What kind of plugs for exhaust manifolds?

[WarBeard]

What kind of plugs am I supposed to use to plug the holes in my exhaust manifold after removing the A.I.R system? Anybody got any part numbers?

Brass, Steel ETC what is better to go into The cast iron manifold?

[70inline6]

Take one of the A.I.R tubes with you to Lowe's or another hardware store and look at the brass plugs. Match up the size on one of the quick reference cards they have hanging there. Pretty straight forward.

[brakenit]

I special ordered some stainless plugs. The one's on my 250 were M18x1.5, the same size as most oxygen sensors, which is what the plugs I bought were supposed to be for.

[raceman6135]

The A.I.R. tubes are a straight thread because the tube's sealing is accomplished via the 45-degree mating surfaces of the tube to the "cone" inside of the exhaust manifold.

If you can find a straight thread plug, go for it, but when I had trouble finding one, I just used a brass NPT (national pipe taper) plug. The brass is soft enough that as you tighten it, it will deform to the threads in the exhaust manifold and will seal without the need of any threadlocker, or paste, etc.

Since I knew I'd never be removing the plugs once installed, it didn't bother me that I forced the NPT plug into the straight thread manifold.

[WarBeard]

Sounds good! Heading to the store now. As Of last nite I was just gonna weld the nuts from the A.I.R tubes shut, but I just found out my tank for my welder is empty and my welding shop is closed today (Sunday)..

[broey]

they had the plugs I needed at ace. but not enough. so I got the rest at lowes.

[WarBeard]

Were they 1/4-18 thread? I cannot believe they are metric on a '74.

[broey]

i dunno, I just brought the old emission tube I took out with me and matched it up.

[WarBeard]

Here is the part number I used. I stuck the plugs in the freezer and ran the truck around the block (That was loud) so the manifolds were hot making the holes a little bigger and the plugs smaller so it was easier to install.

[cxune]

I'm trying to figure this out as well- I thought I could swap the plugs out of my '78 car 250 into my '83 truck 250- but the '78 holes are much smaller. 3/4 NPT plugs seem just a little too large. Maybe the metric size mentioned will work?

[Corts60]

I've used oil pan plugs for dodge cummins. Works perfect.

[midnight rambler]

How hard was it to get the old tubes out. Did you have tp soak them?

[cleansquare]

Soak them, and use vise grips. Youll need them. They should come out easy. I used 1/4" stainless plugs for my 305 manifolds in the blue truck.

[cleansquare]

[bigd65]

I ha the ONE BIG HOLE in each manifold (87)..... Can't find the plugs to fit those either.... I just welded a bolt onto the end. I would still like to find the plugs to clean it up better

[franken]

If not saving the tubes I'd give them some lube, lop off the tube and put a 6 point socket on them.
Probably just trivia, but I'd wonder about the expansion properties of the manifold vs the plugs. I seem to recall some where the tubes were pressed in and they rusted away. In that case you can torch weld cast iron w/ the right filler.

[83GMCK2500]

I had the 4 individual tubes in my manifolds...they were a king-sized PITA to remove. I ended up cutting them off, forcing a 6-pt socket onto the ferules, unscrewing a few, breaking off the rest. Had to drill out and tap a few, pulled the manifolds to do it. In doing so I realized that this was an opportune time to tap all of the holes just a tad oversize and all my plugs tightened down flush when I was done, easy peasy.