I have a 1973 F-100 with a stock 360 engine in it.The passenger side rear top bolt on manifold is broken off.Bad thing it appears to be broken off flush with head!I have already went to three good mechanics and they turned the job down!Has anyone else been here with this problem.I am thinking about fixing it myself but afraid I will get over my head real fast!I have already been soaking top bolts with PB Blaster.

 

Flush with the head isn't typical, but it's good. just pull the manifold and soak the broken bolt a few days. then get some vice grips on it and work it back and forth until it loosens...or breaks.

Chances are in the process you'll break more bolts and they may break flush that's why the mechanics don't want any part of it. question is , do you ?

 

A previous owner broke that same stud on my 390. Their solution was to drill it out and use a 1/4-20 bolt and nut. Unfortunately, they drilled far enough off center that I couldn’t re-drill and and tap for the correct threads nor use an insert so I opened it up to 3/8” for a 3/8” bolt and nut.

With the head on the engine, access is not good, especially if you have AC. If you don’t want to or can’t remove the head and you are willing to spend time being uncomfortable, you can do as the PO did to my engine. You might want to look up the OTC tools 6982DGS. It’s a jig meant to help with drilling things like exhaust manifold studs. It’s quite spendy at $100 but if you want the best chance at getting the hole centered with the head still on the engine, it might be worth it. Or you could get a piece of flat stock and make your own.

Michael

 

I can get it to puddle up a little at the end of the broke bolt and maybe hoping the BP Blaster will work wonders!I was just wondering by chance I know it is a long shot if I could possibly take a punch and get the broke bolt to come out top of manifold?I guess the broke bolt probably does not have threads all the way and this will not work?

 

There are a couple of things working against you in driving the broken bolt through the manifold. The bolt may or may not be fully threaded. If it is fully threaded, it could be driven through but it's more likely that it's not fully threaded and has an unthreaded part known as the shank. The second and much bigger issue is that the original bolts didn't go all the way through which left a thread or to in the manifold directly exposed to the atmosphere. It's very likely that these threads have rusted badly which causes the diameter of the hole to close, making it nearly impossible to drive even a new bolt through them. I had to dig through my taps to find one with a long enough taper to slowly rethread through that rust. My standard set tapered too quickly and would lock up almost right away.

There's a bunch of ways you can try to get it out or at least get enough clamping force to get a good seal.
You can use a right angle drill, starting with a small bit, say 1/8" and do your best to keep it on center. A drill bit known as a center bit may be of some use here, they are very ridged and have a different cutting edge so they tend to wander less. Then step up in size to fit an easy out. The odds are good you won't get it out with an easy out but it could be worth a try. Penetrating oil and or heat may help with the easy out.
If the easy out doesn't work, you can continue with drilling to install a Helicoil insert. This is an excellent repair if you can make it work, Project Farm on YouTube recently did a comparison and the insert was a stronger connection than the base material.
If the insert doesn't appeal to you or you can't get the hole the correct size, you can continue drilling to 3/8" clearance and use a nut and bolt. You will want to take care that you don't over tighten it as there might be a risk of breaking the ear off the head if the manifold is warped.
If you have access to a mig welder and a welder with experience, it may be possible to weld a nut onto the stub. The heat of welding plus the use of a wrench can sometimes get a broken bolt out. If it's broken off too deep, this won't work.

Since I was replacing the head gaskets, I used my drill press to drill a clean straight hole through the 4 or 5 studs I broke taking it apart to the point that I could run the correct size tap through. Except for that rear passenger hole, which as mentioned was too far off center to be usable as a threaded hole. That one I clearance drilled for a 3/8" bolt. The intake and exhaust sides seem to be parallel, at least enough so that this worked for me.

Having said all this, it is super critical that both the head and the manifold gasket surfaces are as flat as they can be. Cranking the nuts down to fix an exhaust leak is just asking to have issues with the nuts or studs later and you can run the risk of cracking the manifold. I went very old school on my rebuild. I think the largest gap was in excess of 0.015". I don't think there's a gasket made that will reliably seal that. I spray glued an 80 grit 4" wide sanding belt to a piece of phenolic covered plywood (MDF would also work) and dragged the manifolds back and forth for 15-20 minutes each till they were within .002" of flat. I also did the exhaust manifold side of the heads as they were out a bit also. It is super easy to round the ends by pushing the part off the edge of the sanding board or grind a angle into the parts so care must be taken when doing this. The exhaust side of the head is the only part I would do this to, the other sides have critical dimensions and surface conditions. The result is that I can run the factory steel exhaust gasket/heat shield without leaks at the factory torque on the nuts.

Michael