Help request: tapping exhaust manifold

[Matz]

So I've got to get my EGT sensor installed this week. I'm going to tap the #1 runner, and have a couple of questions:

1. I've read that you should let the engine idle when tapping to help blow out the chips. However, wouldn't suctioning the chips out while drilling be better? If you're going to blow the chips out with the engine running, why would that be any different than doing it with the engine off, and letting them blow out after? Do we have to worry about chips going into the turbo, or getting stuck in the cat's honeycomb?

2. What's the best sealant? I've heard Loctite is good, but which one? I've also been told that over time, the Loctite dries up and becomes less effective, so a different sealant is better. However, I don't really know myself. This is just second hand information. I'd love to get your guys' opinions on this.

Thanks!

[EVO GRIM]

Drill slowly and use oil. Clean off the fillings as you go. Running the engine is just so the last little filling blows out instead of going in the exaust system. I dont know about sealant, however npt I believe gets smaller the more you go in so dont over tap. Its like plumbing threads not like a bolt thread. So the more you turn the tighter the threads become. I just got my defi gauge, I'll be right behind you. So let me know how it goes.

[Matz]

Cool Marshall, thanks. I will definitely use a generous amount of oil to get the chips to stick. However, I will also run the shop vac at the same time. You're right about NPT, but it gets wider the farther in you screw it (I know you meant that though). The point of NPT is to allow a seal because of the taper, but I still think it's a good idea to use some kind of sealant. I'll video the tapping job and post up here for everyone once I'm done. Hopefully, I won't f**k up or it'll be one more thing for people to laugh at. :lol:

[MarkSAE]

No sealant will survive the temperatures seen at the exhaust manifold. The best thing to do is do a good job tapping the hole by not going too deep. It shouldn't leak w/ the tapered NPT threads.

I'll be drilling and tapping my exhaust manifold tonight w/ the manifold out of the car though. If I were gonna drill and tap the exhaust manifold on the car, I'd drop the cat so all the shavings can exit the car. Otherwise, they'll get trapped at the cat. I don't see how whether you do it w/ the engine running or not will make a difference either.

[Matz]

No sealant will survive the temperatures seen at the exhaust manifold. The best thing to do is do a good job tapping the hole by not going too deep. It shouldn't leak w/ the tapered NPT threads.

I'll be drilling and tapping my exhaust manifold tonight w/ the manifold out of the car though. If I were gonna drill and tap the exhaust manifold on the car, I'd drop the cat so all the shavings can exit the car. Otherwise, they'll get trapped at the cat. I don't see how whether you do it w/ the engine running or not will make a difference either.

Ok, thanks. I'd drop the cat from the car, but it was such a PITA to get it off when I did the exhaust swap last time that I don't want to deal with it again. :) I'll be as careful as possible.

The only thing I wonder about is when the temps get really high -- will there be enough expansion in the manifold to cause a leak around the threads?

[DRFTR8]

I don't see how whether you do it w/ the engine running or not will make a difference either.

if you run the car the shaving will head down to the turbo.. dont run the car.. when your tapping the manifold, drill the hole and use a stick with a magnet on the end of it so you can collect the shavings that are stuck inside.. then when your using the threading tool, i would use shaving cream around the tap so it will collect the shavings so you can just wipe it off when your done, again use the magnet to collect the shavings inside.

Note: i saw that last sunday on Horsepower TV, when they needed to tap the manifold on the grand national they were building :D

[Matz]

if you run the car the shaving will head down to the turbo.. dont run the car.. when your tapping the manifold, drill the hole and use a stick with a magnet on the end of it so you can collect the shavings that are stuck inside.. then when your using the threading tool, i would use shaving cream around the tap so it will collect the shavings so you can just wipe it off when your done, again use the magnet to collect the shavings inside.

Note: i saw that last sunday on Horsepower TV, when they needed to tap the manifold on the grand national they were building :D

Thanks!!! Wow, a magnet. I can't believe I didn't even think of that. :) I think tapping oil should be good enough to get the chips to stick, though.

[earlyapex]

I've done about 15 EGT installs in my life and every single one I have had the car running, with the manifold on the car, oiling the drill bit while doing it and have not had one problem whatsoever. I've done it on catted and uncatted cars.

