Hi! haven't posted for some time but I always read the forum!

I run a 1987 F250 4X4 - 8800GVW with 100K+ miles; could be the 351HO engine, uncertain about the origin. The truck is a tank! I use it on the property for chores and trips for lumber, dump, garden, and gravel.

New Holley carb 700cfm - vacuum secondary
New Stealth Dual Plane manifold - no EGR or pollution pump
New dual exhaust; recent rebuild on C6 tranny & transfer case.

Right now I'm using a stock ford dizzy and a duraspark box with the blue grommet and yellow Accell coil (50KV). I'm following the conventional wiring diagram; power to white wire to start & bypass ballast resistor; power to red wire to run & resistor in series w/ coil.

If I set the timing to be able to start (approx 10 BTDC) truck runs weak - no power, can't climb a grade.
If I adjust the timing to run stronger, starting becomes a problem, lots of grunting and groaning!
I did all the obvious stuff - vacuum leaks, fuel pump and filter, plugs, wires, cap, rotor. Some plugs are oily - the engine is far from perfect!

I must have read hundreds of posts about this problem including dozens about recurving the ford dizzy.

I'm willing to try to recurve but I am uncertain about how much total advance and at what point in the rpm range. The engine rarely runs more than 3000 rpm, even at highway speeds under a load when I can get it moving.

I'm sorry to revisit this topic but your help is appreciated, regards, John

 

Sounds like you ignition isn't advancing, not sure about the earlier systems but does it have a spout plug you have to remove to set the timing? If so does the ignition begin to advance from base when the spout is plugged in?

 

Just a though. But I would check yer timing chain as follows. Remove the Dizzy cap so ya can see the rotor cap. Roll the engine back and forth by hand or with a wrench on the crank bolt. If the engine rolls over much at all from one way to the other before the rotor turns I would think the timing set is worn out.

 

One way to check to see the curv is, with the engine started, use a timeing light , and watch the marks advance as rpms are lifted. Note When you time it. The marks should stay pretty steady. Not alot of bouncing around. If bouncing around occurs, check bushing in distributer, check weights and springs.

I am not catching this, but did the engine run OK then one day you went to use it and walla the problem... or did you change something then the problem. What led upto this.

The duraspark ignition, while low on voltage is a reliable ignition. Check the obviouse ... grounds duraspark unit coil ect. What does your spark look like, at the coil and plugs. So many things Good Luck

 

Thanks for all the prompt replies.....

Paul O ... by spout are you referring to vacuum advance (retard) on the dizzy? When I rev the engine, no vacuum line, with the timing light, the timing mark moves. Mechanical advance?

Artic ... yes, there are several degrees of "slop" when I rotate the crank clockwise (cw) & ccw before the rotor moves ... how many degrees are reasonable for an "antique"?

Mustang .. you are close to the facts ... I was never satisfied with the "stock" setup that came with the engine. I purchased a Procomp knock-off HEI one-wire distro from ebay; it was junk; when I tried to reinstall the Ford stock setup, I can't seem to get it right!

I'm ready to go with any aftermarket product; any suggestions ? MSD ?

 

For your use, the stock Ford dizzy can be reworked/adjusted to do what you need. I have used the MSD boxes (6,6al) and found that on a stock engine, it is not worth the extra money over the durasparks. One problem (to me) was that the MSD will damn near fire water, so almost any idle/low speed mixture will burn, which is not good tuning. It sounds to me like the vacuum advance part is not working at all. Its all easy to check withour the engine running. With the engine running, you can tell the actual degrees each part is adding to the timing, but just to test function, you dont need the engine running.

Get one of those little pistol grip vacuum pumps sometimes used to bleed brake systems. Pull the cap, and put a vacuum with the pump on the vacuum canister on the dizzy. If its working, the arm to the top plate will pull in and hold. If it dosnt pull in or hold, the diaphram is leaking/ruptured. Next, grab the rotor button and try to turn it one way or the other. It wont turn one way, but will pull against the lower springs the other way and when released will snap back straight. That will test function of both vacuum and centrifugal.

