Mallory crab distributor, pros and cons on a 276 street engine?

[danliveshere]

Guys my Motor city flatheads engine , approximately 276 cubes, has a Mallory crab distributor on it. The engine was running rough and now won’t start and this afternoon I noticed some of the contacts in the cap are worn out( looks like the rotor button was touching a few on one side of the cap) and the other side look hardly touched. This is still a new build but hasn’t been on the road properly yet apart from a few miles last week, and it drove terribly. I guess my question is stick with this Mallory or rebuild a crab with points? There’s no vacuum advance to the Mallory, and I’d have to drill and tap the thickstun twin carb manifold to get a vacuum port, also how does the Mallory work without vacuum port? Is it just a race distributor or will it work ok on the street? Thanks Dan

[petehoovie]

Originally Posted by danliveshere

Guys my Motor city flatheads engine , approximately 276 cubes, has a Mallory crab distributor on it. The engine was running rough and now won’t start and this afternoon I noticed some of the contacts in the cap are worn out( looks like the rotor button was touching a few on one side of the cap) and the other side look hardly touched. This is still a new build but hasn’t been on the road properly yet apart from a few miles last week, and it drove terribly. I guess my question is stick with this Mallory or rebuild a crab with points? There’s no vacuum advance to the Mallory, and I’d have to drill and tap the thickstun twin carb manifold to get a vacuum port, also how does the Mallory work without vacuum port? Is it just a race distributor or will it work ok on the street? Thanks Dan

[Tim Ayers]

Can you confirm if the rotor hitting the contacts? May need to unplug and unbolt it and take it off to check.

[Ronnieroadster]

While the rotor touching is a problem if that's what you determine as Tim above wrote once you remove it from the engine. But I doubt that's the reason your engine will not run. The Mallory will fail if the ignition feed is left on for an extended period of time with out starting the engine. Check to see if you get any spark.
Remove the coil wire from the cap and then spin the engine over? Check to see if a there is any spark jumping to ground when you do this.

Mallory's will work fine on the street but the electronic versions such as yours are suspect to failure. The version with points and condenser are far more reliable and any parts needed cost a lot less compared to the electronic versions. The advance system is in the bowl its done by centrifugal weights moving by the RPM to give advance its definitely not a race version.
Ronnieroadster

[Ggmac]

What volt are you running? Neg earth? Assaid the mallory point version is great , the unilite version is hit or miss , though the module price has come down .
You are better off using a non vac unit cause the original uses vac with a brake . For performance I’ve had easier set up using straight mechanical advance eas with more than one carb , the others can better advise on that last statement

[Brian]

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The thickstun should have a vacuum port on top, midway between the two risers

[danliveshere]

Guys a bit of back story. The car and engine had been sitting many years and the old stale fuel was my number 1 suspect. I drained all the old fuel and cleaned the 3 fuel filters but was still running rough. It made it a few miles getting my roadworthy and registration process and drove it back on the hoist. Cleaned fuel filters again( wasn’t necessary). Changed engine oil and did various other items on the car. A week later it’s trying to fire but won’t run. Fuel pressure at 3 psi, but can’t adjust it lower till it starts running properly.
I just found a new old Mallory crab unit identical to what’s in it now so will swap them over and let you know what happens. I don’t think I’ve left the ignition on for any extended period, but I guess the red box could have got fried. Will swap distributors and report.

[Tim Ayers]

I’m not 100% sure, but I thought those Unilite Mallory’s used their own cap, similar looking to a crab, but different with male ends.

[danliveshere]

Guys is it required to use a Mallory power cell MAL-611M with this unilte distributor? It was on the engine when I bought it. I also haven’t used a resistor with the coil. So maybe I fried the distributor?
So I’m going to replace the Mallory distributor rotor and cap and the coil. This old Mallory coil( nos in box says to use a Mallory 700 resistor, but I can’t find one as yet. Let’s see what the parts place suggests!

[tubman]

The only posts I 've ever seen on Mallory Unilites have been about problems, and I remember seeing a lot of them. A ford crab set up properly has a reputation as one of the best ignitions around. Just sayin'.

IIRC, it was originally designed by Mallory.

[deuce_roadster]

I had a Mallory point style distributor on my roadster for 7k miles with no problems. I would take the distributor off the engine, clean the inside of the cap, grind 1/16th of an inch off the rotor tip, put it together and spin it in your hand. If the rotor still drags on a post, try a different cap and or take another 1/16th off the tip until it spins freely. I am surprised that the rotor contact didn't turn sideways, that screw on top holds it in position. In my opinion the rotor is a poor-quality design with so much of that part sticking out. Do you have the thin gasket between the cap and body of the distributor? (no vacuum, mechanical advance only on point style I had)

[glennpm]

I've run a Mallory Unilite on my SBC for decades with zero problems. It was a replacement for a dual point Mallory that also ran great. The images below are part pdf the installation pdf attached.

[Ronnieroadster]

Originally Posted by danliveshere

Guys is it required to use a Mallory power cell MAL-611M with this unilte distributor? It was on the engine when I bought it. I also haven’t used a resistor with the coil. So maybe I fried the distributor?
So I’m going to replace the Mallory distributor rotor and cap and the coil. This old Mallory coil( nos in box says to use a Mallory 700 resistor, but I can’t find one as yet. Let’s see what the parts place suggests!

That's a good decision to replace that distributer. Hopefully who ever your parts place is helps you by using a distributer with one that has points and condenser. As I wrote above you will be many dollar's saved initially and well into the future once you have the engine running again.
Ronnieroadster

[Cptkoberg]

I replaced my Mallory unit, after dealing with similar issues, with a Stromberg E-fire SBC-21A-12 from Summit. Been happy ever since.