F-Body Pinion Angle

There are many theories, "experts," highly respected experienced racers, and thoughts regarding pinion angle. Count the stars in the sky and you can bet there are just as many ways documented to measure and set your pinion angle. Here at Install University, we want to give a clear and concise look at how we measure and set the pinion angle.

The goal of setting pinion angle is to have both the angle of the transmission and centerline of the pinion parallel with each other under full load conditions. This is accomplished by measuring the angle of the transmission and adjusting the angle of the pinion correctly.

Measuring your pinion angle
A digital protractor makes the job much easier along with an area clear of obstructions under the yokes. You will also need to be able to rotate the rear tires so you can rotate the pinion yoke so the rear tires must be off the ground but the suspension must be at ride height. It does not matter if your car is exactly level, just that it is safe to get underneath without the threat of rolling, shifting, or falling on you or someone else. Always face the yokes from the same side (driver/passenger) of the car when measuring. We choose to always approach the car from the driver side. 

Level the transmission yoke so the solid part of the yoke is level in the cross section. Place the digital protractor on the yoke of the transmission running parallel with the car. Record this measurement. In this case an angle falling from the front of the car to the rear of the car of 2.2 degrees was measured.

Level up the yoke on the pinion gear and place the digital protractor on the yoke running parallel with the car. The angle measurement in this case was 0.3 degrees rising from the rear of the car to the front of the car.

The transmission tail shaft angle is 1.9 degrees lower than the pinion angle (-2.2 + 0.3 = -1.9 degrees). When the car goes under full load and the transmission tail shaft raises up the assumed two degrees, both transmission and pinion angles are equal at zero. This puts the pinion angles in the same angular plane as each other and gives you the best possible scenario for your drive line.

Now that you know how to calculate your pinion angle there is one more variable that should be taken into account. The weight of the driver. Weight must be added to the driver seat equaling the weight of the driver before measuring the pinion angle.

At this point some reading this are yelling at their computer screen. "But the internet says I need a negative three degree pinion angle!" Yes, the interwebs do say silly things like this with everyone always perpetuating the incorrect idea.

When you raise or lift the pinion angle you are are directly rotating the rear lower control arm angle effecting the anti squat of the car. This may or may not lead to better tire grip depending on the car. Realize the angle of the rear lower controls arms are an important factor in traction. You can adjust the angle of the rear lower control arms with the use of relocation brackets. What that angle should be will depend entirely on testing you do at the track while finding out what works and what doesn't for your car.

Spring Test Roundup

How serious are you about your suspension? Chances are you are in the category of people where it does not matter when you start talking little details. Nothing wrong with that. But there is a group of people where these little details start to matter. Where you want to know nuances that seem trivial to normal people. If you are one of those people, keep reading.

Different brand springs for 1997 - 2002 GM F-Bodies were purchased and tested to observe the exact spring rates. The springs used in the test were 2011 BMR Suspension rear and front springs, Moog linear spring, GM Stock rear springs, and Hypercoil 160 linear.

We should first discuss what spring rates are and how they are measured. Spring rate is simply a measurement of force required to compress a spring over a distance. By applying a force and measuring precisely every one inch, you can get the spring rate throughout the operating range of the spring. The unit of measurement we are using for the spring rate is pounds per inch (lb/in). [More]

F-Body Front and Rear Spring Testing

Here is a sneak peek of the upcoming spring testing we have been doing in our labs.

Super Sport Hoods: Do they really supply cool air to the engine?

While doing some testing on a 1998 1LE SS Camaro I noticed that the intake air temperatures (IAT) acted strange.  The temperatures were up and down throughout the test runs.  It really did not hit me what was going on until middle ways through the testing.
The Super Sport hood directs air into the scoop on top of the hood where it then curves back around and heads toward the front of the hood where it makes another turn into the front of the air box assembly.  There is a rubber seal that "seals", use that term lightly, the intake assembly so that it does not let any air from the engine compartment in.  This is clearly meant to be a cold-air-induction setup.  This is also a long distance for air to travel from the time it enters the hood scoop to when it makes it way into the air box.   
The IATs were around 115 °F when we first started the testing.  Once the car had been in motion for a mile or two the IATs dropped into the middle to low 90 °F.  Wow!  I knew that it just didn't get cooler outside all of a sudden!  So what would cause this phenomenon to happen?
That gave me the perfect hypothesis that needed to be tested.  While your car sits at idle the engine temperature rises.  The hood soaks up the heat and can not dissipate the heat quick enough to stay cool.  This causes the air that passes through the SS hood to soak up the heat from the hood.  By the time the air gets to the air box you have heated air.  Once the car goes into motion the hood is able to dissipate the heat to the outside air fast enough to lower the temperature of the hood.  This would cause the air that enters the hood scoop not to heat up quite as much which would keep the air cooler.  
We never expected to have such a lag in the time it took to get cool air into the engine once we started driving.  The least amount of distance it would take the car to travel before getting cool air into the engine was one-half mile.  Ouch!  That is entirely too long, especially for us quarter milers.
Do your self a favor and get a ram air setup if you are looking to cool your intake temperatures down quicker than a half mile.  Our fast toys ram air system gives us ambient intake temperatures from the time you start your car to the time you turn it off.  It does a great job over the free ram air mod too.  So it is a win-win situation to purchase a ram air kit if you really intend to get those temperatures down on the SS or Z28.

