Started to put full exhaust on my Buick 350 this weekend, including some headers, and ran into some issues removing the original exhaust manifolds. Soaked them in pb blaster, heated them with a torch, did heat cycles but running the car then applying penetrant but I still broke the 2 bolts I tried to remove. Was looking for any advice yall got to remove the bolt without turning them to studs.
Its not a matter on IF your going to break them, its a question of how many are you going to break. No matter what procedures you use, invariably your going to break a few.
If there's a choice between breaking them off flush vs. cutting the hex off and being able to get the manifold out still, then leave the shank so you have something to work with after removal. If the torch you mention is oxy-acetylene then you should have zero problems removing them from the head.
We were using a propane torch but I'll see if I borrow a buddies oxy-acetylene torch. That should get it plenty hot. Related question, for these manifolds are the 'top' 4 the only ones that aren't blind holes into the head - meaning are the top 4 the only one with the tail end of the bolt exposed? Is that what makes them seize so bad?
The ones that go through the ears are the ones prone to breaking. The exposed threads rust up. The ones in the blind holes tend to come out no problem. Propane is not going to cut it. You need to get the ears cherry red. Even so, Ive had the bolts snap
No need to break the bolts, if they don't show signs of budging...spray some penetrant into the heat to draw it in and let cool. The old timey method was to heat and wax, let cool and remove the next day. Might not be suitable for repair shops esp. when they charge for the carnage and repair, but machine shops still do this for stubborn plugs in castings. They come right out when they cool. The other method is to heat the steel bolt (with the head cool) and when the bolt is almost melting you can back it out. You only get one shot at that though before it peels the threads off. The in-car last resort of removing the broken off bolt or remaining threads when head removal is impractical is to heat up the steel as quickly as possible (before heat soaking the iron) and hit the oxy for a second. It will blast out the molten steel without harming the iron due to it's slow heat rate. You'll see the stud get red hot very fast right inside the iron before you hit the O2. This is easier to do with stubborn manifold flange to exh. pipe studs where the stud hangs nearly vertical to the world. The steel drops out right onto the torch tip and you, so you have to be fast about it and move the tip aside when needed. There's just enough time before the heat soak that if a steel glob extinguishes your flame, you can flick the glob aside and put the tip against the cherry and continue.
I got super lucky and removed all the bolts without any breaking off. Meanwhile, on my other 350, I broke about every single one. it's really hit or miss. I used PB blaster handheld propane blowtorch, and a claw hammer (couldn't find my 3lb sledge). My process was heat, PB, smack, cool. heat, PB, smack, cool. And working it back and forth with a 3/8 drive foot long breaker bar. Squeakiest damn bolts I ever heard.
Another comment on the acetylene torch... If the bolts are breaking, the work isn't hot enough. When heating a bolt up that doesn't want to budge, it can be near melting... bright and sparking.
Fortunately for me, we pulled the engine (it was planned) and used a BFH to smack the manifold bolt heads. All but one bolt was removed. That bolt we had to use a torch. No broken bolts! A little anti-seize on installation cured the seizing problem for removal several years later.
Never woulda thought of using wax, guessing it just gets between the threads and acts as a lube? Found a place that'll rent me a torch so that I can get these bolts hot enough to back them out.
If they feel creaky moving with a vise grip, they need a little bit more heat, go easy on the arm. (That's if you can't wait for penetrant) They would be starting to grab as they cool and tough to tell if close to snapping if you put some butt behind it. Always tough to do with the manifold attached vs. removed because it's in the way of where you aim the heat usually. I hope I don't make this sound too easy. Don't destroy your castings
If you can't get an oxy-acetylene torch, map gas burns a lot hotter than propane. Worked for me only broke one bolt, the one behind the power steering pump. Was lucky enough to be able to drill it out in the car with a right angle drill and short drill bits. Heat cycling and penetrant also helps. Good luck.
as he said just bite the bullet and cut the heads off, remove the manifold and now at least you have something to grab onto. heat the studs cherry red with your torch and let them cool for just a second, give them a little whack with a hammer and start working them back and fourth very gently with some vise grips. once they move even just a little you win, keep working back and fourth and they will turn more and more each time. sometimes you must go forward before you can go back.
Here is was 16 year old me did. Mind you I had very limited resources (not limited enough I couldn't afford headers) and was working on the vehicle in my aunts garage where I stored it for the winter. I did the heat cycle penetrating oil trick and it worked on most bolts. The stubborn ones I heated the area as hot as my little propane torch would get and then I grabbed a huge chunk of ice from a bucket outside (Michigan winters) and held it to the bolt to cool it down as fast as possible. My goal was to shrink the bolt faster than the head cooled and pull the two away from each other. On others I iced the bolt head and heated up a metric socket till it glowed and pounded that sucker on there. Not saying this is the best advice but I didn't break any bolts and my dad still has a metric socket that has a rainbow reflective finish on it.
