79 CJ7 304 exhaust manifold bolts

[mriplaybass]

We have given up on the POS headers that this jeep came with and opted to go with stock cast iron manifolds. The holes in the cast manifolds are rather large considering that the heads are threaded for 3/8" bolts. Are there inserts that go in the over size holes for the 3/8" bolts to go through? or is there just supposed to be that much "wiggle room" for the manifolds to be positioned?

 

[Lumpy Grits]

Have you tried a 7/16" dia bolt?
LG

 

[mriplaybass]

I used 3/8" bolts to hold the manifold in place to do a mock up, plus the header bolts were 3/8". I wonder if there might be some sort of shoulder bolt that was used originally. 7/16" where it goes through the manifold, but 3/8" threads to go into the head.

 

[Torxhead]

Sounds like someone could have reamed out the clearance holes in the manifold. Maybe you should install all of the bolts to determine just how much "Wiggle room" you have and go from there.

 

[mriplaybass]

Actually, the manifolds are bran new.

 

[Lumpy Grits]

I would not use bolts. I would use studs that bottoms in the holes, in the head.
LG

 

[mriplaybass]

That's kind of what I was thinking.

 

[Torxhead]

Yeah, I would go for the studs also. Knowing that they are brand new is interesting. From My little experience cast iron manifolds do move a bit after they get hot making it a bit tougher to line up all the holes. If you could get hole reducing sleeves or custom studs in there that might work but make it tough to remove after they are on for awhile. So maybe get 3/8" grade 8 studs and nuts using thick flat washers and that would be just fine. There are aftermarket stud kits for this I believe.

 

[mriplaybass]

Well, here's the latest kicker! I figured I would put the manifolds on with just 2 bolts in order to fab up the rest of the exhaust system, and stud the heads when I was ready to do the final install. I did not notice earlier that the 2 bolt holes for the center 2 cylinders are actually 3/8". The outer 2 cylinders have the enlarged holes. Maybe this is for the slight movement that Torxhead stated? So I think that all is well. It took some wiggling, but eventually the drivers side manifold went on. However, I don't think I will be able to remove the back spark plug without removing the manifold! When I moved over to the passenger side, there was no way to get more than 1 bolt in at a time! I took the manifold and laid it against the hedman header that I removed and the bolt holes lined up. When oldjeeplady came to help me before I launched the manifold into the back yard, she noticed that the manifold was hitting the head bolts! I don't want to start grinding on the manifolds since they are new, but other than using 2 or 3 gaskets, I see no other way. Also, I don't think that the front spark plug can be removed without removing the manifold on the passenger side, or grinding some relief into the manifold. These are Omix-ADA manifolds. Just some more junk from China? or did I just get some bad ones? Has anyone else used these manifolds?

 

[Torxhead]

Thanks for the update. Sometimes you have to just think these issues out and you can come up with a solution. Hopefully somebody will chime in and come up with something.

 

[Lumpy Grits]

Omix-ADA=China !......
LG