I was wondering has anybody welded the heater hose outlet on the rear iron shut? Also the coolant line from the rear iron that passes through the throttle body to the water pump.

 

Personally I would tap and cap it before welding an iron. You could warp it. Maybe you would, maybe you wouldn't. Do you want to take that risk?

 

the one on the top you can tap for a 1/8npt pipe plug and the side is 1/2npt pipe iirc.

 

That cast iron is not going to weld nicely. Best to pull out the water neck, drill and tap.
Dont use pipe tape, you can end up cracking the casting. Use pipe dope.

 

ok will def try the drill and tap method

 

i just run a hose between the two nipples on mine

 

I've just pinched the end of the thin wall pipe down to a slot and welded them up.

 

What did you use to pinch it?

 

I wouldn't risk cracking the iron trying to tap it, or warping it trying to weld it. Just loop it.

I looped it with a heater core between and mounted it behind the rad.

 

I have done this as well. Also have just hose clamped a rubber cap on there. I just use vice grips to pinch it then TIG it closed. If you could find the right freeze plug that would be a good solution too.

That said I have successfully welded irons in several cases. It can be done if done properly.

 

The one on the top is much larger than 1/8" NPT. 1/4" NPT is the closest once the hole is drilled out very slightly.

1/2" NPT sounds about right for the big heater hose connection, but the casting in that area is VERY thin to use such a large tapered tap.

Actually if using NPT taps on the irons, there is always a significant risk of cracking them. Go very, very, very slow, and use lots of lube (that's what she said!). Turn the tap only about 1/8 to 1/4 at a time, back it out, blow off with air, then go in again for another slight turn. It will take a long time. But you MUST go slow. A friend tried the same trick on his FDs rear iron, didn't go slow enough, and cracked the rear iron upper nipple with the 1/4 NPT tap. The only recourse was to thread in a 1/4" NPT pipe plug, then weld around the area.

I show the tapping of the rear iron in this video:
http://www.youtube.com/watch?v=v-0Yl_Jlx1w

 

Take a couple of 1-2-3 blocks (or any nice, thick, precision ground pieces of anything handy), a large c-clamp, and clamp them tightly across the iron where you're tapping for the plug. It will help immensely in reducing the chance of cracking.

Be very careful when installing the plug. Over tightening the plug can also cause the iron to crack because of the taper. I've also seen this on aluminum trans-axle cases that use NPT instead of a gasket/flange bolt.

 

What about filling it with something like in weld or another epoxy? If cleaned well before won't that work?