Exhaust Manifold Bolt Blues

[JeffMcKC]

I heat the head up and cool the stud spray it down with pb to cool it then come back to it seems to work

[mlcraven]

Unreal..... I just finished taking out all the bolts on one side of my 390 FE project.

Kids birthday candles are a easily accessable source of wax, I find them in with the wife's kitchen stuff.

When you can get to it (like on the flange of the FE exhaust) I prefer to heat the cast iron instead of the stud/bolt. It took 2 heating/cooling cycles (no quenching!) before the manifold let loose of the bolt, and on the third cycle vise-grips and wax barely started to budge the threads loose.

Be patient, and work both ways, loosen a bit and tighten a bit. If you do only loosen you will twist it off again. Use wax, just touch it to the tread area and watch it dissappear. If it smokes off instead of penetrating, wait a bit and try again.

It took lots of little "bites" with the vice-grips to get that one bolt that is recessed next to the exhaust dump flange, but it came loose easier than the rest for me.

Still have to do the other side, that manifold was cracked in 3 places, so a pair of hammers broke it up and off the remaining bolts. I had already cut the heads off with a cut-off wheel, that helped a bit.

Ready for another round of heating and waxing this weekend!

Good luck! That WILL come out, keep at it!

Thanks for the encouragement Stiney. With all that heating and waxing the ladies must love ya!

[TC]

Lot of talk about heating the bolt, that is great when the bolt still has a head on it, but when it's the threads of the bolt that are in the head/block, you heat the block not the bolt.....Heating the bolt will make it expand and actually make it harder to extract.......Jeff has a good idea in spraying down the bolt with PB to cool it after heating the area around it...........I just wouldn't heat the bolt/stud directly........

[Barry Donovan]

After you get tired of rounding them off you'll cut them flat & smooth. Center punch them. Drill a very carefully centered small diameter pilot hole. Then drill them out to the specified minimum diameter for a 3/8 tap. Retap and repeat. I have Willie do them on the Bridgeport - probably a couple each week. You can do them with a block of scrap drilled as a 90 degree fixture to keep the bit going in straight....

that is the real way.

to know the depth of bolt, go in all the way with final drill, whatver it may be. this relief of pressure makes it unstuck..could even use a screwdriver if no easy out.

[DanStokes]

Actually, the best way is with an EDM (electrical discharge machining) machine. It's sort of a highly accurate plasma cutter that can actually follow the threads and take none of the parent metal. EPA had one and it was worth it's weight in gold.

Dan

[min301]

Alot of good machine shops use this method.

[OldMachinist]

The theory with heat is heat the bolt so it expands and makes clearance when it cools. While still hot add parafin for lubricant then when bolt cools back it out. If bolt is flush weld a nut on bolt to have something to turn bolt with. You need to let the metal cool before attempting to remove.

[PT Sportwagon]

I guess I was lucky. When I put the headers on the wagon. I was able to get all the exhaust bolts out with out any problems. I did shoot them with wd40 a couple of times before I did the swap.

Tim

[Barry_R]

EDM is the shiznit for sure. Not something isn the average tool kit though....

[DanStokes]

I don't know how common EDMs are getting to be now. I haven't gone hunting for one here in Wilmington as I haven't had the need.

Dan

[Huskinhano]

I like using heat myself and I've drilled out many as well. Anyway my comment is to make sure you use anti seize when you but a new bolt in so you won't have to go through this again. I love that stuff!