Intake Backfire:Doing intake & exhaust gasket Exhaust stud busted off flush w/ head

[Ben's Z]

While investigating my intake backfire I noticed out of the cylinder closest to the firewall I have exhaust coming out. I decided to do the gasket. Anyhow I got the intake and exhaust manifold off. The exhaust manifold stud closest to the radiator was finger tight, turns out someone had previously busted the stud off flush with the head; it was basically laying in there. I tried my best to work around the distributor to drill out the remaining stud but I think I am getting into the aluminum head some. I was checking myself with the new gasket as a template and using my magnet to pick up the shavings, definitely mostly steel. I actually have a heli-coil from a previous f/up that threads into the good holes in the head. I no longer have the bit. What are your thoughts on using a helicoil? I can't really drill directly into the bad hole without removing the distributor, should I take out the distributor? If I do, I have never messed with a distributor or resetting it, if I don't move anything should it go back in with no timing issues?

Also, the two middle studs, one stud came out on the other the nut backed off and the stud is still in the head. Both nuts are fubar'd, any problems with this as long as I get some new nuts? The only other stud that stayed in was the rear where the hook for pulling the engine is, all the other studs came out instead of the stud staying and the nut backing off.

[bobc]

From your description it's hard to say. Getting a broken stud out isn't that easy. You may have to take the head off and take it to a machine shop to get it out. As far as taking out the distributor, that's really simple. Just make a mark on the rotor and line that up with a mark on the case. Take out the nuts and lift out the distributor. Don't move the engine (crank) or turn the crankshaft by hand and you'll be just fine. It'll go back in the same way you took it out. Just make sure the two marks you made line up.

Good luck!

[esmit208]

Agree with BOBC

If it means that much to you, and it should, let a professional take care of extracting the studs. It sounds like you have most of the parts off that need to come off anyway. If a machine shop enlarges a hole they have the right equipment to repair the damage and cleanly retap the hole. I'm not a big fan of helicoil inserts simply because I don't have complete piece of mind about the repair. When you put the exhaust manifold back on use self locking nuts and you won't ever have that issue again. Due to vibration the one closest to the firewall is a common fail point on L6 engines at least all the Z cars I have ever had. Good Luck

[Ben's Z]

Let me throw a curve ball into all of this. If you were going to replace with the engine with a 280zxt swap within 5 months, would you still take the head off and take it to a machine shop or try the heli-coil first and just see what happens. I have a 280zxt engine that I will be putting in around May...

[FastWoman]

Ben, I have no way of telling you whether it's worth the trouble, as you'll be putting in another engine later. Getting the corroded studs out of the head can be a difficult undertaking. This may be obvious, but it's worth mentioning right here: Apply lots of penetrating oil to the studs now -- Kroil, PB Blaster, acetone/ATF mix, take your pick. Hit them again every now and then. Time and penetrating oil are your friends. Heat is another friend (see below).

As far as I'm aware, there are three ways to remove the broken-off, forward-most stud:

(1) Drill a small hole in the middle of the stud, and remove with a bolt extraction tool. That stud gets pretty corroded, so this approach probably wouldn't work. In any event, you've drilled out to the aluminum already, so it's a moot point.

(2) Weld a bolt head onto the broken stud. A skilled welder extracted a 6mm bolt from my intake manifold that way. It was snapped off about 1/8" below the surface of the manifold. He built up the welded metal with weld ontop of weld, until he had a stalk that extended high enough to weld a nut to it. I was very impressed.

(3) Drill it. You have to be VERY careful when doing this. You need enough working room to get your drill perfectly straight. You should use a punch to place a dimple perfectly in the center of the stud. Then the best way to center the hole is with pilot point drill bits. You select the size of bit that will cut out to just inside the inner diameter of the threads (not cutting any aluminum), and then you select the size of drillbit that is the same size as the pilot tip of the larger bit. Drill the smaller pilot hole into the stud as carefully as you can, and then chase it with the larger bit to remove the bulk of the material. Once that is done, drive an awl between the aluminum and steel (at the thinnest "wall" of the shell of the stud) to separate them, bending/folding the steel shell into the hole. Then work the steel out from the hole with needle-nose pliers. You'll finish by cleaning up the threads with a tap. If you're neat enough with your work, you won't need to helicoil. If not, drill larger, tap, and helicoil.

As I recall, there is not enough room around that first stud unless you remove both the distributor and the thermostat housing (which can be difficult to remove, too). Remove some coolant first, obviously, and plug the #1 ports, so that you don't get coolant in the engine. Oh, and don't worry about the distributor alignment. Just mark its position, replace the same way, and you'll be close enough to have a running engine.

