I have a 72 F100 w/ 390/c6. The truck starts ok when cold but after driving a while if I shut it off and then try to restart it the motor barely turns over (like the starter is dragging) if i try it again it will usually start. I believe this is actually a distributor problem w/ the vacum advance... the reason I think that is I loosened the dizzy and retarded it - the motor turned over normally. I retimed the truck and once again - will start ok when cold - but not when warm. I might add that this seems to be intermitant. Am I on the right track thinking this is a dizzy problem???

 

your adavance is to far. what is the base setting?

 

Does your truck start hot every time you retard the timing, or once in awhile? If it does it every time 390 is prob right, if it doesnt, I would look at some other things. Wire connections, solenoid, battery, starter, etc. I dont pay much attention to the timing marks on my 390. I have it set to where it doesnt knock or rattle when I step on it, seems like it will take more timing in the winter than the summer. If I go with higher octane gas in the summer, I can leave it the same.

 

If it only does it when it's hot, 99% of the time it's the starter. A dist. will not in any way affect cranking speed. The only thing too advanced would affect is if it's bucking the starter, it would have to be way out for that and you'd have to have at least 10:1 compression.
My timing is set at 16 degrees initial timing, max 36 degrees.

 

Well - I can't say for sure what the timing is set at since I time by ear and how well I can get the motor to run....if I run the truck for a few miles, then turn it off and try to start it again I get the slow starter drag. However, if I turn the ignition offf and try to start it again it will usually start. Thinking mayber the dizzy advances initially to start and then doesn't retard fully (faulty springs?)...but when I try to restart and it drags - if I twist the dizzy I can get it to start everytime. That is my confusion regarding the starter vs. the distributor timing. I would think that if it were the starter dragging 'cause it is hot that it would drag no matter what the timing was....I had the truck in the shop about 8 months ago and the truck was timed w/ a light....and it was fairly close. Truck has done this for a couple of years...just now pissing me off enough to track down the problem. It has never failed to start...this is my daily transportation and it has always been reliable (given the usual quirks).

 

I had the same problem and it ended up being that me engine ground was so coroded. I replaced it and it never did it again.

 

I have had this problem with many carbureted trucks, trying to get max power out of them. The problem is that the base timing is set to advanced, and since the fuel mix is being lit off that much sooner before TDC, the starter is having to fight it. I got around this on a couple of trucks by putting in an ignition kill switch, get it cranking at full speed, then flip the switch on. It would usually fire right up. One of the DSII boxes retards the timing while cranking, I can't remember which one it is, though.

 

Thanx for the replies - gives me a couple more things to consider. It is 20 degrees here this morning (and truck fired right up) - thinking I won't gat back on this problem 'till it warms up a bit.

 

Have you tried a different starter? If your wires are original, I would re-wire too. I once installed a rebuilt starter on my 390, and it was a bad one. (So much for lifetime guarantee). Anyone have one of those mini-starters (high torque) models on their truck?

 

The Duraspark II box with the blue connector retards the timing. It is supposed to be wired so that it retards only while cranking. If you wire that one wire up to full time juice, it will retard the timing from its base, and you'll have to advance the distributor accordingly.

Yes, this feature really works. Once I had it wired up correctly, my starter drag quit, because the slow cranking speed was fighting the over-advanced base timing.

Here is how you wire the Duraspark II up:

Distributor:
1 plug. Connects to the wiring harness which goes to the brain box and coil.

Coil:
The TACH wire comes from the brain box to the coil, but is not part of the distributor plug. Avoid cutting this wire during disassembly if at all possible.
The other wire, the BAT wire, will not go to the box, it will be the power supply for the coil. Connect this wire to the original points distributor wire. It usually is black (I think).

Brain box:
One 4-wire harness, to the coil and distributor.
One 2-wire plug. This one is what you need for the cranking retard function.
Red wire: 12V at Run, not at Start. This provides regular timing for the Run circuit.
White wire: 12V at Start only. This provides a few degrees of timing retard.

If you can harvest the entire system from a truck, you'll be much better off. Be sure to dissect the wires out from the harnesses, giving as much lead as possible to any wires you have to cut.

Hope this helps!