does this seem like a good way to time the engine.


Older engines can't always be tuned or adjusted per their original guidelines. Timing chains can slip over the years, harmonic balancers can move, and the bottom line is you are no longer able to verify where top dead center is using the old methods. Plus, with today's fuels, it's more difficult to reach the point where your old engine performs both efficiently and reliably without sacrificing performance. Following the steps below, you will be able to minimize pinging, have reliable starting under all conditions, and easily get maximum performance from your engine using today's fuels.

1. Connect a vacuum gauge to a vacuum source directly on the intake manifold. Do not attach gauge to ports being used by any other device. Plug any vacuum lines you remove from manifold to make this connection.

2. Loosen the bolt securing the distributor so you can turn the distributor to adjust the timing.

3. Start the motor, let it warm up to normal operating temperature, and stabilize at normal hot idle. Using the idle speed adjustment at the carburetor, set the idle speed as low as possible without stalling the motor. Disconnect the distributor vacuum advance and plug the line.

4. Keep in mind when adjusting the timing, you have to turn the distributor clockwise to advance and counter-clockwise to retard.

5. While watching the vacuum gauge, slowly turn the distributor clockwise (advance timing) and look for a maximum reading on the gauge. For instance, if the reading on your gauge peaks at 18 inches of vacuum, that is the maximum for your engine. (The normal range could be from a high of 20 inches to a low of 15 inches, depending on the internal condition of your motor). The reading will drop off if you advance too far, so turn the distributor counter-clockwise (retard timing) to go back to the peak reading on your gauge.

6. Once you have established the peak reading, retard the timing (turn distributor counter-clockwise) to reduce the reading by about 1 inch to reduce ping. You may need to reduce the reading by 1.5-2 inches total, or even more, depending on the fuel available in your local area. Let your engine's performance guide you. If you had the same 100 octane fuel in your tank that was available when these cars were new, you would most likely leave the timing at the peak vacuum reading, but even when these cars were new, there were issues with fuel. Old Technical Service Bulletins (TSBs) exist that recommend retarding timing due to engine ping, so this was a concern even back when the cars were relatively new. We've included a chart on Engine Vacuum Gauge Diagnosis (link opens a new window, disable any pop-up blockers to view) to help you determine what the gauge readings mean.

7. Stop the motor and tighten the distributor hold-down bolt. While you still have your vacuum gauge hooked up, it is a good time to set the idle mixture needles on the carburetor. The adjustment is normally made with the two screws at the front base of the carburetor, depending on model. Turning the screws in will cause a richer mixture, turning the screws out will cause a leaner mixture.

8. Start by turning the two screws in fully then backing them out about 1 1/2 to 2 turns. Start the motor and check the vacuum gauge. What you want to see is a maximum steady vacuum reading. At the beginning stick to adjusting just one screw at a time to achieve maximum vacuum. As you turn the screw in you will see a reduction of vacuum on the gauge. When you turn the screw out you will see an increase in vacuum but only to a point. If you get the mixture too lean the vacuum gauge needle will start bouncing around. Your goal is to have maximum steady readings. Then repeat the process for the other screw. To fine tune, adjust both screws slightly while watching the gauge.

9. Once you have achieved a satisfactory idle mixture, set the idle speed to specification, then remove the vacuum gauge and reconnect any vacuum lines you removed. Don't forget to reconnect the distributor vacuum advance.

Test drive your car and listen for any ping under light acceleration as well as under heavy acceleration. Additional retarding of the timing may be necessary if excessive pinging occurs. You should hear a very slight ping under light acceleration, and none under heavy acceleration. Your engine is now optimally timed to run on today's lower octane, no lead fuels.

 

Good stuff! #7 got my attention only because I recently replaced my Holley with a Edelbrock Performer Series carb. On the idle mixture, out of the book, it says to provide a leaner when turned clockwise and richer when turned counter clockwise. Are other carbs different?

 

"Older engines can't always be tuned or adjusted per their original guidelines. Timing chains can slip over the years, harmonic balancers can move, and the bottom line is you are no longer able to verify where top dead center is using the old methods. Plus, with today's fuels, it's more difficult to reach the point where your old engine performs both efficiently and reliably without sacrificing performance. Following the steps below, you will be able to minimize pinging, have reliable starting under all conditions, and easily get maximum performance from your engine using today's fuels."

The method described will work, but ...

Timing chains don't slip, they stretch. Yes, the marks on the balancer can move making it hard to find TDC. But if you have these problems, you will have more than just ignition timing problems. Cam timing will be thrown off too, due to the stretched timing chain. If the balancer is moving, it will eventually come apart. I guess what I am saying is it would be better to fix the underlying problems than just work around them. Only then will you get the best performance out of the engine.

 

On older engines with older carbs the idle mixture screws control fuel flow. So in(clockwise) is leaner and out(counter clockwise) is richer. On the newer emmission carbs the screws control air flow to in is richer and out is leaner. So #7 is wrong for and older engine and carb combo. Also anytime you get to rich or lean of a mixture the vacuum will be irratic because the engine isn't running right.

 

Makes a lot of sense. I know these FE's can be tricky to set the timing right. Thanks for the info...!

 

But, where is the actual timing supposed to be set at, per the emission control information sticker?

 

The vast majority of FE engines don't have an emissions sticker. 50s and 60s engines don't have them and alot of the 70s engines don't either. Intitial timing on most FE engines should be in the 6 to 12 degrees BTDC. I don't like to set timing by intitial. I set it by total mechanical advance, no vacuum. Just run the engine up to about 3500 to 4000 and watch the pointer, you should get a total advance of 30 to 35 degrees. If it rattles (pings) under load at 35 degrees back it off till it doesn't ping anymore. Check initial afterwards so you can set it without reving the engine next time.

 

So, I can use a dwell tach to get the RPM, right?
Then all I have to do is use the timimng light and set the timing by rotating clockwise?
My truck will run at high RPM, on the highway for 15 miles, before it wants to lose momentum and by the time I pull over it will low idle and shut down. Give it a minute and it will fire up and I will get off on the next exit and run the stop and go route.

 

Or, is it a stall RPM?
Since I run at least 3500 RPM at 55mph. I also am at 3rd gear, at 25mph. But, my truck will pull a house.

 

Doesn't matter what gears you have or what rpm's you run at. Total advance is total advance and will be the same no matter what gear you are in or whatever your stall speed is. Your high speed problem sounds like it might be getting hot. Do you have a thermostat in it. If you do is it working right. Then again if you have hot rodded the engine in the least you might need a bigger radiator.

 

I ran the RPM's to 1200, which is what the dwell/tach read. I used the timing light and it was at or around 30. I upped the ROM's and it was at or around 35. At 600 RPM it is at 14. I was thinking that I had the wrong wire in the timing gun, but when I did that I was given a shock. I had to go buy a new set of wires.

 

rob-you might also be running out of fuel pump capacity. I would look at the fuel pump to see if it is weak. Might also be a vapor lock problem.

 

30 degrees at 1200 is to much for mechanical alone, was the vacuum line still connected to the carb? 35 is a to much for a regular gas motor for the total advance without vacuum. You must check total mechanical advance without the vacuum hooked up. Plug it if you want but it won't make any difference unless you try to adjust idle mixture and speed with it unplugged. 14 degrees at 600 is ok if you have a short advance curve in the distributor. Number 1 cylinder is the right (passenger side) front cylinder, it is marked as such on the intake.

 

I was running with the vacuums connected. Once i put new wires it ran better. But, with this cold weather, here I will have to wait.

 

should I unplug the pcv valve to use for my vacuum guage?