I'm looking for advice on what to do. I'm cleaning and detailing my 300 engine taking off brackets,pulleys etc. I decided to try and remove the exhaust manifolds. The very 1st bolt head broke off with little force on the front drivers side. The broken bolt is still in the manifold and head only the bolt head sheared off. I'm afraid if I try anymore the same thing will happen to the rest. Should I just leave it alone or ?
If it’s a bolt that is broken off in head you may need to remove head. If your a decent welder, you can try to weld a nut to it then turn that to try to loosen. Otherwise remove the manifold, so you can get to bolt, heat with torch oxy-acetalyne. Propane aint gonna do it .
This is a very easy problem to solve. Take a torch (I use map gas handheld) heat the exposed portion of the bolt as hot as you can get it and while it's hot squirt a little bit of penetrating lubricant where the bolt intersects the head and let it cool down and then once again reheat the bolt and the casting on the head as hot as you can with that torch and then grab the bolt with a pair of vice grips and slowly work it back and forth and it will come out easily.
If any of the bolt is sticking out of the head you can try what GSS said above. If it's broken off flush you'll need to either weld a nut to it or try to drill/tap it out. Either way you'll need to take the manifold and maybe the head off. You might soak the other bolts for a few days with Blaster or Kriol and then warm up the engine before you try to loosen them. Don't just turn them, rock them back a forth and every time it will turn a little more until it starts to turn complete rotations. The studs that hold the header pipe to the manifold also need to be soaked and rocked.
On exhaust manifold that's never been off before I always hit the bolt with heat before trying to remove it. this breaks the bond of rust, also the expansion and contraction typically loosens the bolt up to where it comes out fairly easily
Soak all the bolts with PB Blaster for a week, warm up the engine, shut it off, let it cool a few minutes. Take a ball peen hammer and smack each bolt with a hammer firmly once. Then try to loosen each bolt 1/8 of a turn and tighten it back up. Soak it with PB blaster again and repeat. Slowly back them out until they either break or come out. Once the manifold is removed you can then you can try heat and vice grips to turn them out. Use a grinder to make two flat sides of the remaining bolt so its easier to grab with the vice grips. Its often easier to take the head off and bring it to a machine shop, they don't charge too much most of the time.
I'm afraid that if you don't fix it you will get a leak. Also, don't forget to soak the back side of the thru bolts.
I've had some success with drilling and re-taping, then using new Stage 8 bolts with lock washers. Also, I didn't use gaskets, just some copper gasket in a tube. Having said this, I have taken my front sheet-metal off, so everything is easier.
Thanks I had to drill and tap 3 of them. I bought exhaust manifold gaskets but my car didn't have any on there when I took it off so I don't think the factory used them.
But once the manifold is removed you should use a gasket unless you want to mill Both the head and manifold mating surfaces..
Hmmmmmm I don't agree. You can use a gasket but it will blow out in "X" years. The rate of expansion is different for the head and manifold. That's why the factory did not use one. You can get the manifold flattened if you can find a shop to do it. Prices range from $30 to $60. I would not worry about the head. Use the copper sealant mentioned above. Sandblast it first and put a nice finish on it.
Since you are detailing the engine I think someone on the board sells correct bolts - maybe Todd has them for the 300.
Use these gaskets and I guarantee you will never have a leak and you will never have to tighten the bolts ever. http://catalog.remflex.com/BUICK_Header_Exhaust_Manifold_Gasket_p/13-010.htm
I had a truck with cheap headers and they leaked no matter what. Switched to Remflex gaskets and 20 years later no leaks.
