318 manifold port?

[KRB64]

Started up the M880 this morning to get a load of wood. When I kicked it down after warming up it sounded like I blew the muffler off. After checking I thought maybe I blew out the manifold gasket but instead I found a hole.

On the right (passengers) manifold, against the fire wall is a perfectly round hole about the size of a 5/8" bolt. I can't feel any threads and have to use a mirror to even see it.

I couldn't have blown a perfectly round hole could I? Is there a port there for something and the plug came out? If so, what size/type threads is it?

[JStinson]

I dunno...

Did it have some sort of sensor in it maybe?

[KRB64]

Must have been. I got the bright idea to look where it had been parked (duh) and found a little flap like thing with a bolt head. Looks like the bolt rusted/broke. Kind of a keyhole cover type deal.

Guess its time for some JB Weld unles I have enough room back there to try and tap the hole to thread in a bolt.

[carter davidson]

Could be the block-off plate for the emission control air injection system not used by the military in it's M880 series trucks. Don't know what thread was used and the bolt would most likely break if I tried to remove it.

[KRB64]

Yep, that would be it. I've just got a 5/8" jammed in there right now.

[DODGEBOYS]

a DIME fits perfect if driven in

[DrPepper]

It isn't threaded....

There should be a hole about 1/4-20 (?) next to it as there is a manifold that goes across the back of the block and has 2 tabs that hold the A.I.R. supply pipe in the back of the exhaust manifolds. Just pulled my 1987 318 engine out a few weeks back and the tube came off before I could remove the exhaust manifolds.

[Gordon Maney]

Small core plug? ....since you say it's not threaded?

[DrPepper]

Here's some pix..........

....of what you probably have.
http://s182.photobucket.com/albums/x...Power%20Wagon/

This is both ends of an '87 318 exhaust manifold. The front is plugged with a threaded plug. Back air inlet is as I said, a copper tube manifold held into the back with two tabs brazed to the tube and screws. Second thought is they were 10MM. The copper tube is connected to the air pump. The manifold is ported (drilled) to discharge air into each exhaust outlet.
Hope this helps.
DrPepper

[KRB64]

Yep, that third picture shows it. The 5/8" bolt I jammed in there is still holding so far. If it blows out I'll try some JB Weld. 76 M880 came with 0 smog so I don't need that port.

[712edf]

In the emissions crazed 70's the idea was to inject fresh air into the exhaust manifold in order to prolong the combustion process (burn up more of the waste gases).

The bolt sholud work for a while, maybe forever. JB weld too, but I have seen it get brittle over time.

You can thank Government regulations for the manifold even having the port. Of course it was used only on civilian trucks, not the gov owned ones. Ironic huh?

Bucky