82 F100 inline 6 - 92k miles
Engine is desmogged. Runs great but pings at low rpm acceleration. I have moved timing around 6-10 degrees but still pings regardless of timing. I removed and plugged distributor vacuum line and it quit pinging! I read that I should install an adjustable vacuum canister on the distributor. What do you advise? Thank you!

 

I bet if you check your vacuum canister is adjustable, my 81 was.
I wanted to replace it when I was messing with the weight springs but the first was not even for my distributor and the 2nd was not adjustable so I kept mine.


When you say lower RPM at what RPM, MPH and gear are you in? What transmission, rear gear ratio and size tires.
I also get a little pinging but I found running higher octan fuel helps a lot.
Mine when running reg. gas will ping at 1200 RPM @ 45 MPH when I start up a little hill.
If I do 50 MPH / 1300 RPM or better 55 MPH / 1400 RPM I dont get the pinging as much.
If I drop out of over drive on the same hill no pinging at all, 45 MPH / 1500 RPM, 50 MPH / 1700 RPM or better 55 MPH / 1800 RPM.

Now you should know the adjustment only changes at what HG the advance starts it does not limit how much and that is what you really need to do.
I did not know this when I had the distributor out or I would have looked closer at ho to limit the vacuum advance total.
It is what I have found you may find something different.
Dave ----

 

So every Ford distributor I've seen has two positions to determine total advance. Many times that can be higher than one thinks, like up into the 40's. If you are inclined to do some open heart surgery on your distributor, you can see which it is at, typically there will be an 18° slot and a 13 give or take(IIRC). The slots are marked. If on the 18° slot, try the lower number, you don't want to go the other way. This is a free change, just need some time. Most V8's are good with about 30 - 34 total advance, I would guess a 6 banger is no different. So hypothetically you have say 10° initial, and your distributor is setup on the 18 slot, that's 36° crank degrees, plus the initial 10° and you're at 46° total. That's too much folks.

Maybe this will help...everyone. I hope the link works.
https://docs.google.com/document/d/1...?pli=1&tab=t.0

 

I don't have a tach so can't provide actual rpms.... pinging mainly when normally accelerating in 3rd (no overdrive) and of course when encountering a hill. My C6 seems to shift into 3rd very early although every c6 I've had behaves this way. PLEASE TELL ME HOW TO DETERMINE IF MY VACUUM CANISTER IS ADJUSTABLE!. I stuck a Allen wrench thru the nipple and it went in about 1.5" and didn't feel a Allen screw? Thanks for the very informative 2 posts!

 

 

Pro are you sure that is not for the weights as I remember something like that for them but not the vacuum advance side. I also dont remember looking at this and should pull the distributor to check it out and see. I think if I could limit the weights and let the vacuum do it's thing would work but only testing will tell.

It takes a pretty small wrench and can be hard to get it in the screw. Then again this was on my 300 and I hear most if not all are adjustable unless some changed it out at some time?
I cant remember what the size is but when it warms up I will see if I can find the size. It is SAE size not metric.
Dave ----

 

Was hoping there was an Allen screw in nipple but just checked closer and no luck feeling anything in there. Never removed the canister before but might try to put in the other setting. REMEMBER... just desmogged everything and it wasn't pinging before desmog. Thanks much

 

They say if the EGR was working it cools the cylinder temps and helps to stop pinging so maybe that is why?
I never drove my truck when I bought it. Made sure the motor compression was good and ran on all 6 then pulled the truck apart for a 4 year cab off frame rebuild.
So when it got back on the road it was all new to me and had a lot of adjusting to do.

Now that I got my garage back, son moved his crap out, and it warms up a little I can get the truck in to look into more to get the pinging to stop on mine.
Dave ----

 

Wish I could read the first 2 lines on the paper to know what it says.
Again that adjustment only adds or removes tension on the spring and that will change at what HG (vacuum) the advance will start to move and add advance timing not limit it.
Just numbers: Less sprig it can start at 5 HG more spring it may not start till say 12 HG
You can test this with a hand vacuum pump with a gauge and watch the arm when it moves.
Dave ----

 

Yes. The weights simply cam the advance, the slots limit the advance. I found the another issue is the factory springs are typically too stiff and won't allow mechanical advance soon enough. I'm off in the weeds here...simply said, there are several adjustments to a distributor, some more effective than others.
Here's my distributor...
I'm set on the 10° slot


I might even know someone who has previously welded those slots to a very specific size to nail down their advance.

 

That is for the weight limit not the vacuum limit I think you said in another post up the page.
I knew of that limit and like a dummy did not check what slot mine is in

I really need to get back inside the distributor and check what all I got going on because when I was in there I was trying to stop the pinging and did not look at any of that.
I may have even added heaver springs to stop the pining?
I took notes when plotting the curve but I cant remember if I listed the springs I used?
Also part of the problem was no one makes a spring kit for the 300 six that I could find.
I cant remember what kit I went with, maybe in notes? I should dig them out and check. It is also getting warmer so can work in the non-heated garage again.
Dave ----

EDIT: Maybe I miss understood what you were saying in that other post (I just went back over it again) as we were talking about vacuum advance and you posted about the limit for the weights.
I know about the limit and on some distributors it has a post and you can use vacuum hose to close up the limit amount just like the welding would do in this case.
We are good

 

- THE ALLEN WRENCH SIZE ON FORD WAS 1/8in PER INST SHEET -
This period VAC ADV was a one-fit-all as the diaphragms were calibrated to each engine emissions calibration and FORD released this service replacement style to fit most all applications (as was also done with EGR VALVES of the period). There are also aftermarket diaphrams (HP) to control vacuum advance but one would assume the DIST mechanical curve is pre-EGR.

First (IMO), you need to check manifold vacuum with a gauge to see if the engine is running lean due to a possible vacuum leak. A dial-back timing light would also help.

2nd, we need to know how the engine was de-smogged and exactly what was removed.

Seeing as how the DIST was calibrated for EGR and a lean fuel trim, the DIST should be setup on a DIST MACHINE as to pre-1973 curve(s). Even IMCO (1968/ ) can throw the engine off if de-smogged). While I am thinking about it, EGR engines used a timing set to retard DIST IGN timing (initial). You might want to install a pre-1973 timing set. The fuel trim may also be too lean.

The correct setting for the vacuum advance would be done with a manometer at the same time as re curved or it can be adjusted in the field.

 

For some reason I thought the 1/8 wrench was too big but it has been a bit since I messed with the distributor.
I run a AFR gauge and the carb is set up a little on the lean side for the most part but when it pings it is on the rich side so I dont think it is a lean ping at that point.
Mine really only pings when the RPM is too low for load on the motor like pulling the 20' trailer and dropping half a gear, I have a range splitter over drive, puts the RPM a little to high for my liking.

When I get a few of my other projects out of the way I will get back on this to see what I can do get the power I want without the pinging but for now running higher octan gas is working.
Dave ----

 

Oh boy. This discussion is getting over my head. I wish I could talk on you guys level. Thx for the posts! I just checked a 1/8" allen wrench and it does seem to fit into an adjusting screw. At first I was using 3/32" and that was the problem. Now I'll start by turning clockwise to tighten the springs which might remedy the Pinging. Am I on the right track? Thanks again

 

- SEE IF THIS HELPS - SOURCE - https://engineerfix.com/how-to-adjus...e-distributor/

Now you have to adjust it while road testing as the vacuum source has to be under load. You drive it and if it pings, stop and back it off. Reverse turn direction for quicker cut-in.

Get back if any problem(s).