots.

 

I don't recommend that for an Intake Manifold where the ports are not easily reachable with a magnet to catch shavings.

 

Yep. Unless you can stuff a rag or something else under that port to catch ALL the debris, that is a no-no. All that debris will get sucked directly into the cylinders. Same scenario on any port in the oiling system. The only time to chase those threads is when you have a bare block/head/manifold can be thoroughly cleaned.

 

Keep in mind that NPT (National Pipe Tapered thread) is in fact a tapered thread. By running a tap in, you may actually enlarge the threads, making fittings fit deeper or possibly bottom out if there is a shoulder. This type thread is typically used for fluids, but also vacuum as found on an intake manifolds. These threads can be sealed with thread tape if you use the correct color tape for the application.
-Donny

 

Great tips. Thanks.

 

shop vac on the intake. And I'm not saying ram the tap through there so that you're cutting the threads deeper, just to knock off the loose crud.

and for oil ports, I put assembly grease on the tap, all the crud sticks to the grease. I've never had problems doing this, but it's good to be aware of where the crud will go.

 

Ayuh,.... On my dauntlas, there's 3, 1/8" pipe plugs across the back runner, 1 is plumbed to the GM T350 transmission, 'n 2 were plugs,....
Just last week, I pulled the center plug, 'n installed a vacuum gauge,.....

 

1/8 NPT was the winner. My plug should at least look better then the tubing with a sheet metal screw in the end!

 

Maybe but if the intake is closed on that port, you still are not going to get much vacuuming action. I prefer to error on the caution side.

 

or you could just put a plug in there and hope no crud falls through