tick tick tick my leaking manifold?

Hello,
Im working, cussing, working, cussing, etc. on my 70 skylark 350. Im on the passengers side with the exhaust manifold. Luckily its the very front. It has been ticking a leak for a few months so I decided to replace the gasket. Im not able to loosen up all the bolts on the exhaust manifold. I was able to loosen up the front 2 as well as the center top 2 only. The lower bolt on the center just wont budge, and im afraid of breaking it off, any tips? I have been able to slip the front gasket in place a little bit at a time. It still doesnt look like it all the way in place. Any tips before I tighten it all back up to start it up? Im hoping to finish it up this holiday weekend. Merry Christmas! Drew in S.C.

 

Suggest a Change in Your Plan

Use mouse milk or a similar product to work into the threads for a day or two . You may have to try to slightly tighten it first in order to move it c clockwise. Heat as a last resort.

What you are doing imay not solve the root cause for the problem if like 455 s your engine came without gaskets. So you need to remove the manifold, use an emory wheel on a drill to lightly remove any deposits or material from the engine side. Same on the exhaust side but it would be best to have the manifolds resurfaced on a table. It is cheap and will true them back flat. Also it will give you the best look for cracks which are common. This could be your problem as they open with the heat and atart the path past the gasket. Look closely as the cracks are subtle when cold.

Finally install new hardware from ARP. Using the old stuff invites breaking off a bolt.

 

If the exhaust manifold bolts break off, and there are some threads hanging out, use a file to create flat spots on opposite sides of the broken bolt and soak with liberal amounts of penetrating oil, PB Blaster (or even mouse milk though I have never heard of it).

Heat the area with a propane torch (not the broken bolt) hit the end of the bolt squarely with a hammer and use vise grips to twist on the bolt. The flat spots on the surface helps to twist the bolt, and not just rotate creating scars. Often welding a nut on the end of the bolt is real effective.

I use a 3 inch wide by 24 inch long belt sander with medium course paper to carefully resurface the manifolds taking irregularities that are in the surface from using gaskets. Then reinstall without any gaskets, as that is how the car was probably built in the first place. Cleaning the head surface as flynbuick suguested is a good idea as well.

Using at least Grade 9 bolts (ARP fastners probably better, but more expensive) and antiseize (copper or gray your choice), have not had any exhaust manifold leaks with this procedure. Make sure you retighten the bolts after you warm up the engine and after a couple of heat cycles.

The great part about using antisieze on everything reassembled on the car, means that the next time you need to disassemble the bolts come out easily.

 

Thanks for the ideas. Im trying this tomorrow. i wont be able to take the engine out of the car. Looks like maybe I can get the center exhaust bolts through the wheelwell area. Was hoping Santa would have brought me a engine hoist. Thanks again! Drew.