finishing up on lots of exhaust work. The manifold to exhaust pipe flange was leaking again. I had double gaskets in there which had helped for a while. I knew it was goobered up. Earlier I had tried grinding the exhaust pipe flange flat at the bolt holes but double gasket was the only way to keep it from leaking. I knew I had stripped some of the threads in one of the manifold stud holes at the exhaust pipe and it was going to be a pain to work on. So I took it to a near by muffler shop thinking that if I just threw money at it they would make my problems go away.
I bought the aftermarket flange off
ebay, thinking they could weld it to my toyota downpipe. Also brought them new toyota studs and nuts and new flowmaster muffler. When I went to pick up the truck, the exhaust sounded terrible. I drove it home and the next day checked it out. I had a terrible leak at the manifold and a pea hole at the top of a weld at the pipe to muffler. I took it back and they fixed the weld leak. But the leak at the manifold they said was coming from the heat riser joint. Ugh!
The muffler shop threw my original pipe out. Ugh! They bent a new aluminized pipe and totally re-engineered the flange connnection. They flared their pipe and left the flange loose. Later, when I removed my manifolds I realized they re-drilled the manifold stud hole and re tapped it with coarse threads! They did this while on the lift. Twisting their necks to look up...the hole ends up being about 15 degrees off of square. They also wallowed a hole in the brand new flange to get the tilted stud to go through it. All this without a phone call to consult me.
I went back and argued with the owner but of course I couldn't get anywhere with him. In the end I realized that I had to fix this myself...due to the leak at the riser joint.
It took it home and took it all apart. Ordered all new gaskets a block off plate for the riser and some new hardware too. I managed to get all apart without wringing any bolts or stripping anything. Several days of spraying( EDIT: PB blaster ) helped loosen things up.
I had a spare exhaust manifold I had bought off Willard a while back and it had good stud holes and the heat riser valve retaining bolt looks better and not pitted like mine. So I used his manifold and bolted to my intake. I wanted to get the heat riser joint machined flat but the contour in the exhaust manifold prevents this. In the end I just got the gasket material off and cleaned up the surfaces with a die grinder and abrasive pad. The machinist who worked on my head told me about a trick to remove the remaining metal gasket material that was sticking to the cast iron. Tapping with a ball peen hammer while hitting it with a torch flattens out the metal and it breaks loose. Pretty good trick I though. At first I thought my heat riser insulator was good but upon further inspection found a slight crack in it at the corner.
So I opted for a Cruiser Outfitter block off plate at about 1/2 the price of a Toyota insulator. I struggled with this decision. The Block Off plate pins the heat valve open always. As in always angled to deflect the exhaust down and out the exhaust pipes. This keeps it from warming up the intake ...making a longer warm up with less atomized fuel in the warm up stage. But the advantage is that the intake manifold will never have the dreaded crack developing the bottom of the bore ...below the carb.
Following advice found here on the forum, I loosely bolted the manifolds together, making sure I had flipped the heat riser valve to the hot position. You have to reach through the exhaust manifold and turn it to the hot position and while holding it there with your thumb in the exhaust pipe hole, bolt everything together...both gaskets and the block off plate. Once done, I put it on a spare cylinder head I had on my bench and then tightened up the joint. Then off to the machine shop to work on the cylinder head to manifold surface and spot face the flanges where the bolt heads rest.
this is getting really long, I'll follow up with some pics and a few other details.
. Fortunately they seem to stop bothering me at some point.