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!

 

I just changed out the manifold on my 80/I6 & had a similar problem. The manifold I picked up was off an 86 or so & it sounds just like yours, the one I needed looked the same without the "molded donut". I took it back & replaced it with one that came off an 80. It was $20 at a you pick & I had it changed in a couple of hours, including driving time. It might be simpler for you to go this way as you will probably have to pull it to weld & grind.

Chris

 

They make those manifolds out of some nasty cast metal. I tried nickel rod on one one time and it popped and fizzled and would not weld at all. Junk yard would be the ticket.

 

okay, sounds like I'm replacing it then. It is my understanding from what I have read, that you can't just unbolt your exhaust manifold off the block and then bolt on a different one. I've read things about machining the replacement manifold and even the block. I also read about hot tanking - explain what this is please.

how much will this cost? should I do the intake manifold at the same time, even though it's working fine right now? Do I need a gasket? What sorts of things should I watch out for in a used replacement manifold that I'll be picking up from the junkyard?

I'm using this truck as a work truck for hauling lumber and stuff around. i'm really not looking to give the truck any major performance upgrades and as I'm only 17 I'm kinda strapped for cash.

thanks for your time,
Alan

 

I don't see why you can't bolt another one on. The factory usually never used an exhaust manifold gasket(on the v8's anyway), and if it is warped or pitted a little you can use gaskets to take up the slack.

 

Really? I feel a bit better then. I guess this won't be as costly as I thought. Any other tips about torquing or anything? I've never installed these before.

Thanks,
Alan

 

Yea, unless you have already modified it, I would take the pipe back and get the right one. I don't know if you are into experimenting or not, but I thought this was a neat idea, and somebody mentioned it here once too, about how the later fuel injected sixes have dual manifold outlets. I have always heard that a six with dual pipes really sounds neat and have always wanted to try it. You would have to do some head scratching though to see if it would fit.

 

[font size="1" color="#FF0000"]LAST EDITED ON 05-Nov-01 AT 09:10 PM (EST)[/font][p]I know someone who had duals on his 6, it sounded almost like a V8. Only if you know what to listen for can you tell the difference. It is just a little quieter, too, if I remember correctly.


88 F-150 4X4 XLT Lariat w/5.0 EFI 5 spd (DAILY DRIVER)
86 Ranger 2WD w/2.3L EFI 5 spd to be 351W 4bbl C4 (NEW TOY- DETAILS WHEN FINISHED)
85 Old Cutlass Supreme 350/TH350 Holley 4160,Edelbrock Performer intake, el-cheapo headers, General Kinetics 270H series cam, 15.588 best 1/4 mile with original 10 bolt 2.41 gears (OLD TOY)

 

Yeppers you messed up!
you will have to preheat the metal in order to make it accept a brass rod to braze it so it won't fall off as you attempt repairs.. or......
there is a special rod on the open market that you can use to weld on cast with {I use Chronatron at work}I am sure there are several other companys that make this type of rod , but I have had some limited luck using this method with this product but be advised I have also had several failures after a period of time also so you go with do I attempt repairs or just change the part.
if you go this way then make it superclean before you attempt repairs using eathier method
I did attempt the brass rod on a ehaust manifold on a chev tk and after much wasted material and excessive swearing, I was looking at it and realized that the casting had the same # on it as my Nova of which I had 3 cars there to build 1, so I got lucky there as I just had to grab a part and bolt it on,{several hrs later},you may want to run a cross ref and see what else you may get away with, maybe you can get a used part cheaper then to attempt repairs as cast is a different animal to repair, it can be done but there is a price tag attached
good luck bro let me know how you make out
Cutter ö¿ö