This is not a complete instruction on how to install gauges. However a common question we get here at DK Diesel is where to drill and tap for a pyrometer probe installation. Here we will try to explain the easiest, and safest methods for accomplishing this install.
The exhaust manifold is a dual passage design with 3 cylinders feeding into a front and rear exhaust runner with a vertical wall separating the two runners. Thus, the mounting hole cannot be drilled down the center of the manifold. It must be drilled in the center of either the front or rear exhaust runner. PDR recommends using the rear exhaust runner in most cases.
Locate a point two inches from the turbo mounting flange in the top center of the exhaust manifold. Using a center punch, measure 5/8 of an inch forward or rearward of the center of your manifold. Mark your location. With a small drill bit, 1/8" or smaller, drill a pilot hole. This helps insure the bit stays centered, and your hole stays circular. The last thing you want is to weld your manifold and start over. Once your pilot hole is drilled, you need to figure out the size of your NPT fitting. If you have an 1/8" NPT fitting, use a 11/32" drill bit, and finish drilling your probe hole. If you've got a 1/4" NPT fitting, you'll need a 7/16" bit. Take your time, and make sure you're using the correct size. Again, if your friends find out you had to weld your manifold during an EGT probe install, they'll never let it go. Ever.
Using the correct tapered tap for your probe size, carefully tap the hole. The keys to this step is keeping your tap straight and level, using consistent pressure, and not using too much force. We recommend using a 3/8" rachet with a short extension to give extra leverage and control.
An important part of the process will be removing all of the drill and tap shavings from within the manifold. There are a number of ways to do this. The most effective, but also the most time consuming way is to remove the turbo for easy access into the inside of the manifold. Other tricks to remove shavings without removing the turbo include putting Vaseline on the drill bit so the shavings stick to it, using a small rubber hose with a make-shift attachment to a shop vac and sucking them out, and using a small mechanics magnet that fits down the hole, and repeatedly removing shavings until the magnet comes out clean. Use as many tricks as you can. Once against, be thorough and patient. Turbo's and metal shavings DO NOT get along.
Finally, study the pictures below before starting to verify you have marked the correct location to drill and proper depth to tap for the pipe fittings. These are very important.
When all is said and done, you should have a working, exhaust leak free, EGT probe installed.
Have questions or comments? Let us know!
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