Garage Classic: Sun Performance Analyzer 1115–The Most Fun under the Sun


(first posted 8/31/2015)   There’s really not much to say about this scene other than to ask you to picture the happiest, geekiest 38-year-old man in the world hooking his Dirty Dart up to the old Sun Machine.  It’s Christmas in Michigan whenever I pull it out of its dusty corner.


There is no practical reason for my having a Sun oscilloscope from the ’70s.  It doesn’t do much that my portable Autolite primary oscilloscope and my ’70s Craftsman engine analyzer don’t do (in combination), but it does it in such a big, flashy, colorful, happy way that I can’t help but pull it out every once in a while, even when everything’s running pretty well.


Pragmatism is not necessarily a hallmark of my personality anyway.  On the other hand, the oscilloscope only set me back $50, delivered, from the local Ford dealer, where it had been collecting dust for decades.  Since I’m a man with points distributors, I said, “why not?”.  If nothing else, it’s got the look.


The reason I pulled it out is that the Dart has a very light, variable miss.  The scope tells me there’s too much timing variation between cylinders, so it’s probably a slightly worn distributor.  Therefore, I’m switching to electronic.  I already have an electronic distributor lying around, but it’s the age old question: Mopar or HEI?  This has been discussed here before, and I know that HEI is superior, but I decided to order a Mopar Orange box kit from Jegs, because it has the whole harness I’ll need along with the ignition box and correct ballast resistor. Simplicity of installation won the day this time out.

Another fun feature of the Sun machine is its ability to kill cylinders individually (or the whole engine) at the push of a button.  As a result, I discovered that the Dart’s weakest cylinder is number four.  That may be, however, a result of the distributor.  We shall soon discover the answer.


Speaking of the Dirty Dart, I just bought a set of 15″ steel wheels for it, with matching tires.  It looks infinitely better with those more aggressively sized hoops filling up the wheelwells.  Freeway revs have dropped by nearly 500 RPM, and the speedometer and odometer are now nearly accurate.  I also replaced the axle bearings and seals, ball joints, and shift shaft seals so far this summer.

It’s been a fun evening fiddling with two of my flashy, extraneous toys.  After all, there’s nothing better than exhaust smell on your clothes, so if you get a chance to buy a huge Sun machine, do it, by all means.