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Mallory unilite dist

4K views 31 replies 9 participants last post by  stevo camaro 
#1 ·
Wondering what people's thoughts are on these distributors. It's the mallory unilite with vac advance. I've used one in the 327 for 22 years and haven't had any problems with it.
Running another one just like it in the 427 I just installed. In trying to dial in the 427, ( timing and carb adjustments), I set my initial to 18*. Motor likes it. But after I plug in my vac advance, ( to constant vac), I get a reading of 45*. At 2200 + it runs up to 55. Not sure if these dist. have an adjustment inside or not. And, I am using a dial timing light. LOL
I've been reading on how many guy's hate the dial timing lights. But hell, how would I have ever seen 55* without it. LOL
Anyone well versed on the mallory?
 
#3 ·
Sounds like you need to install a positive stop on your vacuum advance can to keep your total advance within more reasonable limits; 45 sounds high. Search for postings by Dave Ray concerning distributors, vacuum advance and dial-back timing lights.
 
#4 ·
Yeah, I agree. Caps gonna get popped off. I'll peek inside to see what I can see. LOL
 
#6 ·
I have one and Holley still has the instructions for installing one.
https://documents.holley.com/mallory_instructions_unilite_distributor_37_38_45_47.pdf

They are supposed to have 24 degrees mechanical advance. They recommend setting initial at 12 degrees (12 + 24 = 36 total)

The vacuum can should add around 15 degrees. You can add a stop to tailor how much advance it adds; most people recommend 10 degrees

If you raise the initial to 18, you should lower the mechanical to 18 to keep 36 total.

They sell an advance curve kit; I haven't had a chance to try it :

https://www.summitracing.com/parts/maa-29014/
 
#7 ·
I looked inside this unit and there's no mechanical advance at all. No springs. Just the vac. rod. Someone said I shouldn't disconnect the vac advance while timing this type of dist. Time it plugged in. I'll give that a try and see what happens.
 
#10 ·
No, I pulled the rotor and trigger plate too. There's nothing else in there but the module and vac advance rod attached to the plate. Plate moves freely. It was new in the box. I'd say it's about 15 years old now. Looks like this dist. gets all it's advance from vac.
Talking to a guy today, who's a mechanic by trade, say's I need to leave the vac hooked up to get the initial on this type. Really? I've never done that before.
I'm going to look at the one in the 327 tomorrow. There's probably a difference between the 2 somehow.
 
#13 ·
Mechanical advance is under the plate. You have to disassemble the dizzy to get to it. remove gear and pull the shaft. Go to the holly website click Mallory Unilite and download the manual.
 
#14 ·
SteveO I had that same dist. in my 69. Here are the issues I had with mine. Previous owner had put the wires to close to the shaft, it rubbed through and grounded them to the shaft intermittently. Car would occasionally buck and snort and stop cold turkey. Then start up again.That sucks. I took it apart, it was dirty, cleaned it up and bought a new module kit and got the Vac arm put back onto the pin again and then things ran much better :)
 

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#16 ·
Yeah Jim, I had a problem with that trigger plate rubbing thru the red power wire on the RS 20 years ago. Fixed that and haven't had a problem with it since.
Looking at your pics, the plate that moves in the dist. looks pretty flat on the aluminum housing. Looking at the holes drilled in it, all I see is the housing. And there's springs under that? Doesn't look to me like there would be anything under it.
Wish you had a pic with the plate out. LOL
 
#17 ·
Looking at your pics, the plate that moves in the dist. looks pretty flat on the aluminum housing. Looking at the holes drilled in it, all I see is the housing. And there's springs under that? Doesn't look to me like there would be anything under it.
Wish you had a pic with the plate out. LOL
I found a good thread on this.

If someone has removed the advance weights, and some people do, I wouldn't use that distributor. You need centrifugal advance.

https://www.offshoreonly.com/forums/general-q/190088-removing-advance-mallory-unilite.html
 
#22 ·
#21 ·
Thanks for the links. I have the box, I'll get the part no. off it. I know it starts with a 47
 
#23 ·
SteveO I never got down into the bowels of the bowl :) but Im guessing that's where the springs are. I found a few more pics from my disassemble that I did. Not sure what caused that reddish color dust/crap under all the working parts, maybe a lube but it sure cleaned up nicely. It appears there was a 47 black number on the base of that area but it washed off when I cleaned all that crud out of there. You can see it in one of the pics. I have no clue where the springs are weights are at all. It all seems to be a cast alum piece with no access other than the small plug that screws into the side of the base of the bowl. Weird.
 

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#24 ·
Okay, the part # for this dist. is 4748201. I think I'm going to need to change the vac. canister. The mechanical is advancing it 14* at 2300 rpm. The issue I think , maybe, is that after going from 18* initial, it jumps to 45* as soon as I plug in the vac. And after taking the RPM's to 2300 ish, it's stops at 59*
I will say this though, The motor seems happy with it. It fires right up, it idles fine at 1000 RPM, ( not bad given it's cam,) and the car is accelerating well. I seem to have taken the off idle stumble out of the carb. I do need to drive it around more, the registration will happen today. I've been blasting it down the road a half mile and back with no tags trying to dial it in. It runs cool, ( we're still 70 over here). But, I do need to cruise it more that a mile at a time to really tell what's going on I suppose.
I still haven't looked up this dist, number. I'll be doing that now.
Maybe I'm too concerned with nothing. LOL
 
#25 ·
Steve, I looked up that distributor at Summit. Their pic shows a hex shaped vac can.
I think those are adjustable by inserting a hex key wrench though the tube on the can.
From what I've gathered on this post you're getting acceptable mechanical advance but
way too much from the vac can. You may only need to adjust the vacuum.
 
#26 ·
Yes, I believe it does have a hex shaped canister. I'll check that out when I get down there.
 
#27 ·
So I download the information and print out the info on this dist. As I'm reading through it, it says to connect the vacuum advance to a PORTED outlet on the carb.
I've read plenty of discussion on this. The consensus is NEVER go ported vac. Wonder why they're telling people to do this? Are they assuming we're all using them in smogged out motors with 125 H.P.? LOL Things that make you go Hmmmmm. :)
 
#29 ·
Not yet, I'm gonna give it a try tomorrow hopefully. My shop is located 3 miles from my house. If it was here, I'd be in the garage right now. LOL
 
#30 ·
Okay, it is an adjustable vacuum advance. I got as far as finding the right allen and getting it to turn. Then the phone rang. So, hopefully today I can make the adjustment. Not sure which way to turn it or how many degrees it will swing yet. Maybe someone knows? I can figure it out through trial and error.
Put the tags on it monday, so looking at the weather, I have this weekend before we get hit with snow possibly. Dammit! LOL
 
#31 ·
Unilite distributor.......brings me back to Super Shops where that was one of my first performance purchases. Was pretty temperamental so I pulled it out after many attempts and went back to stock. If you can make that work that is an awesome piece of the 80's!!! Would love to have mine back know that I know more and am much more patient.
 
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