Repairing Exhaust Manifold

[Cutlass]

It appears the one or more prior owners drilled out the old exhaust manifold studs (the six that connect the down-pipe), and re-tapped the holes at 3/8-16, instead of the original 5/16-24 size on my '66 BJ8. A couple of the holes are too buggered to hold any sized stud. I'm aware of the heli-coil option, but wanted to test the deep waters of knowledge contained here to see how others might have tackled this issue.

 

[Keoke]

Hi Cutlass, Time permitting you might try Ebay I recently purchased for very little money an excellent set of exhaust manifolds.Otherwise, it seems your only other option is to use an insert type thread repair kit.--Fwiw--Keoke

 

[Cutlass]

Thanks. I've been looking.

 

[tahoe healey]

I got a nice set form British Miles for my BJ8. Blasted and painted like new with studs fit and ready to go. Its hard to find a good rear one for a BJ8 apparently. The flangs break if you don't have flex tubes of the exhaust but they have alot of front ones. Thats what several used parts suppliers told me. If yours are good, keep them and fix the studs.

 

[Cutlass]

Mine are just fine, except for two of the three stud holes, which are, as we say down here, "wallowed out." Apparently, in order to get one frozen stud out, a po drilled down from the top, at an angle of course, leaving an oval hole that really doesn't fit anything. I was thinking of enlarging the hole from its present minimum 3/8" to 1/2", inserting a 1/2" plug, then re-drilling the correct 5/16" hole for tapping. Sort of a poor-man's helicoil.

 

[jlaird]

You do know manifolds can be welded up, redrilled and taped or what ever. Even broken ones can be repaired and if done properly can hardly be noticed.

Now that said, have it done by a specility shop.

 

[Cutlass]

I have heard various claims of ability to weld cast iron, but am very skeptical, as I have yet to have someone actually relate personal experience. If anyone actually knows someone who has really done this successfully, I'm all ears, as that would be a great solution.

 

[John Loftus]

Here's a video showing the technique with a henrob torch ..

https://www.cut-like-plasma.com/info_welding_cast_iron.htm

Cheers,
John

 

[jlaird]

The big valves that the oil companys and the paper plants furnaces use are cast iron and they weld em all the time at the overhaul shop.

 

[DougF]

Another option would be Keen serts. These are far better than heli coils. You should be able to find them at better auto parts stores.
The hole has to be drilled and tapped to size. Thread in the Keen sert(which is similar a hollowed out set screw that is threaded both inside and out). They have 2 or 4 tines (depending on which duty you get) connected to the outside of the insert that are then driven into the threads of the piece. These were originally manufactured for aluminum heads with cross threaded spark plugs. The fix is permanent, but the inserts can be removed by drilling, tapping the tines away from the threads and screwing out.

 

[GregW]

Hi Cutlass,
Just saw a set of manifolds on E-bay. manifolds

 

[Cutlass]

Thanks for the tips. The e-bay manifolds are the earlier part numbers. My car is a '66 BJ8. The Keenserts are new on me, but they look perfect for at least four of the six problem holes, and might even work for the other two. Great tip!

 

[bighly]

Once repaired you might consider jet-hot coat to protect, seal heat, beautify and hide the repairs.

 

[Cutlass]

You're right. I did the same with my MGB, and it's great.