Any advice for removing two broken exhaust manifold studs?

Here is what I have done so far:

After nasty passenger side exhaust leak I purchased new Percy gaskets, had a new manifold in waiting (didn't need it since original was fine), used PB blaster everyday for two weeks prior to removal. All 4 bottom bolts came out with ease. Top 4: All 4 broke. Two came out with double nut and patience. Two remain broken flush with cylinder head.

I considered drilling and easy outs but not enough room. I hired a welder to come over and weld nuts onto the studs for extraction. Both nuts eventually broke off from studs because there was no movement whatsoever.

I have read some use a torch to blow out the metal studs and then run a tap through the holes to clean up. I'm considering this as a last resort before pulling engine or head.

Does anyone have experience with this? What should I be concerned about if I give it a try. Any other ideas?

Thanks!

 

Any time your faced with rusty stuff heat is always your friend. You'll probably have to remove the head, drill the stud out then heat and easy out, or retap the threads.

 

I had a 352 years back with one messed up top hole. I ended up just drilling it large and using a nut/bolt through it. Not sure I would do that for a good fix for multiple holes, but it got me by for one hole.

Burning the old bolt out would be for someone with very good torch skills. If not you might end up with a real mess.

Lots of heat on the upper holes is the only way to get them loose. Sometimes that just doesn't do it either, especially after 40 yrs.

 

Torch in engine compartment = fun fun fun. I did as Freightrain, even went as far as to use stainless hardware and didn't leak there. Best thing I ever did was replace heads and go with headers.....now about starter clearance and heat issues..........When I drilled I finally found a use for that 90 degree angle drill Craftsman put in my C2 set I got for Christmas.....

 

removing inner fender might get you enough room to drill
or an angle adapter for drill ?

 

Personally, I wouldn't even begin to consider using a torch. I'd use an angle drill with a Snap-On type E1020 extractor set if you can find one to borrow.(Extracts broken screws from 1/4" to 1/2" diameter but costs $128.00) It uses a straight fluted type rod with an adapter to unscrew the bolt/stud after being drilled. It's very possible to bend/break the fluted extractor if the hole is too small for the size of the stud or the hole is drilled into the threads of the head. It's also extremely difficult to remove once it's inserted into the hole. It's sometimes a small pain to remove the stud from the extractor once the stud is out.

To get a true center to drill to, reinstall the manifold with a couple of bolts and use a "transfer punch" through the manifold holes. Drill small holes and work up in size to something close to the stud size. 135 degree split point bits work best.

This type of extractor doesn't place excessive force outwards as does a typical left handed twist type extractor. Short of the above, I'd say remove the head and leave the torch method out of the operation except for heating.

Dan

 

Thanks for the help. I do think I'm going to go the route suggested with the angle drill. Appreciate the input. Will give an update hopefully in the near future. Thanks!

 

I have used left handed twist drills also.. works sometimes.. I'd pull the front wrap instead of the heads...


Baja

 

I was working on one a few years ago with a nasty exhaust leak on the passenger side. Turned out the flange was actually warped on cylinder 3, but in the process of removing the manifold of course a couple of studs broke off in the head. I finally just decided to pull the head since I was going to have to mill the manifold surface flat anyway. Turned out the head gasket was probably only a few hundred miles from blowing out so off came both heads and a complete HG job.

I've heard this syndrome referred to as Shipfitter's Disease, where you go to do something relatively simple but it leads to other problems, which in turn lead to yet more problems and pretty soon you're replacing the whole engine when you started out to replace the spark plugs...or something like that.

 

Tiger Dan may be on to something. Your broken studs will lead to rebuilt heads IMHO. Looks like you have a 1969. AKA without hardened exhaust valve seats. If your local gas stations have oxygenated fuel (ethanol/methanol) like we do you should have those hardened exhaust valve seats. So depending on your situation and the mileage of that engine, you might jerk the heads and send them out to a machine shop to be rebuilt and with the hardened seats. Let them deal with the broken bolts.

 

2X Bajas comment about using left-handed drill bits. Many times the bolt will start to loosen up as you're moving to a larger drill bit size.

 

If at first you don't succeed, then skydiving is not for you!

Left handed drill bits have worked for me .... sometimes... start with a little one, and work up from there... be sure to get it centered as best you can..

Baja

 

I've come across a many of fe vehicles where someone has replaced the bolts with grade #5 to #8's that are to long on the upper threaded boss.
And what happens to the bare threads is rust.

They rusted to the point that the threads are almost eaten away at some degree.
When trying to back these out only end up snapping the bolt heads off most of the time when the rusted extended threads start to the threaded boss galls in it.

Using the correct length of replacement and being a grade#8

And for the little extra insurance they will come out next time if needed is to use some anti seize lube helps also.

And 2x with Jeff on just pulling the heads and getting them rebuilt with harden seats & most likely valve guides .

A shop will just drill the broken ones out and put in a HeliCoil in them. They won't take the time trying to work the broken one out as they don't have the time to baby it out.
Orich

 

I just did this last week with a 352 (out of truck). Got 6 of the top bolts out, two broke off flush with flange. I burned the two broken ones out with acetylene cutting torch. First time I had ever done it and it worked, the cast won't cut, you are just melting the bolt and blowing it out with the cutting oxygen. Use a thick piece of metal behind the hole as a heat shield to keep from burning your valve cover gasket, and remove the spark plug, the heat will crack it. I used a center punch to clean out as much slag as I could, then ran a tap through the hole. Here's a video I found of it being done on a Dodge.

 

He burns out the broken stud at the 16:10 mark.