I have a 1970 F-100 Custom with a 300cid 6 (4 spd with X1 1st)
I was happy with the way my truck has been running since the YF rebuild and Exhaust manifold replacement. Timing was set as best I could (slightly off the mark seems to run better, slight "puff" at idle, needs more tune up parts), and points were burnt. I sanded them and set the gap. Truck ran great, except when at steady speed it will buck and exhaust pops a little. During downshifts now I am getting loud backfires, so no more Downshifting
Anyway I went to go replace the points (bought for a 1970 F100 300cid) and found that they are arranged opposite to what is in the distributor. So I think I may have a different distributor. Or once again the parts place pulled the wrong parts lol.
I have questions about this Dist. anyways. It has a diaphragm for the advance with two vacuum lines to it. Not sure which is for port and which is for manifold.
The part number on the dist is C8TF 12127 D date code: 0J11 It is also stamped AUTOLITE.

I do need to check my spark plugs too, may do that today...

I would much like to remove the dist. for a DIS with ignition module and coil pack. But I can't find one and very expensive if I did. The electronic deal to remove the points is a nice idea - still pricey. Thinking of going with Duraspark II - I love junkyard builds.
It is what it is. Thanks for your time.

 

Have you considered a pertronix ignition to replace the points? You can get it new for 80-90 dollars.

 

Port furtherest away from distributor is ported vacuum. Nearest to distributor is for manifold vacuum.

 

me, too.
Points to Electronic Ignition Cheap & Easy - ADVrider

i've never understood the dual-vacuum units. off idle, both ports have vacuum applied...how does that work to advance the spark?

 

Manifold vacuum is retard on these. As throttle is opened, manifold pressure drops and ported vacuum increases, advancing timing. Very few vehicles still have everything hooked up so the advance side is normally only one used. If fact, many people either leave the manifold vac disconnected or swap to a single port canister.

 

gfw1985 Thanks for clearing that up. I did notice that the replacement from Autozone is single action.

rustywheel68 I think I remember those being put on the inside of the front bumper of the T-birds, due to the heat they develop.

Turns out I got the wrong points ... was given a set for a 5.0

So getting the right points, checking plugs, double checking vacuum lines should shape things up.

Looking into a Duraspark setup. I like wires and I don't care for points. Hope to pick it up for half the price of Pertronix. Need to keep an eye out for 1/2 off weekend

Thanks for all your inputs

 

I hear people worry about the heat a lot. I've only got experience with the setup i'm running, so I can't say its not an issue. I've got mine mounted on the inside of my radiator support- it never even gets warm.

The Duraspark is a good setup, though- keep us posted.

 

So far so good. Got the right points, set gap .027. Went ahead and replaced the plugs with motorcraft, had autolite. Plugs gaped to .035, found the old ones under and over. Set timing 6° BTDC. Port vacuum to advance side, left the retard side open and plugged the manifold vac port.
First test drive went very well. smooth accel, no backfires on decel, and holds speed smooth!
Need to take it out on the freeway for a good run.
Will update with the duraspark swap happens. May not be till later this year.
Thanks again.