Running the car blows the chips out of the manifold. Oil keeps the bit from heating up too much and stops the rest of the chips from going into the turbo.

Like everyone said above, don't tap too deep. Taps actually go from small to large, so if you tap too deep the probe fitting won't thread securaly.

I've never used sealant of any kind on the probe fitting, anything you use would burn off in no time. Just make sure it's tight and you're good to go.

The job really is easier than you think it is. Everyone can talk about what method should in theory work better but until you do it a bunch, you realize what works and what doesn't in the real world.

[Matz]

okie dokie. I plan to tap a little at a time and thread the bung in after each attempt, until I can get it flush and tight with the manifol. This is gonna be fun! I can't wait... and if I screw up, then that's a good excuse to buy a new manifold and get it tapped and ceramic coated ahead of time. :) I'm really not that worried. I've drilled and taps tons of different stuff and various materials, so the manifold should be cake. It's just that NPT tapping is new to me, and the fact that it's on a car is scary...hehe

Ah, damn, one last question -- what size drill do you use for 1/8" NPT?

[earlyapex]

Remember not to let the probe touch the actual manifold bottom wall. You want it to basically be hanging there. Therefore, you should thread in the probe bung accordingly. It doesn't have to use all the threads, just enough that it's tight, which again, stresses the importance of not tapping too deep.

I should take a photo of mine at some point...

[earlyapex]

Matz:

From RRE:

GReddy 52mm Electronic EGT Gauge Instructions
http://www.roadraceengineering.com/instructions/greddygaugeinstructions.htm

Sensor Install

1. Cylinder number one runs the hottest so we put the sensor in the
runner for number one. Drill the manifold with the motor running;
this will blow out the chips. You do still need to respect the danger
in the possibility of metal chips getting into the turbo. Drill slowly,
especially when you are about to break thru. The entire time you
are drilling and tapping the motor needs to be running.

The only time we had a problem was when we forced a stuck tap,
the tip broke off. If a large enough piece goes down in, you will hear a
"dinging" noise from it hitting the turbine wheel. You will have to
take off the turbo to get it out, it will NOT blow out. If you are careful
and don't rush things, you wont have a problem.

The probe goes about 1/2 way between the cylinder head and the
collector area. There is a flat spot on the heat shield that works well.
Drill a 1/4” starter hole through the heat shield and down to and just
mark the number one runner. Next take off the heat shield,
start the engine and drill a 21/64" hole in the manifold. With the motor
still running, tap the hole for the GReddy temp sensor fitting (1/8" NPT).
If the tap hangs up at all, don't force it. Back out 1/2 turn and go in
some more. Don’t tap too deep, the sensor threads are short. You can
turn off the motor now.

Screw the fitting (the one threaded on both sides, screw in the longer side)
in first. Use a little anti-seize on the threads if possible. Next slide the
open ended nut onto the sensor and then slide the sealing washer onto
the sensor. Slide the sensor into the fitting already screwed into the
manifold and tighten it down with a 12 mm wrench. Cut a larger hole
in the heat shield for the manifold. The hole should be about 1" diameter.
When you install the heat shield, be careful to not kink the wire coming
out of the sensor.

2. Run the wire from the sensor through the firewall. You can poke it through
boot for the steering column. Use an Exacto knife and cut an X-shaped
slot through the rubber. Push the hose through this hole. Be careful routing
the hose under the dash so as not to interfere with the movement of the
pedals or steering column.

[Matz]

Hey Bryan, thank you very much for posting that info. I'm sure it'll be extremely helpful. And thanks for pointing that out about that sensor / bung depth!

[SouthernCrane]

If your motor wasn't running while tapping, what could happen to the turbo if the shavings go through it anyway? and how would you know if there was damage to the turbo?

[MarkSAE]

If your motor wasn't running while tapping, what could happen to the turbo if the shavings go through it anyway? and how would you know if there was damage to the turbo?

I guess in the worst case, the metal shavings from your exhaust manifold can fall into your turbine house and then get wedged between the turbine wheel and the center cartridge, then it'll work it's way into the seals. This is highly unlikely though. With your car running, the exhaust gases will push the shavings through the turbo quickly.