Where did this "miss" come from?!?: After a night of racing we set the SES light

A trip to the drag strip was on the schedule so we had to make sure that "good" gas was in the car's gas tank.  Race gas (110 Octane) is not readily available in our neck of the woods.  This forces us to use what resources we have available to us and that means octane boosters.
Before this bottle of Super 104 Octane Boost was poured in the gas tank we want to give some background information on the history of the previous tank of gas.  Super 104 Octane Boost was added to a full tank of premium gas a full eleven days prior to this fill up.  We managed to burn five gallons out of the tank before the car got parked for the eleven day period.  The car had around eleven gallons of gas in it with a bottle of Super 104 Octane Boost.

Super 104 taking a second to strike a pose

A quick stop to Wal-Mart for a bottle of Super 104 Octane Boost was on the agenda before making it to the track.  We thought that the car had sit too long and the gas might have went downhill.  With this in mind a bottle of Super 104 Octane Boost made perfect sense.
Two Auto Tap logs were taken out of the six runs down the strip and despite the very humid and hot conditions, knock retard was at a minimum.  Everything was looking hunky-dory at this point and we gave no thought to adding the "black bottle" to the gas tank.
The next day we took a short road trip to Nashville, Tennessee.  During the 130 mile trek the car was a little rough.  There was a short jerk that would show itself from time to time.  At red lights you would have thought we had a .700 lift cam installed.  The smoothness of the LS1 which we were accustomed to experiencing was gone and was a herky-jerky type of ride.  The actions were just shrugged off until we noticed the Service Engine Soon (SES) light illuminate.  At this point the car had our full attention and we were all ears.  The SES light showed it self at idle waiting on some friends to arrive.  We immediately had several theories to what we though was going on.

It looks harmless enough just standing there looking innocent

My first thought was that the spark plugs had fouled because of all the octane boost in the gas tank from the night before.  A similar situation had occurred on our 1999 Chevrolet Silverado.  The only difference between the two is that it took three consecutive fill ups using Super 104 Octane Boost to foul our plugs.  The other idea was that the Magnecore spark plug wires had finally give out.  We do not run the metal heat shields on the wire boots and many people have reported that the wires have dried out and cracked from being exposed to heat on the LS1.  Since we did not have our computer and Auto Tap cable, we just drove the rest of the day with the rough performance and headed home late.
First thing the next morning we found out that we set two P0300 diagnostic trouble codes (DTC).  One was set at idle and another at 68 mph.  Using Auto Tap we viewed the Misfire History of all eight cylinders.  There were 2 or 3 misfires on several of the cylinders within 60 seconds of starting the monitoring.  This gave us strong reason to believe that an ignition problem was present.
At this point we had ran all the gas out of the tank but 4 gallons.  We added five gallons of premium gas back to the tank and were pretty confident we had diluted the Super 104 down to near nothing.  This time when the attention getting SES light appeared there was no fear because Auto Tap was up and running while taking a short 70 mile drive down the interstate.  We set two more P0300 DTC's.

Notice the red color

The next question that had to be asked was, "Should we change back to the stock wires or do a plug change?"  We pulled the spark plug in cylinder three and we found our answer.  The tip of our plug was red and covered with black gunk!  Wow!  Off to the parts store to pick up eight copper NGK TR-55 spark plugs.  We changed the spark plugs in around one hour and fifteen minutes and enjoyed doing it.  Our arms would have told a different story.  
After the drivers side was completed it was obvious that the spark plugs were probably the cause of the whole misfire situation.  The swap on the passenger side of the car confirmed that we had a major problem with the color of the spark plugs.  It should be safe to say that red is not the color you want to see on your plugs.
We started the car up and immediately noticed that our car was smooth as silk.  A short drive down the road confirmed that we had removed any sign of the miss we had experienced.  No more herky-jerky dance moves for our LS1, we were back to normal!  Wooo hoooo!
I believe that it is evident that Super 104 Octane boost should not be used in back to back fill ups.  Especially if you still have some Super 104 Octane Boost in the gas tank of your car when you pour in more octane boost.  You will probably find yourself with a LS1 that runs smooth as sandpaper.