Hi Guys,

I'm new here so please be gentle

Recently brought a lovely F100 1966 Ranger, FE 352. Manual 3 speed.

When I brought the truck it had a missfire, it was running way to rich (smelt of fuel and was puffing soot).

I got the beast home and booked it into a garage. They replaced the plugs, coil and installed a new carb and electronic ignition (got rid of the points), which mad a hell of a difference. The issue still exists when accelerating steadily, or when you hit a nice hill the truck would miss. The miss would not a big miss but you could feel the engine struggle. If I would put my foot down, give it some gas the engine would liven up and get up the hill without an issue.

I have changed the distributor cap, plug wires and changed the fuel filter. I have checked the spark plug gaps, checked the state of the new plugs to see how the engine is running. The plugs are a lovely clean color, not oily, chard or black. Everything look good.

I was wondering if it might be an issue with the vacuum can on the side of the distributor. I noticed on the distributor side of the vacuum pan (not sure what its called) there is a small hole. It looks like something should be in there? I have had a look around the new to see if i can grab a picture of the distributor to see if it should be plugged, anyone have any views on this?

I really want to get the engine purring and i believe I'm nearly there (hopefully). Any advice you guys can give will be greatly appreciated.

Will upload some pics of the truck soon

 

Anyone have a clue?

 

Just tossing ideas to see if they stick? Likely aware, with the EI upgrade believe plug gap runs around .044. Check the fuel bowl level, should come to the bottom of the screw opening. Suggest check the vacuum advance; depending upon type carb., usually need to block the vac. advance line when setting the timing. Not clear about comment 'hole on side of 'vacuum can', perhaps more knowledgeable member can offer suggestions, pic's may help? A change in timing requires going back and set idle mixture. If you have access to a vacuum gauge, find a primary vacuum source and should be running between 18-21. Upgraded to EI on the 65 w/ 390 and found on inline did not have enough power to blow out a candle, solved by resetting the timing? Anyhow, see with no comments thought I would add food for thought??

 

Welcome to FTE

Second the vacuum gauge, they are invaluable for troubleshooting, diagnostics and engine/carb tuning. This type of gauge is not the one that might typically be installed in the dash, but is a specific tool with a large, easy to read face. They are connected to a source of constant manifold vacuum. I don't know how anyone works on old iron without one. It will quickly eliminate several possible problems related to your issue, and troubleshooting is often just that. Anyway.

It sounds like your vacuum advance isn't hooked up. You want this to be hooked up, and will usually require a bit of tuning to make it right. That's probably why it's not hooked up in the first place - many people misunderstand both its purpose and function.

One type of intermittent or stumbling to check for is arcing to earth, either through the wires or, cross-firing at the distributor cap leads or boots. Check for this at night, or in a completely dark area at idle and look for sparks and listen for the "snap" they make whilst the engine stumbles.

Some say that spark plug gap is engine specific. In any event if there is an intermittent stumble, reducing spark plug gap back to .035" won't hurt a thing and would eliminate this as a source of the trouble.

If the plug gap is excessive for a given ignition, (or defective wires) the high tension will find an alternative path to earth. The whole idea is to make sure the plug gap is the only place voltage jumps back to earth ground

 

Little update. Went for a ride today after changing the rotor arm. Did around 120 miles in all, still missing when under load. Getting a timing light on it tomorrow to ensure that timing is set correctly.

 

I agree with direction Dave and Tedster are pointing you toward....

...Check your timing, ensure vacuum advance line is connected, use vacuum gauge below carb / at intake to to determine possible problems.

One thing not mentioned above that is worth checking out and that is the dampener timing marks. If you've got an original 40+ yr old harmonic dampener, it will have a rubber ring built into it that can get tired. If it does get tired, it can allow the timing marks to turn or move on the dampener. You'd need to determine #1 cylinder @ TDC to see if the timing marks have slid any on the old rubber. If the rubber is pushing out of the dampener, I'd suggest you look into replacing it.

What type of electronic ignition did they install for you?
Was it a Pertronix ignitor system into your old distributor?
Is the coil matched to the ignitor system?

Since you bought a new distributor cap, I'll assume you still have the old distributor. If it has been in service for many years, it may have seen better days and is wearing out. The advance plate mechanisms within the distributor pivot on pins that do wear out... even if the vacuum advance diaphragm is working as it should and is hooked up to a ported vacuum source (located on the side of the carb, above the base plate). The timing light may indicate erratic timing....a vacuum gauge would also indicate it.

Try to post a pic of the mystery hole at the vacuum can..... Are you missing one of the two screws that secures the vac can to the distributor?

What carb did they put on it for you?
Was it a 2-barrel Autolite 2100 or something else, such as a 2-barrel Holley?

Let us know what your timing light check tells you.......

BarnieTrk

 

Hi guy's,

A little update. Finally got a cheap timing light and vacuum gauge. Attached the vac to the header manifold (via the pipe running to the brake servo) and measured after the truck warmed up (have attached pic).

Checked the timing, and the initial reading was around 6 degrees. The previous owner had marked TDC and 10 degree increments on the pulley, i got up close with a light to confirm this was correct.

I also stripped the distributor to check that vacuum and weighted advance was in good order, no broken springs etc. I have also added a picture of the distributer stripped and the timing pulley with the marks on.










I played around with the timing, advanced it to 8 degrees and ran the truck down the road, wow what a difference. Still a minor hesitation but much more responsive. I came back and moved the timing to 10 degrees, and while I haven't ran it up the road yet I'm hopeful that the truck will purr like a kitten. I might need to alter the plug gap to stock if it's still playing around.

