I’ve cleared a couple of exhaust hurdles recently and thought I’d share my experiences. My recently purchased 1970 F250 Camper Special had been modified by the original owner to dual exhaust (glass packs) exiting out the passenger side in front of the rear tire. In my younger years I would have been all about that but in the last few years I have actually become a bit of a purist. I want a bone stock truck. Along with the glass packs the truck had some major exhaust leaks. The right side manifold was leaking like mad as well as the right side doughnut.
I stopped at a little hole in the wall exhaust shop to get a quote for cutting out the glass packs, welding up a new y pipe, installing a new stock exhaust can and running it out behind the passenger rear tire. The owner of the place came out, crawled under the truck and quoted me $160 out the door! Not only that, he said he’d do it right then while I waited. 2 hours later I was done. I had him look at the exhaust leaks but he wouldn’t touch them. I guess I’d have to fix them myself.
After reading a dozen exhaust threads I decided to go for it. In hindsight, I hadn’t read enough. First I thought I’d tackle the doughnut, as what I had read about the manifold bolts had me fairly terrified. They wouldn’t be named doughnuts if they weren’t harmless…right?
It was a warm, sunny day, I strolled out to the truck with my tool bucket and sintered metal doughnut. I popped the hood, looked down at the right side exhaust flange and thought to myself “I’ll be done with this by lunch!” It was 10am.
First I removed the top nut and smugly thought “Ha, I’ve only been at it 5 minutes and I’m already half done!” It was time to get dirty. I climbed under the truck and removed the lower nut. I pried the exhaust pipe back with my right hand. The exhaust didn’t move much but it looked like it was enough to squeeze the doughnut out. I reached up, grabbed the doughnut with my left thumb and index finger and gave it a tug. It only wiggled….what the heck! It didn’t make sense.
I wasted the next 30 minutes lying under the truck trying to wrap my head around the problem. I was trying to avoid the thought of having to strip down more of the exhaust train. Finally I started to further loosen the exhaust so I could pull the pipe farther back to get a better grip on the little bugger.
Flash forward another hour. I had dropped the ENTIRE exhaust train including the spare tire. Turns out the doughnut had some little insert it was riding on that couldn’t be seen until I could really pull it out. Since I had to drop the whole exhaust I decided to pull both doughnuts; they were pretty fried.
I tapped the new doughnuts on flush to the top of the old inserts. The old inserts had been in there a loooong time and were pretty chewed up but I thought I could save them. I installed the new gaskets and inserts, re-mounted the exhaust train and was so confident in my work I even re-mounted the rear tire before starting the truck. When I finally got it started it sounded like a monster truck. Both doughnuts had gross leaks. I broke the exhaust flanges loose 2 more times trying to get the doughnuts to seat. I even dropped the whole exhaust, pulled the sintered doughnuts and changed over to standard organic doughnuts, thinking the sintered were too hard to seat thoroughly.
I should have taken my time and crawled under for a close look at the exhaust manifold exit ports. The ports have a tiny recessed lip just beyond the surface the doughnut seats on. The next portion exceeds my technical writing skills but I’ll try my best to explain. The flared portion of the insert fits into the exhaust manifold port and seats on that recessed lip. The non-flared end of the insert fits into the flared opening of the exhaust pipe but no farther than the first couple inches as the exhaust pipe narrows down. I thought that if you could gauge the distance from the flared edge of the insert down to the flare shoulder and press fit the doughnut with the right amount of edge showing, the exhaust pipe might actually press forward to hold the insert against the recessed lip as well as the doughnut. Time to get new inserts made. I gathered them up and headed to my new favorite exhaust shop. I showed the owner the old inserts, handed him the measurements and asked him if he could fab new ones. Ten minutes later I had new inserts for 5 bucks. He actually flared the pipe with the doughnut in place so it was a really tight fit.
I had to go through a couple of trial and error installs while trying to get the flared portion of the insert just the right length. I ground the leading edge down until I had a perfect press fit insert between the exhaust pipe and exhaust manifold port. I finally got both inserts just the right length and have logged about 500 miles without any doughnut leaks. My 2 hour job ultimately turned into 2 days.
Time to tackle the right side manifold!
The manifold was leaking real bad from what appeared to be all 4 ports. It looked like it still had the original metal shim that was put in at the factory. I could also see areas of the metal shim eaten away from many years of leaks. I hoped the manifold surface or worse yet the head surface wasn’t damaged or pitted too badly.
I heeded the advice on FORDification and spent a few weeks hosing down the manifold bolts with penetrating oil. I used Kroil and it ultimately kicked a lot of ass.
I pulled off the heat shield and started with the top right stud. As read on FORDification, the 14mm wrench was just a touch better fit. I gently threw some weight into the bolt and it didn’t budge. This stud was nearest the worst leak. You could see what looked like the original lock washers that had kind of corroded together and better resembled a little piece of charcoal. I decided this was going to be a long day.
The key to these bolts is to not get impatient. After about your 100th push and pull effort…with zero movement…..on the first bolt, the natural male tendency might be to shout some random profanity, Hulk out and twist the little **** clean off. That’s how I felt anyway. Another 100 push pulls later I thought I saw the tiniest movement around the charcoal bits. Another 100 push pulls had the bolt swinging in a 1/4” arc. You get the idea. Fortunately, this turned out to be the worst bolt to remove. The others were very difficult as well but not near as bad. For the record, if you have a good assortment of extensions you don’t have to remove the starter to get to the bolt behind it. All total, the 8 manifold bolts took me the better part of 4 hours to remove. Here is the first stud. Notice the cool taper.
Once I had all the bolts out I was anxious to pull the manifold and make the damage assessment. Here are a couple pics of the manifold and what was left of the metal shim.
The worst damage was definitely around the 1st port, with all 4 ports showing varying degrees of blow by. Notice the varying widths of the port faces. I’m not sure if this is a product of the casting, exhaust gas erosion or both. Time for a trip to the machine shop.
As with the exhaust shop, I was really lucky and found a small mom and pop machine shop that took me right in, looked at the manifold and said they would knock it out in the same day for $25.00. DEAL! I came back a few hours later and picked it up. The port faces were so badly warped and pitted they had to take 20 thousandths off just to get back to flat. They did a great job; I didn’t even need to remove the hot air tubes for the auto choke. They worked around them.
While I was waiting for the machine shop I went bolt shopping. I ended up getting grade 8 bolts and washers from ACE. I found an exhaust stud kit on the shelf at NAPA that had the 2 odd studs in it. They were a little long but worked great.
I rounded up a bottoming tap and gently worked it in and out of each hole til they were all smooth.
Due to some surface pitting around the actual head ports and after reading a lot of opinions on the site I decided to go the doubled up Felpro gasket route on re-installation. I applied a liberal amount of anti-seize to the bolts and followed the tightening sequence as stated in the manual. I borrowed a digital torque wrench from work and torqued them to spec, ran the motor for a few minutes to heat them up and re-torqued them. I’m currently at approximately 300 miles and the truck is purring like a kitten. I love cruising along, barely able to hear the motor. I know there is debate over how well the double gasket technique would hold up. I’ll be sure to report back as I rack up more miles.
