Replacing exhaust manifold engine block studs

Help! Newbie here with some questions. I need to replace a few of my engine block threaded studs for the exhaust manifold on my 54 M38a1's 4 cyl F-head, and need some help. Ordered the new stud kit and will be replacing all of them if possible, along with the manifold (with an aftermarket one to save some cash). Question #1: There is some rust on the studs, some of the outer threads were pretty mangled before I got to them, so any suggestions on removing them without snapping them off inside the block. I already snapped the single threaded stud inside the bottom of the manifold itself when I removed it. I thought about some liquid wrench, but not sure it will actually be able to penetrate inside the threads in the block. Question #2: Are the studs right or left threaded inside the block? Question #3: What tool would you guys suggest for turning the studs out and replacing them? Just vice-grips? Questions #4: IF I get the studs out successfully, do I need to put anything on the threads prior to installing the new ones? Blue Lock-tite? Teflon paste? Nothing at all?
Thanks!

 

There probably could be several books written on ideas about this. Google it up and there will be a ton of info.

Nothing different or special about the F-head in this respect

 

ive run engines to operating temps and then shot some penetrating oil on there while still hot. need to wok fast and with proper clothing so you don't get burned. be careful not to put too much on as it might ignite. a torch works good but you want to heat the area around the stud not the stud itself so the metal expands around the stud. you can always break them off and hope there is some sticking out of the block and then torch it up and do the vice grip thing too. done it all these ways. a really good home made penetrating oil is atf mixed with acetone. once again be careful with this one as it is really flammable if too much acetone is used.

 

If the studs are really rusted, I usually try to cut the nut off by grinding one flat of the nut paper thin, or using a cold chisel across the nut flat to cut it. It is a lot easier to deal with a whole stud rather than a one broken off in the block. You can run a die over the threads to clean them up afterward. They are conventional RH threads.
The F-head seems to easily break studs. If you can get the manifold off, I would not try to remove the studs that can be cleaned up. The risk of breaking them is just too great.
-Donny

 

OK, thanks guys. Sounds pretty much like I feared, no silver bullets. May have to winch it on to a trailer and take it to a mechanic. If I snap the rear one, the engine has to be pulled to drill it, and pretty much the threads are crap on every stud (can't get two nuts on them to back them out either) and probably too much rust on all them to salvage them again. I can't believe the manifold/gaskets held out for nearly a year like this since it was put together (not by me). Thanks for everyone's suggestions. Teach

 

Just something to consider, you can run a die on the unthreaded portion to increase the threads and then put two nuts on it and back it out. I have had good luck with a left handed drill bitts, on the ones that broke off, most of the time it will grab the broken stud and back it out. You can find them at good auto parts stores. if you can clean up the ones that are there and reuse them I would do that, on mine the rusty threads were only where they stick out of the nut. And like Howard said use Brass nuts when you put it back together. Good luck.

 

Thank you all for your tips! I am happy to report...success! All of the studs came out today, didn't snap a single one. I sprayed them with freeze CRC spray and let them soak over night. Then used a small pipe wrench and out they came. Waiting on my new stud kit with brass nuts and the new manifold and I'll be back in business.

One last question, since three of the stud holes leak out antifreeze if I take them all the way out, should I use some teflon paste on the threads when I install the new studs? I used it on my hydraulic fittings on my wood splitter with great success.
Thanks again everyone.
Teach

 

Congradulations on succeeding where I never have that good of luck! I would have broken at least one or more studs.
I use old-school Permatex Aviation on studs going into a water jacket. I'm sure there are more modern solutions.
-Donny

 

CLP at the block, double nuts, on a short ratchet (less torque there, sore hands too), clean with clear alcohol when cool, blue thread lock

 

A few guys have had good luck by heating the stud with a propane torch then touching a Crayon to the stud as close to the block as possible let the crayon melt until the stud is soaking wet allow it to cool to the touch, Repeat. Something about the properties of the wax causes it to be sucked into the rusty threads. The two Nuts threaded against each other works. It works even better if you can use a 12pt box end wrench that you can get on BOTH nuts. You of course have to have two nuts that will get to the proper level of TIGHT with the point of one nut centered in the flat of the other (you can grind a little off a nut to get this to work) I usually have lots of various sizes of nuts so I just swap them around until it works out. This helps spread the load on the stud. once you have the nuts on the stud take about an 8oz ball pen and carefully tap hard on the end of the stud 4-5 times. Then while watching the stud where it enters the block start trying to turn it.

I like using a Box end wrench instead of a socket as it usually allows you to see more of the stud while you are doing this.

I have also had good luck using a Stud Puller but they can tear up a stud so only use one on a stud being replaced.

Get a good quality tap using it dry chase the threads then stick a magnetic probe in each hole to help pull any metal back out. I then like to dry brush the threads with a bronze rifle bore brush (cheap at the sportings goods store where they sell gun cleaning supplies) a little evaporating cleaner like brake kleen if you don't have any water or oil in the engine as a last step. CLEAN THREADS are good threads

And yes a good sealer on all the new studs when you put them back in. And only tighten them to a tiny bit past hand tight. If you feel any resistance STOP you could be to deep

 

An older thread, but since my block is dry (just rebuilt) which studs hit water jackets this needing the sealant.

 

Thanks.

 

Bumping up this old thread cause I have a few questions. I have an exhaust manifold leak at the gasket. I was about to pull the manifold but then after reading this thread I realized the PO used bolts instead of studs on all but the very rear one of the manifold. Also, Now worried about the front bolt leaking Coolant if I try to remove it.

I guess I'll be draining the coolant before attempting this but I wonder if using penetrant on the top of the bolts will even reach the threads with the manifold and gasket already in place. Any advice is appreciated. I've never done this before.

 

If you break the rear one, you'll wish you'd never tried.

 

Haha yep. I’m planning on leaving in the rear stud and replacing the other bolts with studs.
Unless there’s a reason using bolts again is better that I’m unaware of.

 

That gasket and the bolts look fairly recent, so will probably turn out without a lot of trouble.