One thing I did notice is that the truck idles a lot nicer. Not jumping around like before.

Hopefully the nice cheap timing light has cracked the mystery, looks like vacuum is spot on

 

Outstanding. Now you will start to really understand how it all works together, and how an adjustment on one component interacts with another.

I use a smart phone, so it's tough to see but that type of distributor has weights that can be flipped, I think. Remember, distributor rotates at half the crank speed, so a 13L slot equals 26 degrees of mechanical advance on the damper. So the amount of total mechanical advance in the distributor is adjustable. More, or less.

Add to that figure whatever initial engine timing is - say 10 degrees, that's a total of 36 degrees BTDC. Finally, add another ten to fifteen degrees of vacuum advance and we reach roughly 50 degrees of engine timing advance when cruising steady down the highway.

You can tailor both the amount of advance either less or more initial but also WHEN during the RPM range for your application by installing lighter or heavier springs on the centrifugal weights. Usually limiting the mechanical advance, but installing lighter springs and increasing the initial timing is what works best for performance applications. This is basically opposite from stock factory settings.

Too much initial will cause starter kickback, though for example. What you want now is damper tape. They make it ready made or just measure around and divide by 36 and get 10 degree increments. Measure out to 50 BTDC. What you want to measure is how much, and when particularly the mechanical advance comes "all in" at a given RPM with vac advance disconnected.

If you're not hauling heavy loads, prior to 3000 RPM will be noticeably snappier. Generally all engines want as much advance as possible as early as possible, but this is not possible with either crap gasoline or when hauling a load of gravel. You may try increasing the initial advance to around 12 or 14 tho limiting the mechanical to the 10 slot. 34 to 36 degrees total. Also try advancing distributor for maximum vacuum at idle, till it starts to hunt or "wander" the idle speed. Then back off about 1" of indicated vacuum from there. See how that works, see what the light says too. Probably be about 12 degrees or so.

 

Hi Tedster9,

Will get some of the damper tape. Will take a little of the guess work out of the equation. I'm crossing my fingers that the run out tomorrow will be a dream at 10 degrees, and if it needs advancing a little more I will tweak it

Let's hope its nothing else

Is great to be able to work on something mechanical. I have a new VW California camper which I use as my DD. I wouldn't know where to start, and if I touched anything the CPU would complain that a sensor was disconnected etc. Great fun playing with real machines

 

Yep, see my edited post above. You may run out of "room" to advance the initial any farther without pinging unless and until the mechanical advance is dialed back a bit, shoot for around 34 total say.

 

Little update. Went for a run today and was running sweet at low speed, but when I got up to speed on a dual carriageway (around 65) I could feel the engine stumbling.

I had a look at the timing again, went up to 10 and back down to 8 but still running rough at low or high speed.

I did notice that the electronic ignition gap between the magnet and the electronic ignition unit made a difference to the timing. Bigger gap bigger change to timing. I guess that it takes longer for the pickup to notice the magnet etc. The electronic ignition is PerTronix Ignitor.

I have also noticed that the Holley carb installed by a local Yankee car garage might be set up slightly wrong. It has two needle valves that need to be kept at the same value. The left screw was around a quarter turn different from the right. I have set these both back at stock. Using a vacuum gauge to ensure everything is running good.

At idle the engine runs lovely. Rev the engine and it all sounds great. Under load it has the stumble at either low around 6 degrees and high speed at around 9 degrees.

Do you think if could be something else? PCV valve maybe? I did have a look at the PCV and noticed it rattles. No gauze or anything to stop oil getting in etc.

Next step, i'm going to set everything stock and work from there. What order should I work from? Timing or carb?

Any help greatly appreciated. I would love to get to the bottom of this

 

Did you ever hook up vacuum advance to the port on the carburetor?

When you get the damper marked you can observe the advance at idle and up to 3000 RPM or so using the timing light; with vac advance disconnected and plugged, and connected. Be careful, stay out of the plane of the spinning fan. Should see about 34 to 36 degrees by 3000 RPM W/ vac advance disconnected.

 

Yep connected the vac advance to the carb. When setting the timing I disconnect the vac, set the idle to around 8-9. Rev to 3k to check advance. It advances to around 26 without the vac and around 36 with the vac. Do you think this is correct?

I'm defiantly not getting 26 out of the mechanical advance.

I'm going to check float levels on the carb and set the plugs to the stock setting later to discount them from being the issue. Wanted to the let the engine cool before playing around with the plugs and fuel

 

One thing to check for is a slipped damper, due to age of the elastomeric between sections. This renders timing marks completely inaccurate. Common problem.

Usually 34 degrees or so total timing, initial + centrifugal is about right. Not including vacuum advance mind you. You may have to run it up pretty high in RPM to observe this with an OEM stock distributor: though.

Try this .Engine vacuum at idle should be 18-20" at sea level. Are you getting this?. Try advancing distributor clockwise at idle for highest possible steady reading, and then back off 1" from that figure. This is generally the optimum initial timing. Ignore timing light for this test.

Check for ping on acceleration, vac advance disconnected, back off a bit more if necessary. Reconnect vacuum advance, adjust as necessary. This is useful when damper is suspected to be defective. If this is the problem it will have to be replaced or repaired.

 

Hi Tedster9,

I'm getting 15 from the vacuum gauge, cant really squeeze anything more than that unless I advance the timing past 10.

What is ping you are talking about? What should I look for.

Do you think its worth advancing the timing to achieve 18-20 on the vac gauge and trying the truck down the road to see if it makes a difference?