Drilling and tapping exhaust manifold

[Jetpilot]

For one, the exhaust has pulses, so the chips can be sucked in, as well as blown out. They can even be sucked up into the cylinder, then spit back out. When you drill a hole into the side of a pipe carrying a fluid at high speed, it may also cause a suction at the hole due to a venturi effect. It varies with where you drill it. I still think the safest is to have the motor off, then use a magnet inside the hole, until there are no more chips coming out.

The venturi effect is where there is an increase in velocity there will be a decrease in pressure. But when you have a pressurized manifold (which this is) the pressure is greater on the inside thus any hole will cause the pressure to move from high to low. The gasses in the manifold are contained and thus the venturi effect does not apply. Now as the gasses escape the manifold the pressure around the escaping gasses will create a low pressure area outside the manifold. As for the pulese, if you have negative pressure created by an exhaust port there is something very wrong with the engine. The pulses are actually pulsing pressure differentials due to the compressed gasses escaping into the manifold from the cylinders when the exhaust valves open, no negative or way to be sucked back in.

 

[betterthanstock]

The venturi effect is where there is an increase in velocity there will be a decrease in pressure. But when you have a pressurized manifold (which this is) the pressure is greater on the inside thus any hole will cause the pressure to move from high to low. The gasses in the manifold are contained and thus the venturi effect does not apply.

The venturi can be the drill bit itself falling into the manifold (and creating a local narrowing of the cross section), with cast iron chips flying from its tip, or the tap, again surrounded by chips, that will all get swept right into the turbo by the fast moving air.

Now, if you were drilling into a high pressure vessel of stationary air, maybe most of the chips would be blown out, but even then some will fall in as the tap pushes them right in.

 

[jmblocker]

Personally I look at that turbo as a small jet engine. Just thinking about the chance of metal shavings or a single metal shaving moving through something that is turning at such a high RPM kept me from going pre-turbo. If you even get a small nick on one of the blades the turbo will slowly start to FOD itself out. And over time (shorter than normal) it will it will fail. The purpose of the temp gage it so you can have a relatively good idea as to what your turbo temp is, post or pre; same thing just a different reading scale.

Ten people ten different reason; mine safety and $$



Mike

Can you tell me about what the normal temp gauge readings (EGT"s) are in the Post turbo install?? I'm thinking of doing this project too...

Thx, John

 

[Bob4x4]

Post turbo is very slow to respond. I can see 600 degree diff when hitting a grade. I want to know what is hapenning as it happens not after it already has :-laf



Bob

 

[Buffalo]

Many of the folks that are posting on this thread are far more savvy at "wrenching", than I am but, I will post what I did.



I loosened the bolts that hold the turbo to the manifold so that a small space was created between both pieces. From a cardboard cereal box, I cut a piece that would fit in the space between turbo & manifold. Drilled & tapped the manifold just above where the turbo connects. With compressed air, I blew out the drilled hole & then blew the debris off the top of the cardboard piece. Installed the pyro probe, removed the cardboard piece & re-tightened the turbo bolts.



I realize this was probably "over-kill" & a bit more work but, it worked & I had no worries about getting metal shavings into the turbo.



The credit for this idea shouldn't go to me since I "stole it" from another member, on this site.



Joe F. (Buffalo)

 

[betterthanstock]

Buffalo, your method works, as long as you drill in the vertical (lower) portion of the manifold. Otherwise, when you blow with air, it may send some chips back into the engine.

 

[WMoroni]

Seems everybody worries about this way to much. Not that big a deal. Shut the engine off and let it cool so that you don't burn yourself, because that's about the only thing you could hurt with this mod. Bigger and harder flakes of rust and carbon go through the turbo on start up after the truck has sat a few days than ever could metal shavings from drilling a 1/8" hole in the manifold.

 

[MasterChief]

After much research what I have found is don't blow past 1200 if you can help it. 1000 dges is ok as a max working temp such as pulling a long hill.

 

[bsappington]

I would like to say that I understand everyones concern. I have done this to several trucks now with no problems. One very clever member of this site set me straight. If you hhave an exhaust brake, when the engine is cold start it, turn on the brake and drill. Do the same proceedure for the tap only wear gloves. The tap gets hot quick. You have to be quick. Also I highly recomend eye protection.



If you don't have an exhaust brake just place a coffee can over your exhaust pipe. That will solve the problem of sucking anything into the exhaust.



