Modifications - Page 1

I don't really plan to do many modifications to the car, but I do want to improve it and personalize it just a little. I won't do anything that cannot be easily reversed.

I plan to reinstall the optional 18-inch wheels which came with the car when it comes time to put new tires on it. At the rate I'm driving it, it will probably be a while before that need arises however.

One modification which is kind of an on-going item is a custom tune. Since I like to do things for myself and start small and work up to more complex things and since I'm keeping the car basically stock, I decided to go with a DiabloSport Predator hand-held tuner. Last Summer I experimented with the two kinds of canned tunes available in the machine. Both tunes really made a noticable difference for the better in both power and fuel mileage. Through on-line contacts I learned how to analyze and adjust the long term fuel trims (LTFTs) which improved the overall performance just a little bit more.

Though I am pleased with the Predator results I decided to go further and buy a custom tune. Lewis Eaton is a custom tuner who can write complex tunes which he e-mails me and which I can then load into the car via my Predator. My "DiabLew Tune" made the car more driveable (more low-end torque) and improved the powerband across the board. Since the Predator can log engine functions in real time, Lewis sends me a file, I drive on the new tune for about a day, run a log and send the log to Lewis for analysis. He then tweaks my tune file. After about three rounds like this we arrived at a really clean tune for my car and I'm pretty pleased with the results.

Lewis can be contacted through his website:

Plans update (December 2011): I've decided to take the modifications in a slightly more serious direction. I still won't do anything that can't be relatively easily undone. This Winter I will be installing JBA shorty headers, JBA catted midpipes and a Magnaflow 2.5" cat back exhaust. Future mods will include adding a Harrop rear differential cover and a full Lovell's Eliminator suspension.

July 2010:

Thus far the only modifications I've performed are to install a Casper's Electronics Skip Shift Eliminator and to have the windows tinted.

The Skip Shift Eliminator is a small electronic device that is installed in the transmission wiring loom which deactivates the skip shift feature of the manual transmission. This means I can shift from first to second even at slow vehicle and engine speeds. The skip shift feature on these cars is exceptionally annoying so it is good to have bypassed it.

The SSE consists of a resistor that is plugged into the factory harness terminal to fool the system into thinking the proper conditions are met when trying to activate the skip shift solenoid. Also included is a weather plug which is inserted into the plug on the solenoid in the transmission to keep dirt and moisture out. The now loose harness is simply zip tied to something to keep it from swinging around causing damage.

Note: the SSE has been removed as of late August. Since I now have a DiabloSport Predator, I can remove the skip shift via a tune.

August 2010:

A deal came my way on a set of JHP dash top gauges so I bought them earlier than planned. But I saved nearly $200 so jumping the gun to grab this deal worked out great. The install went as good as can be expected. I did get a lot of great help from Denis at the JHP office in California who helped me with some technical issues during the install. He stayed on the phone with me while I did the wiring and helped me get it done without a hitch. They work great and the illumination matches the main gauge cluster perfectly.


I got a DiabloSport Predator tuning computer. It is proving to be a fun little tool. I have done some diagnostics and tuning. Most things have gone well and I've even tried my hand at adjusting the fuel trims and thus far I've had good success improving the power output on the car. I have found an outlet for 92 octane pure gasoline (no alcohol) so I have tried the more aggressive tune with some success. I really like using the tool to view the real time fuel trims, air fuel ratios and other statistics while the car is in use. It is also fun to load the files into the tools provided by DiabloSport that allow you to graph the data to really see what's going on as you drive.

September 2010:

The Lovell's parts arrived. I recently installed the 370mm stock height rear springs and urethane radius rod bushings. Both jobs were completed in a single morning. The rear subframe and differential bushings will be installed at a later date.

The springs are shown below next to the stock spring I removed. The originals were beginning to sag but the new ones brought it right back up and into spec. I installed the radius rod bushings at the standard setting and the caster is perfectly in line with factory specs (7.75 degrees +/- 1.25 degrees). It handles noticeably better and the steering feel and braking feel are much more precise.

The fuel line arrived so I installed it. It took about 5 minutes. This is an upgrade every GTO should get. This wonderful Russell braided stainless steel fuel line (part number 651121) is inexpensive and replaces the factory line that is way too fragile and commonly gets cut into by the fuel rail covers. The first photo shows the new line installed with the original factory line next to it for comparison. The original line is plastic with a thin rubber covering. The next photo is the new line by itself and the last one is how it looks with the fuel rail cover reinstalled.

October 2010:

I had never planned to change the stock shifter because I was pretty much happy with how it works, but a chance came my way to buy a Lou's Short Stick so I thought I'd try it out. It isn't a whole new shifter, but it is a shorter handle and leans the knob toward the driver more. It is also a solid stick which replaces the stock stick which is a steel shaft encased in rubber which is embedded in a steel tube which is then bolted to the shifter on the transmission. This rubber does a great job of insulating out drivetrain noises and vibrations but does provide a somewhat rubbery shifter feel.

The LSS is a simple solid steel stick that bolts direct to the shifter mechanism. The version I got allows for the installation of the stock knob so other than the lower position of the knob and slight tilt toward the driver, it doesn't look a lot different than a stock installation. The LSS provides a very noticable improvement in shifter feel and allows for more positive and precise shifting. The process of shifting feels much more mechanical and firm. It does transmit a slight amount more of drivetrain noise into the cabin but it is hardly intrusive.

Others have commented that the LSS install leads to buzzing or rattling of the shifter handle but I've not experienced that yet. If it does crop up I will install a thin rubber gasket at the metal-to-metal contact spot to slightly better insulate the handle from drivetrain noise and vibration.

Here is a photo of the interior with the stock shifter:

And after the LSS was intalled:

I finally got the opportunity to install the rear subframe bushings and the differential bushing. Everything was fairly easy to accomplish, it just took a little time and a few good tools. I noticed a difference with the rear bushings more dramatically than I did when I installed the front radius rod bushings. The ride didn't change at all, but I have noticed an uptick in NHV and noise transmitted to the interior of the car. Nothing outrageous, but you do hear the thumps from road imperfections more clearly and the mechanical clunks the rear axle makes when shifting gears is somewhat more pronounced. The benefits were immediately noticeable in a more solid and connected feel in cornering and accelerating. The manufacturer claims these bushings will help reduce wheel hop but I haven't tested that yet. If the slight increase in noise become annoying I can always reinstall the original rubber bushings as they were all still in fine shape.

March 2011:

I installed a set of Energy Suspension front and rear sway bar mount and end link bushings. The front pieces were a snap to install and the rear end link bushings were no problem. The rear sway bar mount bushings were a bit of a challenge to change in, but I got them in without too much drama. No pictures on this mod since there really isn't much to show, I swapped in some black poly urathane bushings to replace some black rubber ones! The front mount and end link rubber bushings were beginning to show some serious wear so I'm glad I changed these. I didn't really notice much of a change in the handling of the car, but this is a pretty minor change. At least I know I won't have any of these bushings failing anytime in the near future!

April 2011:

I finally got an oil catch can. I got a good price on an Elite Engineering catch can and it is very nicely made and a snap to install. The catch can connects to the crankcase breather system to catch the oil that is contained in the crankcase fumes and separates it out so the intake system and valves are not gunked up with oil. Oil sludge on the intake system can lead to deposits on the intake valves and effectively lower octane on the air/fuel charge leading to knock and detonation. Such a system should have been installed by GM on all LS engine.