Engine Tune up.

[Fernando Mendes]

Anyone has the sequence of flat head six Engine tune up?

[Jim Gaspard]

I haven't been here yet, but Don Coatney posted this some time ago. The Search feature on this Forum makes it a cinch to find a technical answer if its been posted before.

"I think you are making this way too difficult. With your harmonic balancer top dead center timing mark is lined up with the pointer on the timing cover remove the distributor cap and note the position of the rotor. It should be pointing to the location of the #1 spark plug wire. Normally this is near the 7:00 O'clock position. If it is at the 1:00 O'clock position you are still OK but you should rotate the crankshaft one revolution and this will place the rotor at the 7:00 o'clock position. Once you have established where the rotor is pointing at the number one position than connect the spark plug wire to the hole where the rotor is pointing and to the number one spark plug. Next place the number 5 sparkplug wire in the next hole clockwise in the distributor cap and connect this wire to the number 5 sparkplug. Continue with number 3, next 6, next 2, next4. The firing order is 1-5-3-6-2-4. Once this is done engine should start. Then you can dial in your timing to where the engine runs the best with no pinging. Don Coatney"

Jim Gaspard

[Tom Skinner]

Fernando,

I have a 250.6 6 Cylinder Flat Head it tunes as follows:

Firing Order 153624 for a 6 Cylinder Flat Head, #1 is at 7:00 on the Distributor.

Set Points at .020 set Plugs at .025

Set Timing until you hear a slight pinging of the plugs at full throttle

between 10-25mph, Use a Vacumm gauge to Set the Carburator.

Set the RPM's first around 450-500 then Set the mixture screw until

you get the highest reading in inches - say 20" to 21".

Tom

[grey beard]

Ohe last item that no one usually mentions: The SSSEQUENCE of your tune-up items is critical. Always adjust the points before setting the timing, for any change at the points affects timing. When you set your timing, no need to disconnect the vacuum line to the carb, for no vacuum is present here at idle. One last thought on timing; initial timing can only be set properly with the engine at hot idle speed. If idle speed is even a little too high, the centrifugal advance can tip in and give you a wrong reading with your timing light. You want to be mesuring only initial timing and not centrifugal or vacuum advance added to it. Keep the idle speed way down here, so it just ticks over.

After you are certain the initial timing is correct, THEN disconnect the vacuum line and check your centrifugal advance by watching your light and timing marks while you raise engine speed. Once you are certain that is working, then reconnect the vacuum line and check to be certain the vacuum advance unit is functioning. You should see added advance when you rev things up over and above wha was seen with he centrifugal advanc only. If you have an advance degree-type timing light, you can even check these two advance mechanisms for the proper amount of advance. Advance curve specs are typically listed in the shop manual. Very few people ever do these two tests, and both are critical to good engine performance.

Finally, and only after you are dead certain all the ignition adjustments are set as they should be, THEN adjust the carburetor as outlined above in this thread with a vacuum gauge. I would also suggest that this is an auspicious time to take a box wench and check that the carb-to-manifold flange is tight. You will never get the carburetor adjusted properly if it is sucking air - vacuum leak - at the base gasket area.

All the while you are doing this, you must readjust your hot curh idle dowward to the proper idle speed. This is true because as you get the mixture dialed in, idle speed typically increases, and needs trimming. These two adjsustments both need to be done with the air cleaner in place on the carburetor for best accuracy.

Happy motoring!