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Hi all,

I want to replace the distributor by a Duraspark , is there a problem to use a small cap wit male connectors ?

because the space from distributor and firewall , and I want to use my original engine center cover.

and witch cable set is the best to use ? dont will cross the valve covers

any advice is welcome.


Last edited by simon
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I am using a Duraspark distributor with an MSD 6A box.

The distributor has an old school, black small diameter cap and uses male wire connectors plugging into distributor female sockets.  

I am using a Taylor 8mm “universal” silicone wire kit, with wiring cut to my desired lengths with correctly crimped terminals  

I have an early full screen center cover and the distributor poses no interference.

I have read where some say the smaller cap, with closer connections, can sometimes crossfire due to the high voltages in a modern ignition.

after about 3000 miles with this set up I have noticed no issues.


Hi Simon. Yes- using the small distributor cap is a good idea- indeed, it's the only cap that will fit an unaltered engine. All known big caps, stock or aftermarket WILL hit the firewall. And even if you fiddle with it and find a spot where you have maybe 1mm of clearance, the engine moves around more than that in its motor mounts under full acceleration. The cap bumps something solid and moves against the spring clips that hold it down, and the very next thing that happens is, the rotor breaks and the engine quits! I used to actually carry a spare cap & rotor in our Pantera for the occasional rescue on the road.

Its easy to shift the entire engine & ZF backwards 3/8"-1/2" for more distributor cap clearance, but many owners just are not able to do this. For them, a small cap with new wires is the practical solution. FWIW, a 1/2" move is the max I recommend because that small amount snuggles the back of the oil pan sump very close to the rear crossmember under the ZF. Trying to go further back puts you into a whole pile of other things that will now interfere. There are illustrated articles on this subject in the POCA Archives, with our car as an example from the '90s.

comparo 2

Standard Motor Products (SMP) part numbers

4 inch International Harvester (IHC) Cap with Male Terminals:  SMP# AL-482

Rotor for Ford Distributor & 4 inch cap:  SMP# FD-115

Heavy duty 351M/400 8.5mm ignition wire set:  SMP# 69404

The wire set includes female coil to male distributor cap wires in 2 different lengths, and one long male coil to male distributor cap wire.


I think this is what you're looking for. The wires are long enough for the 351M &  400, which is a little longer than 351C wires. I don't understand how you plan to route them, so I don't know if they are long enough for your intentions.

There shall be no problem with cross-firing caused by the smaller diameter cap as long as the engine is in a good state of tune, and the plugs and ignition wires are in good condition. The ignition shall only “cross-fire” when doing so provides a path to ground that is easier to travel than following the proper path to ground would be.

These ignitions were designed to ignite some very lean air/fuel mixtures diluted with exhaust gas (EGR); thus both Ford and GM engineers encountered cross-firing with the 4-inch cap. However, if your engine is equipped with a carburetor or fuel injection system providing a better air/fuel mixture the likelihood for cross-firing is reduced. I hope that makes sense.



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Last edited by George P

Simon, you may have noticed that posters do not necessarily use their proper names here but use a nickname or 'handle'. Back when the PI (paper) magazine existed and Dave & Linda Adler owned it and this web site, I used to write exclusive Tech articles for them as well as for POCA.  Dave Adler made up that 'Bosswrench' handle and the cartoon figure that went with it  way back in the mid-'80s, as a fun thing. When George took over the site, he simply continued the tradition. I'm not heavy-set like the figurine and wear glasses much of the time, but I DO own a really big wrench!

I recently upgraded to a Duraspark I system with a DUI rebuilt distributor. I installed the small cap and it seems to work fine. I've put about 80 miles on the car since the upgrade and zero problems. All i Can say is the Duraspark is one of the best upgrades I've done! See attached pic of small car lurking behind vent line.



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Last edited by George P

Hi George.  In this discussion you mentioned these parts:

"Standard Motor Products (SMP) part numbers

- 4 inch International Harvester (IHC) Cap with Male Terminals: SMP# AL-482

- Rotor for Ford Distributor & 4 inch cap: SMP# FD-115"

I can find the distributor cap at retail auto parts stores but the rotor (SMP # FD-115) only shows up on eBay.  Even the SMP site doesn't list it anymore.  Do you, or anyone else, happen to know what the replacement SMP part number might be for the rotor?

Thanks, Mike

George and all....nevermind.  I see I asked the same question years ago and George answered "I purchased the rotor via eBay circa August 2018.

I like using eBay because I can acquire SMP brand parts that way. There are no independent auto parts retailers locally here in Ventura, only chain outlets like O'Reilly, AutoZone, NAPA, and CarQuest. I have been burned by each of them. I've never been burned by an independent retailer selling SMP parts.

(SMP = Standard Motor Products)"

I just got one on order from eBay as well since I'm finally getting around to this project : )   Mike

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