Boost/EGT guages install

[arveetek]

I'm finally getting around to installing my Isspro gauges that I purchased from JK nearly two years ago (for the Tahoe). I got the A-Pillar pod painted and installed, the gauges installed, and the wires run. Now I just need to physically hook up the boost line and EGT probe.

I've been searching for where folks have been installing the boost tap. On my '81, I drilled and tapped the upper intake plenum I made. Is this the best bet? Do I need a new upper intake gasket if I take the upper plenum off? Is it safe to drill and tap the plenum without removing it if I'm careful not to let any bits of metal fall into the intake? I've also read where some have tapped in the existing sensors with a tee. That sounds pretty good too. What say ya'll?

On the EGT probe, I figured I'd follow JK's advice on his website and drill and tap the exhaust manifold right below the turbo inlet. Any advice or tips?

Thanks!

Casey

[Robyn]

The air hat comes off real easy. Drill and tap the back side of the snout just downstream from the turbo connector hose. Do it on the back side.
Do this in 1/8th pipe thread.

Now the exhaust can be a bit touchy. If you are going to drill the manifold, I would not !!

Drop the crossover pipe and drill a nice hole in it and weld in a Bunge that has the proper size thread for your sensor. Be sure there is no crap left in the pipe that can fly on up and go through the turbine. If anything hard goes through those fins at warp speed its game over.

The hole in the pipe can be on the back side just below the outlet from the manifold. (LH SIDE)
This will give you good accurate temps and is the easiest to do. Mark the spot before you drop the pipe so you can be sure there wont be any interference with anything under there.

You can easily route your wiring up and into the cab from this point (Or down from the cab :D )

Since your placing your gauges in the pillar this will give you more usable cable to work with. The should be a suitable spot to get through the firewall right close there.

Drilling the manifold is sweet if the manifold and turbo is off the truck so you can clean it out good.
I personally would not fight that stuff off of there just to place the sensor. The inlet to the crossover will do fine.

Now,if you cant find a "weld Bung" you can use a piece of 3/8" X 1X1 bar andhot form it to the pipe and weld it on then drill and tap it to suit.
Just many ways to do this depending on what you have to work with.

The main thing is to NOT introduce any Missles into the exhaust system that will fly through your turbo

Good luck with the project

Robyn :)

[rustyk]

The EGT probe can be safely done on the engine, with it running; the exhaust prssure will blow any chips out.

I removed the intake manifold/plenum on mine when I drilled and tapped for the boost gage; IMHO, there's no way to safely do it unless off the engine. Even if the intake manifold gasket is intact when you remove the manifold, it probably already has a "set"; it should either be replaced, or a thin coating of blue RTV gasket compound applied.

[sturgeon-phish]

Do a search using "A-Pillar Gage mount for EGT, Boost and Transmission Temp." and I have pictures and a step by step instal instructions on page 2 of the thread.
Jim

[trbankii]

I recently came across references to a "boost bolt" that you pull a bolt out and replace this to provide a tap in point for a boost gage. So far, it seems like it might be a CTD-only thing and the places that sell them don't have a whole lot of information. Anyone know if one can be used on the 6.5?

[JohnC]

The front most and rear most bolts holding the upper manifold to the lower go all the way through into the manifold (IIRC). GM has a hollow bolt for just that purpose. Dr Lee drilled a bolt for that application. I apparently don't have the necessary skill level (or patience...).

[trbankii]

Any idea on the GM part number? Although, it wouldn't be much work for me to drill and tap a bolt...

[edit]Finally found some pictures of the CTD setups and they seem to be using a banjo bolt. Maybe a suitably sized one could be found?

[arveetek]

I installed the boost tap last night. I removed the upper intake plenum and then drilled and tapped it for the boost line. Was actually pretty quick and easy. I'd say it would be much easier to do it this way than trying to drill and tap a bolt. If you could find a bolt already modified, then that would be a good way to go.

I'm quite fascinated by the way the wastegated turbo on the 6.5L behaves as compared to the non-wastegated turbo on my 6.2L. The 6.5L builds turbo very quickly and then holds a steady 7 psi throughout the rpm range, and actually begins to drop off at higher rpm. No matter what speed, gear selection, or rpm range, you can pretty much count on 7 psi.

My 6.2L also builds boost very quickly but continues to climb all the way up the rpm range. The more fuel you feed it, and the higher the rpm, the higher the boost, until it tops out at around 18 psi at near the max. rpm. So boost directly corresponds to fuel feed and rpm. If you hold the fuel steady but drop down into a lower gear, the boost will jump up in response. Not so on the 6.5L. Very interesting.

I can see how GM thought that having a constant boost pressure would be beneficial and also not too agressive on the engine. However, I can also see how towing heavy loads with a stock 6.5L could result in engine damage as the boost will drop off and the EGT's rise at higher rpms.

I still need to install the EGT probe. I'm thinking of removing the right front wheel, and then drilling and tapping the manifold through the available opening. I'd rather put the probe in the manifold, since I have a performance exhaust sitting in the garage ready to be installed. I want to get real before and after data, so that would be the best place for the probe.

Casey

[JohnC]

Any idea on the GM part number?


No.

I think it's a "Special Tool." If anyone has the service manual, it's probably listed there.

[john8662]

Casey,

It's about time ;)

I like the installation with the hose clamp on the driver's side x-over pipe, the clamp-on thermocouple.

Which TC do you have?

If you have the drill n tap version, you'll probably have to remove the inner fender on the pass side to get at the raised portion on the manifold.

On mine, the size was 1/4" NPT verses 1/8" NPT, because the probe screwed into an adapter (because it was adjustable for the depth.

Kind of a pain to drill n tap in that location, plus you gotta drill with the thing running to blow out the shavings. You can tap without it running just by using some oil/grease on the tap and taking it slow, pulling it out and cleaning it off (that sounds bad, I know), and then putting it back in to get good clean threads...

Exhaust system? Does that included the x-over pipe?


Others,

Special Tool is a Kent-Moore tool, used for temporary testing for boost pressure, especially handy on 92-93 trucks that have no MAP sensor (ECM) to measure boost pressure. I have one, they're not really cheap, and I don't really know how available they are...

[arveetek]

Casey,

It's about time ;)

Which TC do you have?

On mine, the size was 1/4" NPT verses 1/8" NPT, because the probe screwed into an adapter (because it was adjustable for the depth.

Exhaust system? Does that included the x-over pipe?



Yeah I know!!! I've been busy, K? :D

I have the same TC as you, with the 1/4" NPT threads. That's gonna be a bit harder to install, I know.

The exhaust system will include a new crossover and downpipe. I haven't got them yet, but I'll probably go with the kit from Summit Racing. It's cheap and should be enough for my Tahoe with a 3.5" exhaust.

Casey

[sturgeon-phish]

Since you are going with a new crossover pipe, may I suggest welding the 1/4 bung in the crossover on the drivers side for the EGT. That is where I have my tap and it works very well.
http://i126.photobucket.com/albums/p81/sturgeon-phish/Truck/000_0003-6.jpg
Jim

[arveetek]

Since you are going with a new crossover pipe, may I suggest welding the 1/4 bung in the crossover on the drivers side for the EGT. That is where I have my tap and it works very well.
Jim

Thanks for the suggestion, but I want to get readings before I install the new crossover pipe, so I can see what changes, if any, are made by the new exhaust system. Hence, my desire to install the probe in the manifold.

Casey