[lilredex]

After you ARE ready for the cat. converter, don't make the mistake of buying too little, especially if it needs to pass an emissions test. Stay away from those short, universal cheapies because they don't have sufficient "guts" to do the job. They work fine until the idle part of the test and because they have minimal guts they cool off rapidly, the readings skyrocket and you fail.

Had this problem on an '89 with duals, one side had a cheapie converter.
The guy running the test was also a muffler shop (and had seen all kinds of failures due to short converters) so he was good enough to nurse it through the test and it just squeaked through. He held it at a very high idle for about ten minutes before the test (to really heat things up), then did a preliminary test (off line) to be sure it had a chance of passing. Not many shops are going to be this sympathetic towards old stuff and will just let it fail.

In Ontario, the emissions test is required every two years and the numbers get squeezed everytime making it more and more difficult to pass. Dec 2010 is the next challenge and I'll be installing new longer converters from my "buddy". He says about $150 ea will cover it (I install).

Have had problems in the past, never had a clearer understanding of what the problem was 'til now. Engine runs fine and uses very little oil.

EDIT: Don't know if I should really reveal this, but here goes. If you are very close to passing the test yet still fail, a few things you can do: retard timing slightly, re-adjust idle back to 750 RPM or whatever, disconnect the vacuum advance. Never had to do any of that last time on the '89, but have on other vehicles in the past to get through it OK.