Converting a mallory distributor to flathead crab style


Well-known member
Mar 23, 2008
To convert a regular dual point, unilite or magnetic breakerless distributor to a flat cap/crab cap you will need the cap (mallory # 221)

However, you'll soon realize that the contacts inside the cap are placed on a larger diameter circle than the ordinary cap, so you will need:

Mallory # 318 Crab Style Mallory Flathead Rotor, 5/8" Shaft

This will fit the normal shaft, if for some reson you have the smaller shaft, they have one for that size also.

Then you will need to machine the distributor because the housing OD is larger than the cap ID.



After this is done, the cap will fit but the straps are way too long. You can then either fabricate some clamps or buy a strap kit. I have a set of fabricated clamps on there now, still waiting on the straps to get here.

The crab style cap gives a clean finish and a lot of added room there.
Nice... but I thought the purpose of this cap was to have the wires 1,3,5,7 and 2,4,6,8 on each side of the distributor. What's the advantage of this cap if you still cross the wires ?
That's called a crossfire cap, this is not the same. This is just to make the whole thing flatter and lower profile. Otherwise his carbon fiber airbox won't fit :) it uses 16" filter elements.
Xander, I also have a small cap, dual point, mech tach drive, Mallory dizzy. What ignition system did you use to upgrade? Thinking about doing that. I also was wondering about integrating a cam sync. It would be perfect for use on our older C3 cars for EFI upgrading.

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I use mallory products exclusivly, I dislike the MSD boxes, the mallory unit is so much nicer (I also like the crane box Marck is running with his boost retard setup which has the added bonus of weatherpack connectors). I have had 3 MSD boxes fail for no apparent reason, they are analog and draw more amps than the mallory, have a lower output and slowly drain the battery.

I have the mallory dizzy, mallory 6 ignition box and mallory pro master coil.
Oh, it's a magnetic breakerless distributor, a 57 series.

I also have an old dual point, several unilites and such..all different series. I didn't convert it but you CAN buy the other parts required to convert to either MBI or Unilite. You can get those parts from Mallory. They offer complete kits, listed on their site.

BTW, if you order a new distributor it'll cost 75$ to have it converted to the crab style cap by Mallory.

So you have a dual point w/ mech tach drive? I have an old YL-565HF here. The housing is different than the 57 series MBI. It's similar in size to a 37 series Unilite (3748201D) I have here. The housings have a ridge where the 57 does not, right where I machined mine for the other cap.
Here's the dual point, same style housing as the 37 series Unilite (except the unlite has a different style strap, the housing has cast ears but it's a very old piece).



The other unilite is this style, it must be a different series. This is the same style as the 57 MBI.

The old housings have that ridge at the top, all the newer ones are the smooth machined style.
So you have a dual point w/ mech tach drive?

Thanks V.....Yes I have a new, never installed Mallory model 2648201. (26 series) It has the ridge at the top of the housing so it must be the older style like your example. From what I have been able to find since your post, it will need a "Mallory 558 - Mallory Unilite Conversion Kit" to update to electronic breakerless.


Now, can this dizzy then be machined to handle the crab style cap with the above Unilite kit like your example?

I like the MBI conversion better, the unilite pickup can get dirty and behave erratic

Yes, the dizzy can be machined, however, I don't know if the unilite rotor with the shutter wheel is available for the flat cap so that's also a reason to go with the magnetic pickup