Solving a Misfire

It's really important when doing driveability diagnostics that you start with the basics first and work toward the more complex causes. Putting the car back into it's "as-built" configuration with regard to both settings and parts is key not only to solving the issue(s) at hand, but also in giving you a good base platform from which to continue diagnostics.

Whenever you're putting an unknown engine (and car) back into service, the first thing to do after safely achieving oil pressure (see the related secion in the Technical Advice: Engine page) is always an oil and filter change. Then perform a dry and wet compression test performed with the engine hot.

Next on your list is a valve adjustment and on our engines it's a good idea to set the exhaust valves at a loose .012" or a snug .013", especially the #2 and #3 exhaust valves. This helps the valves run cooler, keeps them from burning so easy, and helps them hold an adjustment longer. Consider that there is no longer leaded fuel, so the exhaust seats are getting hammered and are receeding (which tightens up the valve clearance and eventually can cause the ex. valves to burn).

Once you've got these main steps taken care of, you can do another dry and wet, hot compression test. This will give you a good idea of the engine's condition. A leak-down test will give you an even better idea of how well the piston rings and valve seats are sealing. Remember to hold the throttle wide open during any compression test and with our engines it's nice to hold the carb piston(s) fully up. Then crank the engine over until the compression gauge needle stops rising.

From here it's time to replace distributor cap, rotor, points and condensor. Next is spark plugs and plug wires, making sure not to fit some wiz-bang set of either, especially the Bosch Platinum plugs or the junky 7mm silicone wire sets sold at the schlock auto parts stores. During this stage, you'll be setting the ignition timing and 5-8 degrees advanced (with a timing light) is a great place to start. You can dial the timing in later. This is a good time to check the vacuum advance and mechanical advance function of the distributor. Both need to be working and the weights inside the distributor need to be oiled.

Fuel hoses and fuel filters are next on the list. Including those back at the fuel pump. While hoses are off the lines should be blown through with compressed air to make sure they are fully open. Generally, all coolant hoses, belts, air filters, coolant and an engine coolant thermostat are done now as well.

Last on the list is carburetor work including syncronizing them if your car has dual carbs, and setting the mixture and idle.