81 F100 flare side custom with 300 six & T18

The easiest thing I have done on the truck so far has to be adjust the dist. vacuum advance can.

I forgot I gave it 3 turns to start as the pinging was pretty bad.
Well after a good road test I only get a little pinging when in 4th gear pulling a hill RPM about 1000 and foot to the floor. If I hold it steady or just a little more throttle no pinging.
It still has good power from off idle on up the RPM range so I am going to call it good.
Dave ----

Watch it at just slightly more throttle than needed to cruise at maybe 45 MPH up. That’s because the advance will be greatest at the highest vacuum. At WOT there’s not much vacuum nor advance.

But glad it is getting g sorted that easily. 👍

Gary Lewis wrote

On the pinging, I'd bet it is because you aren't adding the exhaust gas.  So the mix is crisp and the burn rate fast, as opposed to the mix diluted with exhaust gas, which burns much more slowly.  So they dial in a lot of vacuum advance because it is under light load that the EGR kicks in.  And your test of plugging the vacuum line to see if the pinging stops is the right thing to do.

But you may already have an adjustable can.  Go in there with a really small Allen wrench, typically 3/32", and see if it engages in a screw head.  Crane says to turn the screw counterclockwise 2 turns at a time until the pinging goes away.

Gary, I had to go back in time to find this: 9/13/2014

 
Gary Lewis
 
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We played with David's truck today to determine what his AFR is and what his timing is. First, we installed my AEM wideband meter and looked at the AFR:
Idle: Once warmed up it was about 12.5:1
Cruise: At 62 where he ususally runs it was in the mid-15's on level ground, but climbing hills it got as high as 17.0 at one point.
Power: Once the throttle was open it went as low as 11.5 but normally at about 12.0 - 12.5.
That said the carb, a 1970 YF carb off of an F350, is jetted just right. It really shouldn't be any leaner, but the truck runs well so it isn't too lean. And it certainly isn't rich.

Then we checked the timing. The initial timing was set at 18 degrees, which was getting good MPG but made the engine slightly hard to start sometimes. And, it pinged at full throttle, so the overall timing was too much.

As for the mechanical timing, at 1700 RPM where David cruises it was giving 10 more degrees advance. Then we checked the vacuum advance and found that it was starting to advance at 10" and was giving a total of 18 degrees 16" of vacuum, and at the 14" of vacuum the truck had at 62 MPH the advance was 12 degrees. So, total advance at 1700 was 18+10+12=40.

Then we turned the vacuum advance two turns clockwise, which made the vacuum start coming in at 8", gave the full advance of 18 degees advance at 14". Then we set the initial timing to 17 degrees, and the drive determined that it pinged both at part throttle as well as full throttle. So we put the initial timing at 14+, giving a total of 14+10+18 = 42 degrees at 1700 RPM. And the truck felt happier with that setting than it has.

Good find, David!  And yes, if it pings at WOT there's either too much initial advance or too much centrifugal advance as there shouldn't be any vacuum advance.

But that info should give Dave a good starting point.  

Dave...sorry to hijack here, but I have a related question maybe you and others can help with?

I've been thinking about vacuum advance.

I have mine connected to the ported vacuum barb on my Holley carb, and I have confirmed that there is no vacuum present at idle. However, by barely moving the throttle off idle, I will quickly get full vacuum.

But, I don't want full vacuum applied to my vacuum advance immediately off idle, correct?

Is that vacuum only present because there's no load on the engine, and I'm just revving it?

Just trying to wrap my brain around that. I would assume that I wouldn't want full vacuum advance just off idle...but maybe the vacuum behaves differently when driving with a load on it?

Vacuum is dependant on throttle opening.

Hooking it to manifold vacuum (like Ford intended) gives you full vacuum advance at idle.
Hooking it to ported vacuum gives you no advance at idle, but full advance at cruise (small throttle opening)

Vacuum and centrifugal advance work in concert, because you'll never have 3,000 or more rpms and a tiny throttle opening.
You can more easily tune centrifugal advance with springs, stops, and the weights themselves, but it won't effect advance below a certain threshold, unless you use two incredibly light springs (and at that point you've defeated the purpose) just like locking the timing on a drag car.

If you want the vacuum to change more slowly use one of the vacuum restrictors that Ford installed in the line coming from the thermal vacuum switch.

It's a little orifice with a colored plastic 'flag' that fits in the hose.

I don't know what colors correspond to what size hole, but I do know they're different sizes.

Thanks guys for the information.
I was at about 45MPH when I went WOT on this hill and got just  little hint of pinging.
Before I made that can adjustment I would have pinging all the time at almost any speed even on flat ground.

Yes I should see what base timing is but it starts great, no kick back like to far advance and fires right off.
One day I will check all parts of the timing curve but I stopped the pinging, still have good power and that was the main goal to save the motor.

