Art and Lucy, the Never-ending Engine Story.

Some people name their cars, motorcycles and recreational vehicles. We named our new home Priscilla from the Australian movie Priscilla, Queen of the Desert. When we started living in this 1987 Rockwood in the fall of 2011, it moved under its own power and that was about it. Since then we’ve slowly, as finances permit, upgraded the control systems on the refrigerator, furnace and 12v power system. We’ve also installed new tires and brake pads, a parking brake cable and lower ball joints in the front suspension. Along the way, again as finances allow, I’ve been trying to get our Chevrolet 454 Cu. In. engine to run properly. Up until recently there were occasional good days but for the majority of our driving the engine ran on 7 cylinders at best. Just as Lucy van Pelt would pull the football away from Charlie Brown our beloved home would do the same to me regarding what is a fairly pedestrian installation: a Chevy 454 in a truck chassis. What could be wrong?

I’m 58 years old and plugging away at my 59th as we speak. Back in my hay day I was no stranger to the 454. At one time I owned a set of 3 Cadillacs, a Coup de Ville, a Fleetwood Brougham and a division window Series 75, the factory formal car. After a little dispute between two friends who wished to remain friends Lynn and I were asked to dissect a 454 from in a pick-up truck to do a root cause analysis. So I went into this cash poor but feeling pretty well qualified for the task.

First things first you start with an air-filter, fuel filter(s) and check the ignition timing. Check. A good rule to remember about this technology is that as sexy as carburetors are to play with, It’s Always the Ignition! So plugs and plug wires are purchased and installed. Good to go! Ummmm, no. So New Cap and Coil! GM came up with this self-contained ignition system. Sort of a distributor in a can, where the ignition coil is built into the distributor cap, the distributor receives switched 12VDC and 8 high tension ignition wires lead out to the spark plugs. So if you install a new distributor cap and coil you’ve pretty much replaced everything. There’s a solid state module that takes the place of traditional ignition points and that is good or bad but I replaced it just to make sure and then I changed the condenser, that part you need whether you use points or magic to start and stop the primary current. Why do you need a condenser? Because an ignition coil has a characteristic inductance and with the properly sized condenser you can make the coil ring like a bell so each spark plug sees a glorious shower of electric sparks instead of one that goes Meh? Shower of sparks equals good fire. Meh? equals dead cylinder. Hopes up! Hope dashed by reality.

So now the exhaust note gets louder and I replace what turns out to be perfectly good exhaust doughnuts. The air injection reactor plumbing has rusted away at the exhaust manifold so I spend one summer removing the plumbing, all of one afternoon. Then the threaded ferrule in the exhaust manifold. turns out to be 22.5mm by 1.5 threaded oil drain plugs and I order up a drill and tap. Eight ports and two weeks later that problem taken care of but I’m back to my (expensive, motor-home-only) not so new anymore ignition cables. The jets of exhaust gas from the rotted A.I.R. plumbing has melted some of the ignition cables and insulating spark plug boots. This is the second set of ignition cables specified for the GM 454 P30 chassis motorhome. AARRRGGGHHH!

We go from where we were for the summer to a months stay where we have to climb a couple of steep slow hills and cross a bridge rated at 2 tons. Barely made it up the hills. So now it’s time to start looking deeper into the fuel system. The problem comes and goes so maybe the problem is fuel contamination. The dirty little secret about gasoline-alcohol blends is that they pull water from the air and when the alcohol has enough water tucked away all of the alcohol and all of the water settle to the bottom of the fuel tank. So because it does no harm and is a modest improvement I install a Wix brand water-separating fuel filter. The Wix 33123 is a big canister type fuel filter that is about the same form factor as a spin on oil filter but has a drain cock in the bottom to drain of accumulated water. Hope hope hope wish wish wish no luck. Time to take the carburetor apart.

Round one, I ask Lynn to do it because he’s meticulous but it turns out that he knows even less about the GM Quadrajet than I do. No dirt. No better. So I do the reading, each session ending when I start to bang my head against the table top. GM’s bean counters decided to use one carburetor design for everything GM made. The variations are endless even before you add in the generational changes. Luckily in 1986, the last year of carburation for GM the Quadrajet had settled down into a fairly flexible yet simple design.

Now during October 2015 I had a chance to take care of our radiator leak. While I was in there I changed out the mechanical fuel pump. The late 1980s Chevrolet P30 chassis use two fuel pumps, an electric one in the fuel tank to lift the fuel to the engine and a mechanical engine driven fuel pump to supply fuel to the carburetor at the required pressure and volume.


Long story short, it was a bad spark plug cable. Brand new but bad.

About Art

55 years old. By training, ability and experience I am a master toolmaker. My most recent projects include designing and building a process to grind a G rotor pump shaft with four diameters and holding all four diameters within plus or minus 4 microns of nominal. This was an automated process using two centerless grinders refitted to my specifications using automatic load and unload machines plus automatic feedback gauging. I also designed and built an inspection machine to check for the presence and size of a straight knurl on a hinge pin using a vision system for non-contact gauging.
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