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Discussion Starter · #1 ·
Hello All,

I believe I'm on the right track, but I would like to get the community's input. My 460 is going into an 83 F250 long bed with the 4 speed manual. It has a Comp K34-234 mild towing cam, an EGR delete, .040 over, deck is untouched, the stock iron heads have been faced .008 but not ported. Compression ratio is unknown but not far from stock. I was thinking about purchasing a recurved dizzy from Scotty (Hi Scotty) but I want to make sure that I understand what is happening in the distributor and why it would need alteration so I can do a better job of troubleshooting in the future. It's a Duraspark II(?) and when I went to pull it apart the shaft had what felt to be an egregious amount of side to side play. I pulled it apart anyway to familiarize myself with the internals, and then went and bought a re-man from the Napa (only place I could find that had one).

From what I understand, I'll want 10-12 degrees of initial, and 34-36 total advance without vacuum, which means I'll be looking for about 24 degrees of mechanical advance. Stock dizzy and the re-man both have the 16L/21L advance shaft fitted, but the stock dizzy had a little plastic bushing that was fitted over the stop pin. I did the math based on the formula from Scotty's recurve instructions, [Slot Width = (Degrees x .013) - Pin Width] and determined that the 16L slot with the pin bushed to .23 gives 23.69 degrees of mechanical advance. It would seem based on this that I am right in the neighborhood of where I want to be in terms of the mechanical advance.

I have the Mr. Gasket recurve springs in the mail, and will be swapping out the light spring and leaving the heavy spring stock to step the advance curve in an attempt to avoid too much advance under heavy loading. Based on the cam and the vehicle's intended use (street, hauling, towing, commuting) I believe that I am looking to have the mechanical advance all in by 3000. I haven't touched the vacuum dashpot yet but am aware that its advance will need to be dialed back due to the EGR delete. Would this be possible to calibrate on the bench with a vacuum pump or is it best left to be done when the engine is up and running?

Let me know if this line of reasoning sounds stable, or if there is something I may have overlooked or not considered.

T.P. Crockmier
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