Cory, NP on the high jack as it may also help others if they do a search.
Dave ----

ArdWrknTrk wrote

Hooking it to manifold vacuum (like Ford intended) gives you full vacuum advance at idle.

I thought Ford was ported vacuum for distributor vacuum advance, no?

I thought full manifold vacuum for vacuum advance was a Chevy thing.

Have I been reading wrong all this time?>..lol.

And where do I get one of these restrictors? Can I buy a Ford one or a new aftermarket?

I've never seen anything but manifold vacuum on a DSII engine.
Check some of the many vacuum routing diagrams online.
Always red going to the thermal vacuum switch, then through that restrictor.
Except when the switch detects overheating.

I've kept mine from day one.
I'm sure you could scavenge one, or maybe Gary could get you the p/n's
I have the MPC on CD, but no device to read it ATM.

Cory - Jim is right.  Effectively the only difference between ported and manifold vacuum is that you don't have vacuum at idle.  Other than that there's essentially no difference.

The reason I like ported vacuum is that it gives a stable idle.  This is especially needed with an automatic.  With manifold vacuum when you start the engine and let it idle in neutral there is high vacuum so a lot of advance, which creates a high RPM.  Then you drop it in gear and the RPM drops, which drops the vacuum, which drops the advance, which reduces the RPM, which drops the vacuum, which....

But with your truck there's no big reason to go with ported over manifold vacuum since you have the manual transmission.

ArdWrknTrk wrote

I've never seen anything but manifold vacuum on a DSII engine.
Check some of the many vacuum routing diagrams online.
Always red going to the thermal vacuum switch, then through that restrictor.
Except when the switch detects overheating.

OK, gotcha. I was looking at my vacuum diagram on the truck, and it just shows a line straight from the carb to the vacuum advance. I don't remember what port it was on...the original 2bbl is long gone, but it was just a plastic line with short sections of rubber at each end. That was the factory piece at least.

I'll carry on then. I was just thinking of some things to do to get this set up when I get my distributor back.

Out of curiosity, what are these Ford "Check valves" for?

https://www.summitracing.com/parts/smp-dcv1

I can't understand how that would work if it actually IS a check valve.

I DO like the idea of a restrictor in the vacuum advance line. That would address my concerns perfectly.

Rembrant wrote

Out of curiosity, what are these Ford "Check valves" for?

https://www.summitracing.com/parts/smp-dcv1

I can't understand how that would work if it actually IS a check valve.

Never mind...I see it's actually a vacuum delay valve. Delay in one direction, full flow in the other.

Dave,

Sorry for the HIJACK!

Carry on folks, I'm good!

Rembrant wrote

I DO like the idea of a restrictor in the vacuum advance line. That would address my concerns perfectly.

Here you are, Cory. I have used one like this, before.

https://www.amazon.com/Dorman-Help-47311-Restrictor-X-0185/dp/B000CO7APW

When I got home from work I was surprised to see a box from Blue Top so if I don't have to work this weekend you know what I will be doing.
Dave ----

Hope you get to install it, and get to update us on the results.  

FuzzFace2 wrote

When I got home from work I was surprised to see a box from Blue Top so if I don't have to work this weekend you know what I will be doing.
Dave ----

I think an upgraded steering box is one of the most (or THEE most) valuable upgrades you can buy and install on these trucks. Congrats Dave. I'd swapped those boxes so many times now I'm sure I could do it all by feel. Keep us posted.

PS: If you still have the old C2 steering pump, be careful when you fill/burp it or you will end up with oil all over the floor like I did...lol.

Gary Lewis wrote

Cory - Jim is right.  Effectively the only difference between ported and manifold vacuum is that you don't have vacuum at idle.  Other than that there's essentially no difference.

The reason I like ported vacuum is that it gives a stable idle.  This is especially needed with an automatic.  With manifold vacuum when you start the engine and let it idle in neutral there is high vacuum so a lot of advance, which creates a high RPM.  Then you drop it in gear and the RPM drops, which drops the vacuum, which drops the advance, which reduces the RPM, which drops the vacuum, which....

But with your truck there's no big reason to go with ported over manifold vacuum since you have the manual transmission.

I was talking to Scott at Parkland last night. He has my new distributor all dialed in and will be shipping it out today. I can't wait to get it. I asked him my vacuum questions, and he said to absolutely use ported vacuum, and absolutely no to any kind of delay or restriction on the vacuum advance.

Depending on the weather, I may not have much opportunity to test this thing other than running it in my garage. Stupid winter!

Yes, the C2 pump will burb fluid everywhere.  

Glad Scotty is shipping your dizzy out today.  Maybe you can catch a break in the weather and test the truck out soon.