While trying to remove the intake manifold from an old Ford 302 one of the bolt snapped off. As you can see below it is just about flush with the manifold (just below.
I would remove the remaining bolts if possible, and attempt to lift the manifold off enough to rotate and clear. If it works, use the penetrating oil and heat as previously suggested then vice grips on the bolt shaft. Caution on heat, turning while very hot will just twist off the bolt again.
I would say the best option here would be to use a screw extractor, which will involve some drilling. The steps to using it are as follows:
- carefully drill a pilot hole in the bolt
- twist the screw extractor into the hole
The left-handed thread of the screw extractor will have the effect of loosening the bolt as you try to force it into the hole.
Here is a 5-minute video on how to use a screw extractor.
I had a similar problem with a Landrover Discover exhaust manifold stud. I carefully welded a washer and a nut onto it. You can see it here - http://handyhowie.co.uk/handyhowie/Disco_1999_Exhault_Manifold.html I think the heat helped it come out too. One thing to note however, is that the discovery had an alloy head.
I think that the hole in the intake is not threaded and the bolt goes through the manifold and threads in to the head. If that is the case you should be able to pull the manifold off and then address the stuck bolt separately. A good soak with PB Blaster always helps and the previously mentioned trick where you weld a nut on to the top of the broken bolt works surprisingly well.
The bolt extractors should really be a last resort. The extractors are much harder than the original bolt, and if that extractor breaks off inside the bolt, you just made your job a lot more difficult. Drilling through normal manifold bolts is cake compared to drilling out an extractor. The drill bit wants to drill through absolutely everything except the extractor, whether that's the original bolt or the head.
Extractors can be nice if the bolt sheared off (e.g., you dropped something on the head and it broke sideways), but if it initially broke off because it was stuck in there really tight, the extractor isn't as likely to work.
If you're going to try the extractor, don't put a lot of pressure on it. Just try heat and lube and put moderate torque on it. The bigger of a hole you drill in the bolt, the better off you are. You can use a larger, stronger extractor, and there's less pressure holding the bolt in place.
If you are going to do any drilling to get it out, use a left hand drill bit, it usually will unscrew the broken bolt. Works great.
These heavy duty spline style screw extractors should do the trick. These spline ones are the only screw extractors I've ever had good luck with. I've broken just about every type of screw extractors you can think of (cheap and expensive ones of various styles) and these are the only ones I've found to be worth a damn.
I did break one of these once, but I put a lot of torque on it and it wasn't real deep in the bolt. I still have the majority of the shaft and it's still useable :)
I had the same issue. I removed the manifold completely and tried to remove it with vise grips without success. Then it broke again and was flush with head. Then I drilled it and tried an extractor which did not work. My last resource was drill the whole bolt starting with a small drill and switching gradually to a larger one. Then when there was a thin wall left from the bolt I drilled with a tinny drill bit between the bolt wall and the head wall. Damaging the thread on the head a little bit but was able to remove the bolt. After that I drilled a larger hole and fixed the thread with a helicoil from autozone. Be careful not to break the drill when drilling the bolt otherwise you will be screwed. Good luck
Peter & Fred are the only ones who are giving good advice here (surprisingly not being upvoted?). I'm pretty sure that on a 302, if you remove the rest of the manifold bolts, the manifold will lift straight off, and there will be 3/4" of bolt sticking out. Clamp on to this with a large set of vice-grips, and turn the bolt out.
If the vice-grips slip, clamp them on a little tighter, and hit their handle with a hammer such that they turn counterclockwise. The impact action may work better than just turning.
I'm pretty sure that this will work, but if not then welding a nut to the shaft of the bolt will be a lot easier with the manifold removed.
The manifold itself is probably stuck to the gaskets, so you might need to hit it with a hammer to break it free prior to lifting it off. Sometimes there is a protrusion in the manifold where you can get a prybar in between it and the block to pry up, without prying in the actual gasket area; don't be tempted to insert anything in between the manifold and the block; (ie. hammer and chisel) if you mar the mating surfaces the new gasket will not seal, and you will have a vacuum leak.