Timing Marks on the 273 [66 Barracuda]

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Sellingthewind

Sellingthewind

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Hey all!
I have searched for a while, not sure I am using the correct keywords.

I cannot seem to get this car timed correctly. the timing marks are quite rusty and I cant seem to find it in our shop manual.

THESE PICTURES ARE WITH THE TIMING LIGHT AND THE CAR RUNNING.
This picture shows the timing (advanced? maybe)

At this timing, there were some backfires as well as some detonation.
20220721_182100.jpg


This is where it is adjusted now. I have gotten it close to running perfect but it does stumble on acceleration.
20220721_182352.jpg


can anyone point me in the right direction? the shop manual gives me the numbers, but no visual.

thanks all!
 
Have you checked to see if the outer ring on the harmonic balancer has possibly spun. Remember, most of the parts on the cars are 50+ years old & they eventually fail.
 
Get in there with a wire brush.

If your VERY careful. You can clean off the damper while the engine is running.

Then dab of white paint on the damper where the TDC line is.

Also check the FSM for how to time the car.

Usualy vacuumed advance removed and plugged.
 
Demonracer said:
Have you checked to see if the outer ring on the harmonic balancer has possibly spun. Remember, most of the parts on the cars are 50+ years old & they eventually fail.
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I really appreciate your reply. I had not thought of that. I am going to check this today.
 
Dana67Dart said:
Get in there with a wire brush.

If your VERY careful. You can clean off the damper while the engine is running.

Then dab of white paint on the damper where the TDC line is.

Also check the FSM for how to time the car.

Usualy vacuumed advance removed and plugged.
Click to expand...

You are super helpful on this entire forum!

The TDC mark seems to be the only mark I can make out. The manual i think keeps referring to "BTC" but it doesnt exactly specify on the rusted plate which mark is 5-7degrees before/after TDC.

Im sorry if I seem ignorant. I do have mechanical experience however its with Audi Timing Marks and Cam Gear marks. :eek:
 
You may want to remove the #1 spark plug and find tdc. Just to be sure your timing marks are still in the correct space.
Then add a new mark if the line is off, or tape.
 
trapster said:
You may want to remove the #1 spark plug and find tdc. Just to be sure your timing marks are still in the correct space.
Then add a new mark if the line is off, or tape.
Click to expand...
This was something i was thinking of doing asap, just to be 100% sure that balancer did not slip.
 
you may also need to check your vacuum advance on the distributor, also you should plug this while checking your timing.
 
Yes, unplug the vacuum line from the advance but be sure to plug the hose so you DO NOT have a vacuum leak.
 
16585999962869077850443103878279.jpg



Is your car a CAP car?

If so it might have a gismo like this.

If so the advance curve is very different then non CAP cars.

The 67 273 with CAP calls for 5 deg ATDC.which is very different than non CAP.

If you set it a 0 or 5 BTDC you should be ok to start.

Also if when you reattach the vacuum advance the engine speeds up there is carborator tuning that needs to be done.
 
I have run 10° or more before top dead center. Just check that itdoesn't ping. Today's gas isn't the best stuff. There's a lot of tricks with timing and advance curve.
 
Much of this is a cut and paste from past posts but covers the info you asked for.

The timing information is in the operators manual and the service manual.
You can look at mymopar.com for digital service manual.

Everything below assumes a factory distributor on a factory engine. Replacement distributors may or may not have the factory timing curve.

Initial timing is set with the engine at low rpm and the vacuum advance disabled. Always!
The rpm is important. If the rpm is too high, then the distributor will already be advancing.
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Needed is a timing light and a tachometer.
A 'distributor wrench' is handy but not neccessary - the hold down cap screw can be gotten to with sockets and extension or a box wrench with some creativity.

The initial timing of a '67 273 Plymouth is 10° BTDC at 600 rpm. Plus minus 2° is still within spec.
  1. Clean the timing marks.
  2. Connect the timing light's inductive pickup. - Place it over the #1 spark plug wire (front driver side) so the wire goes through the opening. -Route the wire so its clear of exhaust and the fan, belts, etc, and so you can hold the light pointing at the timing marks.
  3. Connect the tach/dwell meter if that's what you have for a tach.
Start the engine.
  1. If its not warmed up, get the engine warmed up.
  2. Kick it off fast idle. When it will run at slow idle (no choke), connect the timing light power. Most timing lights get power from the battery. Positve clamp to positive, the other one to negative.
  3. Remove the hose from the distributor's vacuum advance. Stick a golf tee in the hose. Alternatively, remove the distributor vacuum hose from the nipple on the carburator's side. Place a rubber cap over the nipple.
  4. Read the RPM and the Timing. Write them down
  5. Adjust the idle speed screw to change rpm and read the timing again. (write down how many 1/8 or 1/4 turns of the screw you make so you can go back if needed).
You should be able to measure and set the timing at 600 rpm.
If you can do that. Great!
If you want to check the mechanical advance is working, turn the idle speed screw in to bring the rpms up. Write down the new rpms and the new timing reading. Do this up to the top rpm of the tach/dwell - usually this is around 1200 rpm. If you have an dash tach and you want to measure at higher rpms, thats fine. When done measuring, return the idle speed screw to 600 rpm.

