Installation of the "Big Neck"
C. J. Frederick
We all want to increase the performance of our cars. The simplest modifications are usually the most successful for the apprentice home tuner as a high level of technical and tuning expertise is not required to realize gains. Big exhausts and free flowing air cleaners are examples of basic modifications that realize immediate improvements. Enter the Duttweiler Neck. This modification appears to be a straightforward process of wacking off the stock restrictive intercooler (IC) intake neck and welding on another that has a much larger internal diameter.

The Duttweiller Neck is an aluminum casting that can be purchase from some of our suppliers. See the venders list on the Turbo Regal homepage. I ordered mine from Kirban Performance Products and it cost about 75 bucks including shipping. It comes in a kit that includes the neck casting, a special stepped connecting hose and two stainless steel clamps.

This modification was a natural for me as I have over 35 years of welding experience and a TIG welder in my garage but any competent welding shop should be able to do the modification. To obtain the best results (air flow) the neck to IC weld joint must aligned internally. Just welding it on will show flow gains but for maximum improvement the installation requires a little extra care. More on that later. Some of the tools I used are shown in the picture . Not shown are a hacksaw, electric Milwaukee saw, 7 inch air grinder and of course the TIG welder. Not all the small tools are totally necessary but it speeds up the installation.

The famous "neck" ready to be installed...
Tools used ...
You Will Need
First clean the inside of your IC. During the installation of the new neck a lot of grinding and sawing metal dust will get into the IC. These small particles will stick to the oil residue usually found inside the IC and be difficult to remove later. If not removed, after the installation these aluminum particles will end up inside your engine. By getting the inside of the IC clean before the neck is installed, it will be easier to blow and flush out the metal particles before you put it back on your car.
Prepare the New Neck
Sharp lip to be filed down...
The Duttweiler neck arrives as a rough casting. It has normal casting debris inside that will obstruct flow. This debris should be removed and the inside smoothed. I used a carbide cutter to remove the heavy casting flash and a sanding roll to smooth and blend the inside surfaces. A flap wheel does a nice job of putting a satin finish inside but this is optional. There was also a sharp lip on the inside of the neck opening that I removed with a file. The edge was also squared up with a file. Having this surface flat makes sure the weld joint doesn't have gaps later. These may be minor flow restrictions but the little things can add up. Some of the casting debris was gritty and could flake off later and get in your engine
Cutting the Intercooler
Using the level to determine cut lines...
The toughest part of the installation was to determine where to cut the stock IC neck. The stock neck casting is round, tapered and at compound angles to the IC. It is difficult to mark an accurate cut line on the IC neck when it is on the car as the stock neck is in the way for fitting the new neck.

Plan B, I used the location of the old neck opening to determine the position for the opening of the new one. I traced the OD of the Duttweiler Neck on a piece of stiff paper, cut it out and traced the OD of the opening of the stock neck inside the circle of the Duttweiler circle. I then clamped the IC to my bench and checked the angle of the stock neck.

By positioning the Duttweiler Neck over the stock one, aligning it with a square to the tracing and setting it to the angle of the stock neck, the cut lines could be determined. The picture should clarify.

Note, I used a digital level. The plastic ones only cost about 10 bucks and will work but I hate the bouncing needle. To make sure the alignment was correct I cut the IC neck off a half inch short for the first trial fit. There is probably a better way but this method worked for me. I cut the neck off with a power hack saw and dressed the cut surface flat (for a more accurate trial fit up)

Final Fit Up
Neck taped in place wth scribe line and center punch marks...
After the first cut, the IC was installed and the new neck put in position for the first trial fit. The IC stub was wrapped with masking tape. The new neck was adjusted to line up with the turbo outlet. The final cut lines were marked on the tape. The IC was removed and the second cut was made. The IC and the new neck were retaped and the IC installed again.

After the neck was again aligned with the turbo it was taped into position. The IC with the new neck taped on was removed. Three lines about 3 inches long were made through the weld joint. Two points were made on the lines 2 inches apart, one on each side of the weld joint.

The lines were scribed into the neck and IC and the points center punched. These lines will be used for final tacking alignment prior to welding

Fixing Internal Misalignment
You can see the mismatch between the
intercooler and the neck clearly here...
All the tape was removed as it makes a real mess if the adhesive gets hot from the weld heat. A template was made of the ID of the Duttweiler Neck. This was done to insure the flow path to the IC was smooth with no obstructions. After placing the template over the opening on the IC it became obvious that there was a problem. The opening to the IC had two sides that didn't line up with the new neck. See the photo.

This is serious because the flow from the neck would "catch" the edge of the IC. To correct the misalignment, two pie cuts were made into the opening edge of the neck. The sides of the IC opening could then be bent out to align the opening to the new neck.

The cuts will be filled with weld later.

Weld Prep
A close up of the beveled joint on the new neck ...
To insure sound welds all joints are beveled with about a 1/16 inch land. The pie cuts must also be beveled. The beveling will allow for full penetration welds necessary for strength. I used a 7" grinder with a 36 grit pad to bevel the weld joints.

To make sure the pad doesn't load, the pad was turned fairly slow to keep the aluminum from overheating. The beveled weld joints in the IC opening can be seen in this photo. The photo shows a groove cut between the ends of the two pie cuts. This is where the IC cracked when bent out for alignment. The crack was completely ground out for repair. The new neck must also have all the weld joints beveled.

Welding up the cuts ...
The pie cuts were welded first. The ends of the pie cuts were tacked at the opening to make sure they didn't close up from weld shrinkage. Two passes were used to insure 100% penetration. The first pass was purposely melted through to the inside of the IC. The weld that melted through was ground off later before the new neck was welded on.

The next problem was to make sure the neck is aligned with the turbo outlet and the ID of the IC and the neck are aligned. To make sure the new neck was positioned correctly, the scribe lines were aligned and the punch marks checked to make sure they were two inches apart. When in position the neck was tacked in place with two cold tacks. The ID alignment was checked with a small mirror.

The alignment was off so one tack was cut and the neck shifted into alignment on that side and retacked. Then the other tack was cut and it was realigned and tacked again. The process was repeated to "walk" the neck into position. Once the ID surfaces were in alignment a deep, hot tack was made on all sides. This photo shows two cold tacks that were cut and a hot tack in the middle. The cold tacks that were cut were ground off before final welding.

The neck was then ready for finish welding.

The finished product ...
After tacked up securely, the neck was welded on with two passes. The penetration of the first pass was carefully controlled so no weld melted through to the inside of the neck and created an obstruction to flow.

If this occurred there would be no way to grind it out with the neck installed. The final pass finished the job.

All that is left is to decide wether to leave the welds and the word Duttweiler on or grind them off to make the installation covert. The completed IC should be scuffed up and painted and then (important) blown out with air and flushed with hot water to insure no metal debris remains inside.


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