82' f-150 300-6
Today I was replacing the pipe from the manifold to Cat because it had a couple really bad holes. It was really hard to get off, from freeing up the frozen nuts, to removing the stuck end where it enters the the pipe for the catalytic converter. Several hours of cursing and bruised knuckles finally got the pipe removed but also set the stage for disaster.

The new pipe that Canadian tire ordered in for me and they claimed would work, matched up perfectly with the bends of the old pipe and had what appeared to be the right sized flange on the end. They also gave me the "donut" that is supposed to seal the pipe to the manifold.

When I went to install the new pipe, I noticed that the donut had the same profile as the joining end of the manifold. I concluded that that must just be the old donut still stuck inside the manifold. I then proceeded to smack and pry at the end of the manifold with hammers and screwdrivers hoping to free up what I thought was the old donut. After it still didn't budge, I made the big mistake of cutting some slots and even drilling a hole in it!

Just to simplyfy for anyone who is confused: I mistook the piece at the end of the manifold where it joins with the pipe for a donut, and I hacked it up a bit.

After It still didn't move I sat down at the computer here to try and figure it out. After reading a couple posts it appears to me that 300-6's from 1980 on, didn't even use donuts. Did I just wreck my manifold? Is there any way to fix it? I was thinking maybe I could just weld a bead into that hole and around those slots and then just grind it down to shape after. Would that work? What kind of rods would I use?


I checked, and the flange on the end of the old pipe does not extend up far enough to cover the hole (although it does cover the slots mostly). BTW the new pipe does not fit onto the end of the manifold, the flange on it is the same as the old pipe, except the new pipe has about a 1-1/2" length of smaller diameter pipe that extends out past the flange / flare end on the pipe and will not fit into the manifold. I figured that if I can fix the flange on the manifold, I could make this pipe fit by just cutting the 1-1/2" off flush with the inside of the flange / flare.

If anyone can make sense of this post, please help!

 

You can weld cast with "Nirod" It has a high nickel content. 55% is grindable, and 95% is machinable. You have to be very careful. Cast expands quickly and loves to crack. It really should be pre-heated. Just do a very little at a time. You may want to screw a soft steel screw or bolt into the hole you drilled, and then just tack it in place. It depends upon the size of the hole. If you go slow, and have a die grinder, you will be able to do it. I've welded a lot of cast, and one thing I do know. You want to cool it as slowly as is possible. The faster it cools the harder and more brittle it becomes. Herman

 

You can also weld with a 70:18 but you need to peen the weld right away...

 

Lots of pre-heating and post heating, like stated earlier, cool slowly. I have an extra manifold like the one you need. A lot of diferent things were done in the early '80's / and in Canada things are compounded by the slowing of emissions systems introduction. Anyways, if your fix doesn't work I'll sell you the one I have (hot tanked and bead blasted - sitting in storage) for $75 + shipping. It's good to know that there's another truck owner that confirms the obvious difference between the '80's castings and the 70's casting. Good luck - Tetra