Iam about to replace my cracked exhaust manifold on my 1975 F-100 with a 360, The last 3 days I have sprayed the bolts with Kroil penitrating oil and wondered if They wont budge if anyone has a better idea if I need one.


Also do I need any gasket sealant on the exhaust gasket.

 

Mine were all rusted to the head due to sitting in a field for 12 years, I was lucky enough to be doing a top end at the time too, so I pulled the heads off with the manifolds still attatched. Used an impact to pull the bolts out that I hadn't already broken off, so in short, no not really a better idea unless somehow you can get an impact on them. The "banging" of it will break them loose as opposed to breaking them off like shear strength will do. As far as the gasket apparently the head and exhaust manifold are machined surfaces so you don't need a gasket, mine I put gaskets on but didn't use any sealant and I do not have any leaks. Good luck man.

 

I always cut all the heads off with a torch if they won't budge. No sence in breaking them off, then your really in trouble. Then heat around bolt with a torch and use Vice Grips to get them out.

 

If you cant break it loose and you are afraid its gonna break, torch or grind the bolt head off. Its the only way you're gonna have enough bolt left to clamp to. If the bolt breaks off flush with the head you are pretty much screwed. Machine shops can drill them out, and if necessary they can rethread it a larger size.
I also heat around the bolt, try not to heat the bolt as much as possible. Once its good and hot smear some wax on it. It runs down in the threads and acts like penetrating oil, only without the flammability. Clamp your vice grips on it and work it back and forth while your backing it out.
Finess is key.

 

Thanks for the ideas! I ordered a manifold and have not got it yet but I will try to get the bolts out now and see what happens. I have a small torch with MAP Gas, do you think this will do the trick if I need it?

 

i tried all the above tricks, and i guess finesse is the bigtime key word. had to have mine redrilled and sleaves put in for the correct thread size.

 

One my 400 I drilled as small hole through the manifold just outside the radius of the washer at an angle to get to the threads. I then sprayed PB Blaster into the hole and hit the bolt with a hammer to get the oil to penetrate further. I did this a few times a day for over a week and was able to get all 16 bolts out without having one break. There was quite a bit of gunk on the bolts when I pulled them out, but the PB Blaster really seemed to break it up. The main trick was giving it enough time to work and getting it directly onto the threads.

 

You need an oxy-acetelene torch with a BIG osebud tip.

Heat the hell out of em - REEEED HOT.

CAREFULLY work the bolt back and forth. If you're not 100000% sure it's ready to come out, more heat is in order. CAREFULLY try to back it out again.
Repeat until the bolt will come out.
I've never broken one off with this method.

 

I have learned a trick from a shop friend, and it needs to be done right,. so ,.. if you heat the manifold bolts red hot with some torches,.. then quench them with cold water,.. it might take a couple of times,. this usually will burn off the corrosion that's in the threads,.. and then take care removing them ,.. dont use air tools to remove them,. use hand tools, and only 6 point. not 12. you will have a better feel for them as u work them loose.. this way is faster. I have had problems myself over the years with thes exhaust manifolds warping and leaking. or cracking. I hope this helps..