Broken bushing(not sure if right tern) in exhaust manifold

[BenCT]

Now that I broke this trying to take it out…not sure the next step. See photos below, last photo is what it looked like before I broke off the top of the bushing from the exhaust manifold. Worried if I cut it out with a saw that I damage threads and/or metal falls into exhaust system.

[Dave Neptune]

The coolant passage on the manifold has no access to the exhaust system within the manifold. Don't try to saw out the threads as it would be almost impossible to seal after sawing into the threads. An easy out may work if the rest of the fitting is not to tight or corroded into place. If the easy out does not work without to much trouble STOP.

If you remove the manifold which is not a big job the fitting can be drilled out and the hole tapped to the next size larger pipe thread. If you do not have the talent an automotive machine shop could do it easily without much ado.

Tapered pipe threads need to be pretty pristine as it is the taper and the threads that do the sealing.

Dave Neptune

[BenCT]

I will try the easy out. This manifold was just installed in April so it can’t be too corroded. Prior mechanic who installed it used blue plumbers dope. I used pb blaster, but didn’t seem to do the trick.

[hanleyclifford]

The same thing happened to me once on the road in the exact same place on the manifold. I was able to repair it on the anchor because I carry NPT taps with me. Get the correct drill and drill out the dead brass which should be easy because it is softer than the iron around it. Should be 1/2" NPT. When you replace the nipple use black iron which should keep it from happening again. 1/2" calls for 23/32" bit.

[BenCT]

What is everyone’s thoughts on applying heat here? Definitely not using a torch. Feel very comfortable with a small rope cutter type device but am tempted to use a heat gun. Isn’t that far from carb, but is pretty far. I’m still real timid about anything gasoline on this engine, but wondering if I’m being too cautious and could get away with heat gun here to heat the stuck brass fitting in the exhaust manifold.

[hanleyclifford]

The brass will expand more than the casting, just getting tighter.

[ndutton]

Brass is so soft a proper drill and tap should make quick work of it. I'm thinking this is causing more anxiety than necessary.

[hanleyclifford]

About the only thing worse than yellow brass in an iron casting is aluminum, and yet many of our engines have exactly that in exactly that location. The first fitting out of an iron casting should be black iron, although that is not always possible. Better choices are bronze cast fittings and red brass in that order.

[Al Schober]

Not often I get to disagree with Dave, but here goes:
Pipe threads, even if pristine, will not seal tight. As you tighten the connection, the flanks of the threads make contact and get tight while there is still a leakage path through the roots and crests of the thread form. Pipe threads need a sealant to stop leakage.
Knowing this, I would not hesitate to take a hacksaw to the broken fitting. Make two cuts close together, knock loose the piece of metal between the cuts, then collapse the rest of the fitting. If the resulting damage to the female thread is severe, just use JB Weld to install a black iron nipple.

[BenCT]

Wow, so this means instead of looking all over for these brass fittings I can just go to Home Depot and get a cast iron fitting and it’s an improvement. You don’t hear that often.

[Dave Neptune]

Al, you make a good point especially in old threads regarding sealing. However proper fresh threads are designed to seal as the materials they are made of is malleable. The JB Weld is an excellent choice for sealing gaps however quite permanent.
I highly recommend using a sealant rather that Teflon tape on engine related fittings. The tape does do a fine job but if not wrapped properly can allow bits of the tape to get into the system, especially bad in fuel systems. I like using "Leak Lock" from Highside Chemicals on any NPT fittings on an engine especially a marine engine. It comes in a blue jar or tube. It eventually "almost drys" so it has some holding power but still remains pliable for expansion and contraction due to varying temps. It also is excellent on "straight pipe threads" too. Permatex #2 and Aviation grade work well also.

NPT stands for National Pipe Tapered threads. The basic profile is a 60° truncated triangle similar to the Unified Inch threads (UNC/UNF). The main difference is that the thread profile is tapered at an angle of 1°47′ (0.75 in/ft or 62.5 mm/m) relative to the axis. The taper on NPT threads allows them to form a seal when torqued as the flanks of the external and internal threads compress against each other (no clearance remains between the crests and roots of the threads because of the taper). Depending on the application, it can be used with or without a thread sealant.

The above is from a "standards chart" for machining.

Dave Neptune

[ndutton]

Originally Posted by BenCT

Wow, so this means instead of looking all over for these brass fittings I can just go to Home Depot and get a cast iron fitting and it’s an improvement. You don’t hear that often.

You might consider following Moyer Marine's lead on this by examining their rebuilt engine practice. A 360° view is found here. You'll see many of the parts threaded into the block, head and manifold are of metals other than iron or steel, plumbing parts and gauge senders are examples.

That said, there is no escaping that pure brass is soft. If you are looking for a rust-proof fitting with better strength, bronze is a better choice. McMaster-Carr offers plumbing fittings in iron, steel, stainless steel, brass and bronze (that is, everything you can imagine) and delivers to your doorstep.

[hanleyclifford]

Originally Posted by ndutton

You might consider following Moyer Marine's lead on this by examining their rebuilt engine practice. A 360° view is found here. You'll see many of the parts threaded into the block, head and manifold are of metals other than iron or steel, plumbing parts and gauge senders are examples.

That said, there is no escaping that pure brass is soft. If you are looking for a rust-proof fitting with better strength, bronze is a better choice. McMaster-Carr offers plumbing fittings in iron, steel, stainless steel, brass and bronze (that is, everything you can imagine) and delivers to your doorstep.

Yup - lots of yellow brass on that 360 view. Looks great when it's new.

[msmith10]

You could also try an internal pipe wrench.

[hanleyclifford]

Originally Posted by msmith10

You could also try an internal pipe wrench.

That might actually work. Put a little Kroil in there first.

[sastanley]

This all seems to be well in hand, but I will comment from Dave's earlier..there are only 3 studs holding the manifold to the block...once you move all the other junk out of the way.

[BenCT]

Threads are cleaned up. In the end it was a combination of drilling, pulling out some of the destroyed bushing with a needle nose plier and then tapping the thread. Having said all that, don’t know if it leaks yet.

[BenCT]

The big problem was I over tightened the brass fitting and the threads were all fused together. The easy out, internal pipe wrench and everything I tried to back out the bushing (after using PB blaster) just ripped up the soft metal. It’s a lesson in not overtightening those types of fixtures.

[hanleyclifford]

Originally Posted by BenCT

The big problem was I over tightened the brass fitting and the threads were all fused together. The easy out, internal pipe wrench and everything I tried to back out the bushing (after using PB blaster) just ripped up the soft metal. It’s a lesson in not overtightening those types of fixtures.

But did you rip up the casting? If not, you can proceed to retap. If yes, you can go up to 3/4" NPT.