What has been done to my 71 280 sel. The crank (timming marks), cam and injection pump are all aligned at proper specs.
The distributor does not line up at the proper specs in relation to the timing marks. For the longest time the idle timing was 21 degrees ATC not 8 ATC. Last week I replaced the front crank seal and rebuilt the distributor ( it was extremely dirty, rusty and grimy). The rebuild was perfect.
On reassembly I made sure everything was properly aligned. I started at 8 degrees and she started up but ran very rough so I adjusted her up to about 12 degrees and she ran better. On a road test I fine tuned the timing and she ran beautifully at highway speed (15 degrees).
Here is my problem. At a full stop in gear and with the A/C on she will stall when I apply gas. If I retard the timing so she does not stall, then I have pinging and power lose at highway speeds. I cannot find a happy middle ground.
Is there something which I am missing. I would appreciate any and all suggestions.

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Britton McIntyre

68 280 SE coupe 'Hairball'
70 280 SL
71 280 SEL - RIP May 2010

It sounds like your mechanical advance is not kicking in. This could be due to one of two things:
1) You made the springs for the mechanical advance too loose, so it goes full advance (or near it) @ idle when you set the timing
2) You made the springs too tight, so it never advances the timing at highway RPMs and therefore it's too late and your gas pre-ignites before it actually is set off by the far-too-latent timing.

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Current:
2021 Charger Scat Pack Widebody "Sinabee"
2018 Durango R/T

Previous:
1972 280SE 4.5
2014 Jeep Grand Cherokee Limited "Hefe", 1992 Jeep Cherokee Laredo "Jeepy", 2006 Charger R/T "Hemi"
1999 Chrysler 300M - RIP @ 221k

Do you mean the two springs one the weights and how do you adjust the advance? I did put a new vacuum unit on the distributor.

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Britton McIntyre

68 280 SE coupe 'Hairball'
70 280 SL
71 280 SEL - RIP May 2010

Take the cap off and turn the rotor by hand...does it snap back when you let go ???

..and does the vac element have 1 or 2 ports?

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A Dalton

It snaps back nicely and there is just one port.
After reading the manual and looking at how the advance is adjusted. I realized that I made a mistake with it. The slots on each side where the screws would attach to the housing are in the wrong position. I drilled holes on each side and attached it. I did not realize that the slots were there for adjustment. So I cut out slots and then played with how the adjustment worked.
After a few try's the engine is running better but when it is running over 80 mph there is pinging. I slightly advanced the timing and had problems at the low end. I returned the distributor to the previous position and drove home. The engine output is good but the pinging (a small amount) is robbing a little off the top end.
At this point how do I adjust the advance? Do I turn it pull it clockwise or counter?
*NOTE should I have replaced the small springs on the weights?

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Britton McIntyre

68 280 SE coupe 'Hairball'
70 280 SL
71 280 SEL - RIP May 2010

What is the dist number ??

I do not know why you would have to drill anything.

The MFI systems call for 30 degrees BTDC @ 3000 rpm.

That is where you should start w/o and vac going to the dist diaphragm
Then see what you have @ idle w/o vac. That should be A few degrees BTDC. Once you hook up the vac hose , then the timing shouid go to 8ATDC..the system is a vac RETARD system @ idle.

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A Dalton

On each side of the advance mounting brackets are two parallel slots. To line up the screw holes on the distributor to the advance required moving it up or down. When down the advance arm pushes down on the plate and up it hits the top of the distributor. This is why I cut the holes in between the original holes. Which is how the original advance was.
When I purchased the advance (Classic Mercedes) I used the engine number.

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Britton McIntyre

68 280 SE coupe 'Hairball'
70 280 SL
71 280 SEL - RIP May 2010

You want the dist number.

The dist only has a mechanical advance...the vac element you are talking about is not advance ..it is Retard...it retards the spark at idle .
So, you set the mechanical advance first at 30 BTDC @ 30000 rpm w/o vac.
Can you do that?

Does the daiphragm you bought have a screw adjustment on the length of the arm/rod ??

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A Dalton

Do this simple test and post the results.

At idle, engine up to temp...pull the vac line off the vac diaphragm.

The engine should speed up ...does it????

Return the vac line..the engine should return to normal idle speed ...does it ???

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A Dalton

I will do the test in the morning. I can not remember if I have done this test.
Sorry about the miss use of terminology. I am always mixing up stuff like that. Is mechanical advance the act of rotating the distributor clockwise (advance) or counter (retard)? If yes, then I can do that.

