Chasing Gremlins

Old cars were not perfect when they were designed. Even the Jaguar XKE had its issues. Now these same cars are much older and with time comes age related flaws......

Inattention also breeds issues. Unused seals wither and crack, hoses get old and vinyl begins to look like the floor of the Mojave desert.

Finally, when you're away from something for so long, you forget how it should operate, how it should sound and the way it really should perform.

Inattention over the years really wore down my '73. All the things above happened and in many bad ways. The good news however is that I like fixing things. A couple posts previous, I listed a huge list of things that I've set right on the car - and had fun doing it.

All through that work, as I drove the car, it seemed to run well, but it was somewhat down on performance. Idle kept climbing, power seemed good but not great. Finally, it backfired and popped at odd times.

Then I read on the 6Pack forum about a different way to set the timing on a car. Instead of using a timing light like in days of old, the thing to do is to use a vacuum guage.

So the process is simple. Get the car warm and at an idle of 900rpms. Then take a gauge reading from the vacuum gauge with it attached to the intake manifold. Simple!!!! With the cam I have installed, the initial goal vacuum measure was/is 13HG. Stock Sixes start usually at around 18HG!

Not so fast..... The car warmed up easily enough. 900 rpm idle was the issue. As I mentioned above, the idle has been climbing over time, to the point that the car was now idling at about 1200 rpms. Not a lot of fun. And not very good for getting good readings. So first order of business was/is getting the idle right.

I decided to give it a whirl first and get my reading. First reading was 6HG!!!!!!! Yowza! Severely retarded my ignition was. I started advancing the ignition (twisting the disty) and got to 10HG, but that was with an Idle of 1400RPMS. The test drive however told me I was on to something. The car was definitely not tuned correctly before - and I did not know it because it had been so long since I had driven it. With the ignition advanced, the thing had loads of power. Stump pulling power, the power of a modified TR6!

With help from the 6Pack forum members, I began chasing down the cause of the high idle. It eventually took all weekend, but I found that most of the cause of the high idle was an improperly rebuilt bypass valve on the Zenith Strombergs.

With the right gasket in the valve, the right seal in the adjuster (in the background in this pic), I finally got the car to idle at approximately 950 rpms and 12HG. A pretty cool number. So better performance is on the way!