As for post turbo, I can tell you that in my opinoin it is a waste of time. Any reading you get from this area is useless even if you are trying to calculate the temp. diff. over the turbo. I thought I could and I was not even close. Just take the plunge and drill the manifold. I put it off for years on my 99 and when I finally did it I could not believe how far off I was. I drilled my 04 before I had even made a payment.

 

[rbattelle]

As for post turbo, I can tell you that in my opinoin it is a waste of time. Any reading you get from this area is useless

I respectfully disagree.



I've always said - probe location depends on why you want the probe.



If you want to monitor turbo temperature for shutdown, post-turbo is the way to go. A pre-turbo EGT will not necessarily protect the turbo during shutdown.



If you want to prevent melting down the engine (particularly when performance boxes are in use), pre-turbo is appropriate.



My engine is bone stock, and my thermocouple is in the turbine exit pipe. Some day I will have one in the exhaust manifold too - to watch for a failed injector.



Both locations are useful.



Ryan

 

[JHardwick]

I can't believe people are still stressing over this how many years later?

I drilled and tapped the hole, installed the probe and fired it up!

The shavings were blown through the turbo before it spooled up ... ... ... ... ... this was 370,000 miles ago!

 

[bsappington]

I respectfully disagree.



I've always said - probe location depends on why you want the probe.



If you want to monitor turbo temperature for shutdown, post-turbo is the way to go. A pre-turbo EGT will not necessarily protect the turbo during shutdown.



If you want to prevent melting down the engine (particularly when performance boxes are in use), pre-turbo is appropriate.



My engine is bone stock, and my thermocouple is in the turbine exit pipe. Some day I will have one in the exhaust manifold too - to watch for a failed injector.



Both locations are useful.





In that respect I agree.



I guess what I should be saying is that I find pre turbo to be far more useful that post turbo. If your pre turbo temp is below 350* for a short amount of time then I believe you are safe to shut your engine down without baking the oil in the bearing. For many people that are installing gauges I believe the biggest concern would be protecting the engine. Having the EGT's in both places on my 99 I certainly would pick putting the RTD in the manifold.



Besides a turbo is much cheaper than an engine.



Also I believe that if you are monitoring exhaust temps for mileage then you will get much better information pre turbo.



Just my $0. 02



However the biggest thing I was trying to say is don't be affraid to drill the manifold. Everything is scary the first time. Just take your time and becareful. Nothing is worth getting hurt.



Ben

 

[RodMorris]

I just installed a Westach dual boost/EGT gauge over Christmas. Drilled and tapped the manifold, used a magnet to make sure all the big shavings were out, and didn't have a bit of problem.



It's interesting watching the EGT - I would never have thought it would change so much and so quickly.

 

[BHolm]

After much research what I have found is don't blow past 1200 if you can help it. 1000 dges is ok as a max working temp such as pulling a long hill.

See, that is the problem, the pre-turbo numbers are the engine damaging ones. My stock 06 could easily hit 1100 post turbo empty climbing a hill. For an 06 those numbers, even post turbo are not quite right IMO. Pre-turbo 1450 sustained has been bantered around as safe according to Cummins on the "600" trucks. The newer engines have more safegaurds to allow the higher temps.

 

[JMichelson]

Ok, I'm convinced. Anybody have a picture of the location to drill. I'm going with the Westech dual gauge on the piller. Thanks for all the information.

Jeff

 

[ERobinette]

Hi all, I just moved mine from post turbo to pre turbo. The engine runing idea sounds great except if I had done it I would be buying a new turbo today. When the drill bit went through I lost my balance and broke off the drill bit. Now I have half a drill bit in the exhaust manifold- not good. I pulled the turbo and removed it.

 

[Grey Wolf]

Well a good mechanic is one that can fix his mistakes

 

[Bob4x4]

Well a good mechanic is one that can fix his mistakes

:-laf I like that... ... . you always see the bright side.



Bob

 

[ERobinette]

Grey Wolf thanks for the compliment. I thought I would be taking a bit of heat for my ballet dance.

 

[Scooby]

Grey Wolf thanks for the compliment. I thought I would be taking a bit of heat for my ballet dance.

It all depends on how you ended it..... Did you graciously raise your arms and exclaim "ta-da!" at the end... . or did you curse and scream?:-laf It's all in the presentation.