Removing Rusted on Bolts

Have you ever tried the birthday candle? All you have to do is use enough heat to melt the candle,and let it drip around the studs into the holes.I have tried this myself on the studs on a 1956 ford truck and it work great.Dam near was able to turn the stude out by hand.Good luck.Mike Durkin

That's my suggestion.Paraffin Wax melts into nooks and crannies and is a high pressure lube. Also fixes stuck zippers:eyebrows:

I have always used Kroil oil--need to apply every other day for a week and seems to penetrate and loosen the bolt.

If you want to get done sometime soon, go ahead and use the vicegrip and torch method. Adjust the vicegrips and get a good bite and then remove them and heat the manifold around the bolt or the nut on a stud to glowing red and then quickly clamp on the vicegrips and work it back and forth. You need to quickly determine if you're twisting the bolt in the manifold or only twisting the bolt back and forth and are going to break it off. Sometimes that's a "feel" thing since you can't see the bolt in a blind hole, sometimes you can see the bottom of it.

If you can't get one to break free, I would go ahead and clip off the head and remove the exhaust pipe and then weld a nut on it, let it cool completely and try it again.

On a thin cast piece, I would be very careful about blowing out a bolt with a torch. the thin section of cast will heat up quickly and you can easily blow out the threads/hole along with the bolt. That technique works a lot better on thicker sections of cast iron with steel fastners broken off in the hole. It always helps to drill the broken off bolt/stud through first. Try your easy outs etc and if that fails, then blow it out with the torch. It's a lot easier with the hole through even if it's a blind hole in the cast iron.

My best success with broken studs and bolts that have enough exposed to getvise-grips on...is to heat up the bolt...then put ATF on it...As the metal cools the ATF will be drawn into the threads and the bolt hole...You may have to do it several times...Just take your time...Try to move the bolt a little...If it doesn't move...heat it up again...apply more ATF...It will break loose...I have done this... Waited until the next day...and easily removed the contrary broken bolt or stud...
The key is to break through the rust in the threads...
When a bolt or stud is broken off even with the surface...Heat it up...oil it... and then try drilling them out...
Easy-outs...I try them once in awhile...I find that drilling a hole as close to the threads as possible...then using a diamond point chisel...to peel out the metal from the threads...also use some lubricant...then an easy out...with some patience...works ...I use this method... though slow it always works...The broken off bolts or studs rarely go the full depth of the hole...So, there's space in there to collect plenty of lubricant...that will soak the threads through the rust...
Just Take Your Time...to Avoid Making a More Difficult Extraction...
It's the truth...so help me...
Respy, Carl

I've just always used heat. Heat it up with a torch until it's red to orange then let it cool. Heat expands and as it cools it contracts usually enough to come out with vice grips or a pipe wrench. Most of the time it works for me the first time but sometimes it may take a couple treatments of heat. A little penetrating oil can help also after it cools enough not to burn it. I just did this on my D4 exhaust to manifold nuts and studs. And contrary to some's opinion I put things back together with 'never seize'. You'll not have any trouble taking it apart next time if you have to.
Geeve um!

Often on these old critters they used high strength bolts and studs. You can drill 'em as long as you use a low speed and heavy feed but drill all the way through. When you heat 'em and then later try to drill 'em, you'll find you've tempered 'em to about the hardness of diamonds. Unless you then use a carbide drill bit, you're not gonna get anywhere with 'em. Go straight to welding nuts on at that point. I use a mix of 2 stroke oil and acetone and start soaking 'em as they cool. (Gonna hafta try the candle trick sometime.)

I start with drilling the offending bolts/studs all the way through, then soak 'em with "loose juice". An easy out is next and if/when that doesn't work I start welding slightly oversized nuts on. Let cool slightly and more "loose juice" then give 'em a whack with a 5 lb hammer after they've cooled and usually, out they come. Sometimes I've had to weld a nut on more than once.

I've burned a few out after drilling 'em but I reserve that for 1/2" stuff and up. Heat 'em up til they spark, pull the torch back and hit the oxy lever. A really clean tip is needed and a steady hand as well. After the thing has cooled, usually a file tang will twist 'em out. . .as long as you didn't burn into the threads in the cast iron.

The exhaust manifold bolts on my D2 were so rusted I tried everything. I ended up putting it on a milling machine, machining off the studs flush, center drilling the studs, drilling the studs to the minor diameter of the stud then running a 3/8- 16 tap down through,(cautiously!) that cleaned the rest of the threads out. OlGrump is right when you heat them up they get really hard. For the short stack that attaches to the manifold up through the hood I machined up a SS 3/8 thick square plate bored it to accept a piece of heavy wall 3 inch SS tubing and welded it together. That will last longer then me for sure. Fortunately at the time I had a Milling machine at my disposal I no longer have that luxury!