(On each side of the advance mounting brackets are two parallel slots. To line up the screw holes on the distributor to the advance required moving it up or down. When down the advance arm pushes down on the plate and up it hits the top of the distributor. This is why I cut the holes in between the original holes. Which is how the original advance was.
When I purchased the advance (Classic Mercedes) I used the engine number. )

In this post I was talking about the vacuum unit.
I will need to purchase a RPM meter that goes up 3000. My current unit only reads up too 2500.
The vacuum unit does not have a screw adjustment on the arm which is why I drilled the slots on the mounting. I can move the arm by loosing the screw on the side on the vacuum bracket.
The distributor number is 0 231 116 061

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Britton McIntyre

68 280 SE coupe 'Hairball'
70 280 SL
71 280 SEL - RIP May 2010

OK
That is the later dist.

The main point is to set the timing at 3K rpm or higher to 30 degrees. That is the max advance from the springs and the max advance spec that car wants. You don't need an RPM meter to do that , just get it to 30 and no further, no matter how high the rpms go.. You change that by turning the dist body by loosening the lock bolt.

Once you have 30, you then want to see what you have at idle w/o vac...that will tell you if the springs are bringing the mechanical advance back to normal. Then you add the vac hose and THAT RETARDS the dist to bring you down to 8 ATDC, They only want ATDC at idle..as soon as you open the throttle plate , that vac drops right off and the timing will jump into the BTDC range...[ that is what that test is all about]
Don't confuse ATDC and BTDC ...B is advanced ignition and A is retarded ignition.

Looking at the damper . to the left of zero is BTDC and to the right is ATDC..

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A Dalton

I understand the ATDC and BTDC fairly well. When I rebuild the head last summer. I must have read the manual 100 times to make sure I got it right and I was still nervous about the whole process.
The manual states 25-30. Pacific Fuel Injection sent me detailed instuctions (on how to set the timing and all the different settings) when they rebuildt the injection pump.
They did a great job and when called. They were more than happy answer my questions and help me with a problem.
So, I will rev it up high and set the timing at 30 ATDC w/o vac. I will do that in the morning and let you know how it turned out.
Thanks
Arthur
I always enjoy reading your post.

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Britton McIntyre

68 280 SE coupe 'Hairball'
70 280 SL
71 280 SEL - RIP May 2010

Yes ...25-30 is spec, that is why I don't want you to go past 30....That car will run on reg fuel if you bring it down to 25, but I like them at 30 for performance .
I also like the idle w/vac to not be so retarded, but that is up to you...they did that for early emmisions. I run them at @2 -4 ATDC @ idle w/vac. That gives you a much smoother running when the FI pump changes ranges from idle to low range on the governor. It also gives you a much better engine vac reading all around.
If you have a ping at 30, I recommend changing octane rather than retarding down towards the 25...again..up to you.
You will know you are close on the vac box setting b/c you will see that 300 rpm change when you do that idle vac hose removal test I mentioned.
That confirms instant advance when the vac box is taken out of the picture.
Timing lamp will show all those changes an you can then tweak it anyway you want, just do not move the dist body after getting that 30 set.
You can also change the lower end of the advance by bending the spring mounts, but as long as the strobe looks good at 1500, I would not play with that either..you just want to know that all is working under there ..and I suspect it is b/c you did the rotor snap back test I mentioned.
One last test to confirm that the throttle plate is completely closing:
Take the rubber cuff off the front of intake and when car is at idle and warmed up, cover that intake with a piece of cardboard..if the engine looses rpms, the throttle plate is not closing all the way at idle b/c someone has made the idle adjustment with the throttle stop set screw..a big mistake..that throttle plate has to be closed all the way at idle or the va box on the dist will not get the correct vac spec to pull the retard all the way to ATDC. All idle adjustments on that chassis are done with the air bleed screw and the FI pump thumb wheel knob...NEVER with the idle stop screw at the the throttle plate. This cardboard test is my own quicky test to confirm the plate is closed..the rpms should not change with or without the cardboard blocking the intake throat b/c the a/f mix does not come from there at idle...and at idle , the intake has it's max vac b/c the throttle plate is completely closed and the vac port is BEHIND the plate.
Read it twice and it will make sense.........

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A Dalton

You know, I started to think if I had not done the snap back test. I just did it and the rotor does snap back.
What does this mean and how do I fix it?
I have not seen this in the manual.

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Britton McIntyre

68 280 SE coupe 'Hairball'
70 280 SL
71 280 SEL - RIP May 2010

That is just another of my quicky test...if it did not snap back , you know the springs under the plate for the mechanical advance are broken or loose...turning the rotor is simply moving the advance plate against the springs..and the snap back is confirmation the spring are bringing it back...just a test we do to save time diagnosing advance problems.

You pass that test.

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A Dalton