View Full Version : Distributor Question

08-30-2004, 10:01 AM
I just bought a new cap & rotor for my 88 PS 190 w/ 351. The old cap was black and the new one is tan. Also, the old and new rotors look slightly different. Having been through this with cars, I know that sometimes new and old parts look different just because thing have changed over the years. However, my owners manual specifies different timing settings for a tan and a black distributor cap. So my question is how do I know whether I have the wrong cap & rotor or if the design happened to change in the last few years?

08-30-2004, 01:41 PM
I just replaced my cap and rotor on my 88 PS as well, along with the electronic ignition -- which I really like. My new cap was tan and the old was black, and the new tan one installed and operated well.

After the change, my timing was still 10 degrees BTDC. It did not change with the install. Hope that helps.

08-30-2004, 02:11 PM
Hold the old cap over the new one and see if the plug wire towers line up with the hold-downs aligned. If they're slightly offset, the cap is different. The main difference with Ford caps is whether it's a screw down or clip down.

08-31-2004, 07:24 AM
That's what I was assuming, Jim, but would I be able to tell if the timing is different by just 6 degrees? I think the timing for the tan cap is 4 deg BTDC and the black is 10.

The other difference is the metal "spring" at the top of the rotor. on my old one, this is bent to contact the top of the cap (and provide some downward resistance, I assume). On the new one the metal piece is completely flat -- so again not sure if this is design change or not.

08-31-2004, 09:07 AM

Where did you purchase your replacement cap & rotor at? Mine were from DIM, and the rotor looked identical and I never checked to see if the towers lined up from the tan to the black.

As told to me, they are both exact OE replacments. Although the light didn't see a change from the old to the new, now you have me concerned that my timing should be set 4 deg :confused: !


08-31-2004, 11:29 AM
Where exactly is that head scratching guy anyway? :confused:

Dumb question... why would the cap change the deg BTDC of the timing? I understand having to turn it more or less if the polls don't line up... but - shouldn't the suggested spark advance be the same? If you're timing the distance before the cylinder hits top dead center to send the spark.... I just don't see how that would change. Like I said - I can understand having to turn the distributor more or less to achieve the same time - but not that the time itself would be any different.


08-31-2004, 12:02 PM
Good point, Jimmer. I'd think the spark timing would be unique to your engine / cam setup, not the distributor cap. Maybe the cap is just indicative of different internals in the engine when it originally comes from Indmar / Ford. Help me here, JimN. I know you have the answer....