If I were you, I'd replace all the studs. You can remove a "good" stud by jamming two nuts on it and using the nuts to turn the stud. If the studs are frozen in place, don't force them. Instead, apply heat with a propane torch, and hit them with a bit more penetrating oil as they're cooling. You can turn a chewed up stud with a SHARP (BRAND NEW!) pair of vice grips.

Before you install new studs, clean out the threads with a tap. Be careful of that forward-most thermostat housing hole, as it opens into the timing chain tunnel right beneath the timing chain guide. You probably won't need to chase out those threads anyway, but if you do, you'll want to remove the valve cover and watch very carefully to be sure you don't bend the guide with the tip of the tap.

Above all, take your time, and STOP whenever you get frustrated, tired, or impatient.

[Zedyone_kenobi]

Fastwoman, that was splendidly written...

And most important is the last sentence... I cannot tell you how important it is to take your time and do this correctly. Walk away and do something else if you get sore or tired. Only bad things happen when you hurry a project like this.

[FastWoman]

Thanks, Zedyone!

I forgot to mention, get some nickel antisieze to apply to the threads of the new studs and bolts. IMO, this is a MUST when screwing any variety of steel into aluminum.

[5thhorsemann]

Thanks, Zedyone!

I forgot to mention, get some nickel antisieze to apply to the threads of the new studs and bolts. IMO, this is a MUST when screwing any variety of steel into aluminum.

I must disagree with the antisieze on this one, I used that stuff on a Chebby 350 waterpump once years ago, on a long highway trip a few weeks after the waterpump bolts backed out and the pump literally fell off the motor. Given the amount of vibration in the head to manifold interface, I would reccomend the use of a tap to clear the threads and use all fresh hardware on the install, thats nuts, bolts, studs and sprung washers.

As for the removal of the stud, if you already drilled into it with the distributor in place, it's FUBAR. The only way to fix it right would be to use a mill and machine out a hole that will accept a threaded bushing. If you are going to replace the motor in the spring, just stuff a new stud in the hole loaded up with metal epoxy, let it set up and then torque the manifolds down. it will do as a temporary fix.

[Ben's Z]

Thanks everyone for the help... I am taking a lunch break now. (Actually used one of my vacation days to do this). I ended up taking off the thermostat housing and distributor out. I bought some extractors, but believe I am past the point of no return and will be going with the heli-coil. If I was not going with a different engine within the next 6 to 8 months, and less than 1000 miles I would probably take the head to the machine shop, I need new valve seals too, but that seems to be pissing away money I can use on my 280zxt engine. Looking back I should have taken out the distributor and thermostat housing before I attempted to drill out the old stud. The busted stud was actually seated deeper than the face of the head, but I still could have gotten a better angle on it. I busted a bolt off on doing the timing belt on my Tacoma timing tensioner a few years ago(in the aluminum) and used a heli coil and it has never given me any problems. I went to XL Parts here by my house (they are my customer, I am the rep for Dorman Products in Texas) and got some Dorman HELP! exhaust studs part # 03104 on the way from the other stores. Supposedly they should work according to our website, just an FYI incase anyone is ever in a pinch...

Because of my bad valve seals the tops of my intake valves have crap all over them. I found some "Guaranteed to pass emissions" snake oil in my cabinet, I poured it in the intake runners to soak the valves. Before I am done I am going to pull the spark plugs and cycle the engine to blow all that out. Does anyone see any adverse affects of using any brake cleaner to blast the tops of the valves before I put the intake back on?

[5thhorsemann]

. Does anyone see any adverse affects of using any brake cleaner to blast the tops of the valves before I put the intake back on?

Why ?

[beermanpete]

The Heli-Coil will be fine as long as it is installed correctly. Because you end up with steel threads instead of aluminum it will be better than the original threads. The main issue is locating the hole. If you get the pilot drill near enough to the true center you might be able to use a tap for the original thread size and end up with the original threads. If the pilot is off center or at an angle you will need to install the Heli-Coil.

Using solvents to clean the back side of the valves should be ok. Remove what you can before installing the manifolds. If significant amounts of solvent go into the cylinder through an open valve you should crank the engine with the plugs removed to prevent any chance of hydraulically locking the engine and bending rods. If the solvent is in the cylinder long enough it could run past the rings into the oil so you should consider changing the oil. You might want to put some oil in the cylinders since the solvent will remove the oil film. Use old plugs at start up as the solvent will likely foul the plugs.

[Zed Head]

Check out Post #6 in this thread - http://forums.hybridz.org/index.php/topic/103494-broken-studs-on-turbowhat-to-do/page__pid__969336#entry969336

If I ever need to drill out another manifold stud, I'll try to build something like it.