I always was and still am the type of guy that does not embrace only one kind of machinery. My interests are very eclectic. I can get just as excited about an economy car exceptional at sipping fuel as a high output drag race engine or a new style hay baler.
I pride myself on getting a machine to run better than it did from the factory. It makes little difference if it is an eight-horsepower Tecumseh Snow King engine or a washing machine. When you are of this ilk, you embrace an engineering term though it is meant to be used in a slightly different context. That is degrees of freedom.
According to the McGraw-Hill Dictionary of Engineering, it means any one of the number of ways in which the configuration of a mechanical system can be changed.
To someone at the bottom of the engineering food chain as I am, I call that tuneability. I love being able to adjust and tune something. The more tuning points there are… the happier I am.
Due to this, I always loved carburetors, especially ones with a multitude of adjustments. There was no better way to spend a summer afternoon as a farm kid than taking a carburetor apart and reverse engineering it and playing with the adjustments. The linkages or pivot points would need to be tweaked with a gentle touch from a pair of needle-nose pliers on some models. Others allowed changes via a treaded component or screw.
They were all adjustable. It was just a matter of how hard you had to look to find it.
Back then, we had a Gemco Giant lawnmower with a 3.5 horsepower Briggs & Stratton engine circa 1954 (the year my family purchased our farm). It was already quite old when I was introduced to it.
Unbeknownst to my father, I took the engine apart when I was 13 years old and ball-honed the cylinder, scraped the carbon from the piston, and fitted new rings. I then proceeded to port the cylinder head with a Dremel tool I had. The impetus for this was rooted in “Car Life” magazine’s issue that espoused the virtue of airflow improvements in an engine.
I then hand lapped the valves with some compound in the barn and a wooden valve dowel I found near it.
I put the engine back together, and much to my shock, it started on the second pull! All was not well, though. It did not sound right under load.
Nervously recognizing that my father knew nothing of my foray into engine building, I hoped that the carburetor was now too lean due to the increased airflow. I pulled the carburetor off and, with a book I had purchased about a year earlier from the Western Auto store in town (I loved that store!), identified the main metering circuit.
I raised the float level to pull-over sooner. With a hand-crank drill (I did not want to ask my dad for his electric drill and let him know what I was doing), I opened up the main jet, albeit a little cock-eyed.
Boy, did that Briggs now run! I then let the grass grow a little longer to test it out (my version of a dynamometer) since I knew it used to struggle with the lawn that height. My father could not believe how the old mower suddenly laughed at the grass it used to wheeze at. I told him I tuned it up and put in new breaker points and sharpened the blade.
Fast forward about six or seven years.
You can now imagine how devastated I was when I read that the new 1981 GM Rochester carburetors would be electronically controlled, and no adjustments could be made.
No carburetor adjustments… what is the use of living?
The automotive rumor mill was ripe with stories even though no one had yet seen an electronic Quadra-Jet or its two-barrel brother. “All computer-controlled, son. You might as well throw away your tools”, I was told by the old-timers.
A George Orwell-style prediction of a changed world four years earlier than the title of his book.
It was going to be 1984 in the fall of 1980 when the 1981 GM cars hit the showroom floor. Back then, the car magazines would put photos with callouts of engine components as part of their new car issue. Today all they talk about is connecting a smartphone to the vehicle.
Sure enough, the image in “Popular Mechanics” showed no mixture screws. It had sensors, a solenoid, and an idle speed control motor. What a nightmare.
They, too, regurgitated the no adjustments mantra.
Everything was factory set. To my way of thinking, if the factory could set it, then I could unset it.
I departed on a quest to learn about these new carburetors. It took me to the GM Training Center in Tarrytown, New York, and the AC-Delco training room of Mr. Richard Hipp. I signed up for a three-day class.
Much to my surprise, the electronic GM carburetor was even more adjustable than before! I could not help but think of how great our Gemco Giant would have run if this carburetor design were on it. The electronic carburetors were a dream come true to me.
Where could you find a carburetor that had a treaded and stepped adjustable air bleed?
Engine vacuum was removed as the control for the metering rods. A duty-cycle solenoid that pulsed at 10 hertz replaced it.
You could easily control the lean authority and the rich fuel flow rate. The mixture screws worked in concert with the dithering primary metering rods. All that was required was a dwell meter for a perfect air/fuel ratio adjustment.
A dwell of 30 degrees meant the metering rods were spending an equal amount of time in and out of the main jets. The idle speed control motor guaranteed a rock steady rpm regardless of the load evoked. The choke spring tension was no longer tunable, but the fast-idle speed and pull-off angle were easily tweaked.
The secondary side of the QJ was the same as before and could be fine-tuned if you understood it. I was in love.
I came back to the farm feeling as if I were Columbus and discovered that the world was not flat. Few wanted to listen, though.
While in college, I took a job in a Buick dealership and fixed all the drivability problems. I do not want to brag, but I could get an electronic carburetor 3.8 V-6 Buick to idle so smoothly at 550 rpm in drive with the A/C on that the customer would think it stalled.
If it were not for Mr. Hipp and the Rochester carburetor that “could not be adjusted,” you would not be reading this today.
Sadly, Mr. Hipp passed away in 2003 and was buried on my birthday. The knowledge he imparted to this baby face farm kid in the front row that would come early and leave late still lives on today.
Mr. Hipp, I owe you a debt of gratitude.
Please think of this story when your young son finds his way into your toolbox.