Put the cap back on and leave the vacuum hose off the dizzy, but hook the vac pump to the cannister but do not pull vacuum. Crank the engine and notice where the timing is, rev the engine and see how many degrees it advances. let it idle back down, then pull vacuum with the pump and see where it goes to. That will test all the functionality. You could have a vacuum hose off somewhere, and the engine is not pulling enough manifold vacuum, that would be a problem. You may not have a one-way valve or a slow bleed valve (small plastic devices in the vacuum lines) hooked up right.

I will not go into all the different preferences of hooking up vacuum or dizzy tuning. That usually causes a long and generally contentious thread. I have my method and others have theirs. I personally like a lot of advance in very quickly, expecially on low-comp smog engines. It does wonders for the seat of the pants feel. The trick (s) are to keep timing low on the crank for ease of cranking, once cranked, time the he** out of it. When towing (low vacuum) or at higher speeds, advance cannot be too high (~38-40 deg) or you get pinging etc. Check the power valve to make sure its good and doesnt open too early (too low a vacuum), contrary to popular belief, rich mixtures are much easier to ignite (pre ignition or spark knock/pinging). There is also a decision that can be made about manifold vacuum or timed/spark port vacuum. My preference is manifold vacuum, but a lot of others like the timed/spark port source which appears as a port on the carb. That subject can really take off . Unless you have really torn into the hoses etc. might be best to just use the vacuum diagram under the hood.

Thats my .02, lets see what you get from someone else! LOL

 

benshere .... thanks for the reply....

On this engine, how much is too much? Certainly less than 40 deg!? I've always used ported vacuum; I felt direct mani vac brought too much too soon. Efficiency is less of a consideration. I rarely drive more than 300 miles per month. The carb & mani have been replaced; the smog setup was gone long ago; so, the existing vacuum diagram under the hood is less helpful.

Under load, at say 2500 rpm, how much advance is expected or normal or desirable for the windsor?

BTW, engine seems to run cold, less than 170 deg; how much does that affect the timing, pinging, etc. Remember, no smog stuff, so no thermal vac valves.

Best regards, John.

 

If it is a heavy load, so that manifold vacuum is very low, you wont have much if any effective vacuum, so therefore no vacuum advance pulled in. BTW, you may already be aware that manifold vacuum and ported vacuum are only different when the butterflies are fully seated. When the butterflies are pulled off seat just a tiny amout, both are the same. My preference is to run as much advance (on the crank and centrifugal) at 2500 as it will tolerate without pinging, and leave a slight safety margin, in case you get some really bad gas.

My preference is (may not work for your combination, but gives you an idea of what I am talking about) to put initial at a conservative amount ~10-12 deg, for easier cranking. Then, put light weight springs in the dizzy so you can get ~20 deg by 2500 on the centrifugal, that gives ~32-34 maybe more at that speed. Mid 30's to ~38 degrees is supposedly the power setting w/o vacuum. You may not be able to run that kind of advance for numerous reasons, but I would start there and see how it does. With that kind of advance, you will certainly have to limit any vacuum added in at "no load" to ~8-10 degrees, and that is greatly variable, depending upon lots of conditions. I have never played with a 351 carbed engine, so I am only speculating and hopefully giving you some idea as a starting point. It is probably the later electronics, so someone has mentioned that the "spout" plug will have to be pulled. Now that I think about it more, if you have an earlier dizzy with advance features a part of it, you may have a big problem in that the PCM may be trying to control advance in addition to the dizzy. That could be a big problem. Since that C6 (I think you said thats what it is) is not controlled by the PCM, and you arent FI, you may just have to run the engine as a pre-86. Maybe I have really confused things---hope not . I am sure you will get some good help from others.