Reattach the distributor's vacuum hose to the vacuum port on the side of the carb.
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mymopar.com has a digital '66 FSM
manual transmission 2-bbl engines are 5*BTC
upload_2022-7-23_15-9-12.png


Idle rpm was 500 for the manual 2bbl
upload_2022-7-23_15-11-53.png


600 rpm with hi-perf package
upload_2022-7-23_15-13-15.png
 
Demonracer said:
Yes, unplug the vacuum line from the advance but be sure to plug the hose so you DO NOT have a vacuum leak.
Click to expand...
It shouldn't matter whether you plug the vacuum advance line or not. There should be no vacuum there at idle. If there is, you have a carb problem, or hoses connected incorrectly.
 
That's probably true with a factory mopar, without CAP, of this era.
However its always good practice to plug the distributor advance. On some setups there is a little bit of exposure of the vacuum port to manifold vacuum at idle. Also then its a good habit when dealing with vehciles that used manifold vacuum advance like an early 60s Kaiser Jeep.
 
cudamark said:
It shouldn't matter whether you plug the vacuum advance line or not. There should be no vacuum there at idle. If there is, you have a carb problem, or hoses connected incorrectly.
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I do have vacuum there at Idle, I will check the routing. Its a "new" (refurbished) carb.
 
Sellingthewind said:
I do have vacuum there at Idle, I will check the routing. Its a "new" (refurbished) carb.
Click to expand...


um, there should be vacuum and vacuum advance at idle, that is why you remove the hose to check timing. The vacuum should go away when you accelerate, if not this will cause your engine to stumble. If you reattach the vacuum line and your timing doesn't get more advanced at idle then you have a problem.
 
trapster said:
um, there should be vacuum and vacuum advance at idle, that is why you remove the hose to check timing. The vacuum should go away when you accelerate, if not this will cause your engine to stumble. If you reattach the vacuum line and your timing doesn't get more advanced at idle then you have a problem.
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Nope, it's the opposite. There should be no vacuum signal at idle. Just off idle the vacuum advance nipple gets vacuum as the throttle plates open. If it happened your way, you would have vacuum retard, not advance.
 
cudamark said:
Nope, it's the opposite. There should be no vacuum signal at idle. Just off idle the vacuum advance nipple gets vacuum as the throttle plates open. If it happened your way, you would have vacuum retard, not advance.
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Nope, but that is what I used to think also, the vacuum should be highest at idle.
A lean fuel charge burns slower so you need more spark advance, which is what happens when you have a lot of vacuum.




THere is no vacuum advance at WOT only at idle or cruising.
 
trapster said:
Nope, but that is what I used to think also, the vacuum should be highest at idle.
A lean fuel charge burns slower so you need more spark advance, which is what happens when you have a lot of vacuum.




THere is no vacuum advance at WOT only at idle or cruising.
Click to expand...

We're talking a street car here. He's not running the engine at WOT. Even at the initial WOT, you get vacuum advance until the manifold vacuum drops. At that point, the RPM's are up a bit and the mechanical advance takes over. If you ran your vacuum advance hose directly to the intake along with say 10 degrees of initial timing, you would have somewhere around 25-30 degrees combined at idle. Way too much and bound to ping on you. With using the proper ported vacuum outlet on the carb, initial stays at 10 degrees at idle, but, then advances as soon as you open the throttle. Sure, the vacuum will drop off if you stay in it, but, that doesn't last long in normal driving. On a drag car, or, an engine with a radical cam, you don't even use a vacuum advance, because you don't have enough vacuum to work one properly. Gas mileage will suffer without one, but, that's not a concern on a drag car. They just use a distributor with more mechanical advance range and slightly more initial timing. All it takes is for you to hook up a vacuum gauge with a T-fitting to the proper port on the carb, and watch the timing light as you work the throttle to see how that works.
 
The ported or "timed spark vacuum port" as Holley calls it has zero vacuum at idle. That's the whole meaning of "ported vacuum" versus "manifold vacuum". The only reason it is advised to disconnect and plug the vacuum advance hose is " just in case" the idle speed is high enough to actuate the vacuum advance can. Once timing is adjusted correctly and idle speed is correct, the vacuum advance will not make any difference whatsoever at idle. If it does, you do not have it connected to ported vacuum. Ported vacuum is generally any vacuum inlet above the throttle blades, but there are exceptions, that's why it's best to check with a vacuum gauge.

Now, if we are discussing connecting the vacuum advance to manifold vacuum, then completely different rules apply.
 
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