I would like to install a EGT gauge/probe. I'm guessing after turbo is the easiest and cheapest way to go (although not as accurate). Is there enough meat on the down pipe to thread it or does it require a nut to be tack welded on?
Thanks.

my

 

Drilling and tapping the exhaust manifold is probably the easiest and most accurate way to go. If you plan on drilling the downpipe, some companies make a hose clamp that goes around the downpipe and you snug the pyro in there with an asbestos washer to help "seal" the hole you make.

 

Thanks,
I assume to drill and tap the manifold one would have to drop the turbo to keep shavings from being ingested through it or is there a "trick" to doing it with turbo in place?

 

I've done three with the turbo in place and no problems. I did however take my time and use grease on the bits (drill and tap) to catch the shavings. Also when I got close to getting through the manifold I started the truck then finished the hole, this "pressurized" the exhaust and blew out any shaving out the grease didn't pick up. Also there is a divider in the middle of the manifold downtube so most people drill and tap the back downtube, supposedly pistons 5 and 6 are supposed to create the hottest exhaust.

 

I'm getting ready to do this job in the next week or so. Like you, I prefer to do my home work before starting the job. This is what I learned:

1. Pre or post turbo is a matter of choice. Post turbo temps will be lower.

2. Post turbo is easier to install and safer for the turbo. Although hundreds (thousands?) of people install pre-turbo without any problems at all.

3. There's not enough meat in the down pipe to support the fitting and thermocouple. You need to add a T clamp that has a hole in it for the thermocouple leads to fit through. It will then clamp over the thermocouple and support the whole thing.

4. If you drill through the side of the manifold, start with a very small bit, and gradually work your way up to the correct size. Use low pressure and high speed on the bit. Make sure the bit is very sharp. This technique will produce more "dust" and fewer big chips.

5. Drill bits are designed to pull material out of the holes they drill. If the flutes are packed with grease, it can't do that. So make sure you clean and regrease the flutes often. Apply some grease, but don't pack it in.

6. Taps are differant. Material and chips go with gravity. Greasing and frequent cleaning are the order of the day.

7. Make sure the thermocouple leads are tied up out of the way. They can be burned despite the braided covering.

 

Thanks for all the advice.

 

You can "drop the turbo" 1/2" by just unbolting the mounting flange, enough to slide a piece of cardboard in there to cover the inlet. You may or may not need to loosen the intake and exhaust to get enough wiggle room. Drill and tap to your heart's desire, no worries about bit sizes, speed, grease or anything else. Then start the engine for just a few seconds to blow any debris from the manifold out on to the floor. Replace gasket, re-assemble, done.