I am not sure, but guessing that your H.O. carbed engine may be out of an 85, or the intake has been swapped from one. I believe that in the broncos, the carb was dropped in 85, but dont know what they did in the other truck lines. Again, LOL

 

Benshere Opened up ford dizzy, mechanical advance has two ears (13 and 18) currently set for 18. with my initial timing at 10 degrees that provides a total advance of 46 degrees with no vacuum. Springs appear to be one heavy and one medium. doing to switch to the 13 setting and will reinstall. shall post results when done. thank you.

 

Those old ford dizzys usually didnt fully advance until way up in rpm. With careful work, you could plan the curve at any rpm, but if you went over that in rpm, your curve would advance even more. Again, my preference was (is) to build the cent advance all in with the amount of degrees you wanted, all in fairly early, thereby taking any variation due to rpm out of the equation. You can also take some degrees off the centrifugal by putting the post in the 13 (26 deg crank) slot and slip a piece of vacuum hose over the post to limit its travel even further and taylor the advance to suit you. For example, if you want the crank at ~15 degrees, you would need to adjust the slot to ~12 degrees for the 38 degrees total. These figures are not absolutes, they will vary with your setup, but you get the idea.

On my van, I put a little roll pin, vertically, in the arm going to the plate for the vacuum advance by drilling a small hole in it so it limited vacuum pull-in to about 1/2 the amount of advance it normally pulled in. The roll pin would hit at the slot on the side of the dizzy into the canister and stop the travel of that arm. You could even adjust that further by adding small shims to the side at the opening. Basically, these small, CHEEP, things would give infinite adjustability. Sounds like you are into it, so you will be able to see what you need.
Again LOL

 

benshere .... so ... I reset max mech advance to 13 X 2 for 26 deg plus 10 deg initial advance and engine runs much better uphill under load. took your advice and used mani vac port for distro vac advance. not much change but no worse; i'll leave this setup and mess with the carb settings a little to tweak it up! Thanks for your help 36 deg all in at about 2800 rpm seems to be a comfort zone for the engine. Regards,,,,,

 

Now that its driveable and functioning, you can play with different settings to see how it runs. Did I mention that I used to like to put light springs in the advance so it would come in early? Anyway, sure is a lot easier on you when they run 1/2 way decent!!
Sounds great!

 

[quote=F250duke;7759378]Thanks for all the prompt replies.....

Paul O ... by spout are you referring to vacuum advance (retard) on the dizzy? When I rev the engine, no vacuum line, with the timing light, the timing mark moves. Mechanical advance?

Artic ... yes, there are several degrees of "slop" when I rotate the crank clockwise (cw) & ccw before the rotor moves ... how many degrees are reasonable for an "antique"?

Mustang .. you are close to the facts ... I was never satisfied with the "stock" setup that came with the engine. I purchased a Procomp knock-off HEI one-wire distro from ebay; it was junk; when I tried to reinstall the Ford stock setup, I can't seem to get it right!

We specialize in custom advance curves and we have build much higher
quality distributors than the e-bay units.

If you decide to get a new distributor, consider our custom curved Duraspark Distributor built with our new Full Length Oil Impregnated Bronze Bushing. The full length bushing improves timing stability and spark scatter. If stock appearance is not an issue, take a look at our one piece D.U.I. Distributor. Whether you choose the Duraspark or the D.U.I., we curve each on a distributor machine based on your engine combination. Please see them at:

http://performancedistributors.com/forddistributors.htm

Also, there is now an excellent installation article on the D.U.I. Distributor on the Ford-Trucks.com site at:

https://www.ford-trucks.com/article/idx/0/358/article/DUI_Ignition_Installation_In_A_Ford_351W_V8.html

Ignition Lesson of the Month: Hystereses, the difference between the timing as the rpm and vacuum increases to the timing as rpm and vacuum decrease, needs to be kept to a minimum. A precise advance curve accomplishes this.