I am trying to run a mechanical advance mallory uni lite distributer since my tri carb set up won't give the right vacum for a vac-advance (vac drops off when outer carbs open up progressive). So now I need to adjust the advance because the total advance is a bit high. I went to the mallory website and found instructions once you get the distributer apart, but I am looking at this thing and am not sure how you to even get in there. Do you pull the gear off the bottom? There is a roll pin in the gear and I would jump in and pull it but I have screwed up roll pins before and not been able to get the right size back in . . . feeling a little timid and its a pretty spendy piece. Is there a manual? After I get in it seems like I need to just buy a kit which has different spring sets and follow the instructions. . . anything else I might need to know?
if you have the correct size pin punch you won't***** anything up,also make sure to install a new pin when you reassemble,you'll be ok.if you're really nervous about it send it to me,i love distributors,or any other job where i don't have to lay around on the cold garage floor-george
I know what you mean yorgatron- bench work is a welcome break. So you are saying that pulling the gear is in fact the thing that makes it all come apart?
tell you what,i'll run out to the garage,i got a mallory i'm not gonna use,i'll take it apart and get back to you in an hour.
ok i'm back.i removed the roll pin,then i had to pull the breaker plate,then the whole thing came apart.if yours is electronic (no points) the breaker plate is the part that holds the pickup.make sure you measure the gap between the reluctor and the pickup so you can put it back together right.these things are made to come apart for fine tuning,there shouldn't be any surprises in there.BTW if the shaft doesn't want to come out there may be a burr on it where the roll pin/cam gear was,you might have to give it a pass with a file-george
it's been a while since I did mine and it may be different, a dual point converted to unilight, but I did not have to pull the gear or shaft. just the breaker plate. Paul
What kind of engine are you running? Is it for street use? If so, then I'd say you want to use a vacuum advance distributor. Keep in mind there are two advance mechanisms at work in a vacuum distributor used on a GM engine. Centrifugal (some call it mechanical) and vacuum. Centrifugal controls ignition timing due to the speed of the engine. Vacuum controls ignition timing due to engine load - and maybe a better way to understand it would be to call it "vacuum retard." GM engines should have the vacuum advance source plumbed to full time vacuum - IE: a fitting below the carburetor*****erflies. If not, in most cases you'll have overheating on hot days in traffic. GM engines require quite a bit of advance at idle and full time vacuum supplies this. When the engine comes under load, the vacuum level drops, the timing retards and the proper under load advance rate is supplied by the centrifugal advance mechanism. Simply put, vacuum and centrifugal advance work together to supply the proper advance curve according to engine rpm and load. And bluntly put, if you're running a centrifugal advance only on the street you're fooling yourself. All that aside, I run a vacuum advance Uni-Lite in my 462" Buick. The distributor circa 1994 or so and it probably has the same centrifugal advance adjustment setup yours has. Looking inside you should see a small tab protruding out of a rectangular hole near the outer edge. There are timing marks scribed into the plate on the outer edge of the rectangular hole. Using needle nose pliers - gently - bend the tab to limit or increase the amount of cantrifugal advance. Each mark is worth 4 degrees so pay attention. A right hand rotation distributor - which I'm taking to be CW rotation - requires bending the tab to the left for more advance and to the right for less. A left hand rotation distributor - CCW rotation - is the opposite. That controls the total amount of centrifugal advance. The rate the centrifugal advance comes in at is controlled by springs and weights. If that's not clear, let me know and I can scan in the instruction page.
OK it's been a while since I've had my mallory unilite apart and it's about 5000 miles away right now so I can't look, BUT you should NOT have to remove the gear to adjust the advance. There is a plastic "key" that you use to adjust the mechanical advance. If I recall correctly, you pull the breaker plate, loosen something in the adavance mechanism (told ya it was fuzzy), insert the key at your desired advance (the key is stepped), tighten up the advance mechanism, & reinstall the breaker plate.
Wow - lots of advice! First- on c-9's question of whether I should be running a mech. advance dist. at all. The motor is a ford 200 I-6 with an offenhauser progressive tri-carb manifold that uses the original intake log as a plenum. In the instructions, Offenhauser suggests running a mech. advance for this set up so I went out and bought the unilite. What about this idea of the vacum dropping off at the primary center carb when the secondary outer carbs open up? Does that make sense? By the way C9 I just read your book - i liked it a lot. The personal history of rodding point of view is what gets lost in all the history books - but you deliver it in your book. -And back to the dizzy. . . I am at work now but when I was looking at the thing with the cap off it seemed like the pointer thingy (rotor) was permanently pressed to the top of the shaft. There was no visible (to me, anyway) mechanical attachment. That is what lead me to thinking the gear had to come off the bottom. I'll look closer tonight. Mallory sells two different kits for adjusting the curve and they say you have to open it up to see which type you need. So I'm just trying to do step #1.
[ QUOTE ] it seemed like the pointer thingy (rotor) was permanently pressed to the top of the shaft [/ QUOTE ] I might be missing something here - how would you change the rotor if it was permanently attached? They are a very snug fit, but all of mine pull right off - you are talking about the rotor itself, right? Pop it off & you should be able to unscrew the module & set it aside (can't pull it out w/o destroying the plug). Then you should be able to unscrew the plate the module bolts to - if I recall, they are screws that go horizontally into the housing from the inside out - tough to get a screwdriver on, but not impossible. Then you should have access to the advance mechanism. Then again, it's been a while since I've had mine open!
First up, I'm surprised Mallory makes a Uni-Lite for the 200 I6. Sounds like you're taking the dropping vacuum read off a fitting below the throttle blades. In other words, full-time vacuum. That's normal. If you're taking vacuum from a carb fitting above the throttle blades you'll see an increase in vacuum levels as a function of engine RPM. Which is the way some Fords do it, but the best information I can come up with - considering my limited reference stuff on the I6 - is the stock I6 has both centrifugal and vacuum advance and they appear to work very much the same as the GM engines. Figures I found for a stock engine are: 6 degrees BTDC. (Initial.) 28 degrees all in @ 2300 RPM on centrifugal. Making a total of 34 degrees which is about right for most engines. Vacuum advance is all in at 25" of vacuum, but you won't see those levels unless your rings and valves are very well sealed and you are decelerating at a higher than normal RPM. (Like in backing off the throttle with the RPMs up there.) Full vacuum advance adds 21 degrees BTDC. (All figures in crankshaft degrees.) Vacuum advance starts at 5" of vacuum. As a small matter of interest, vacuum levels when cruising a flat highway run 18.5 - 19.0" on my fairly well sealed 462" Buick in the 32 roadster, but, this is a light (2400#) car with big engine and it doesn't take much throttle to cruise at 65 mph. Depending on the weight of your car (3200#?) your highway cruising vacuum levels at say 65 mph may run from 14 - 16" or so. The smaller engine will be working harder to maintain the same speed and that's why the lower vacuum readings. Normal intake manifold vacuum levels run 17-19" at idle with a stock cam. The same figures hold true for a multi-carb setup that idles well. Add a hot cam and idle vacuum levels drop. For V8's it goes to about 11-13" of vacuum with a cam of 280 degrees advertised duration. Spin the hot cammed motor up to 1100-1200 rpm and vacuum levels will be about the same as a stock engine in an equal well-sealed condition. Looking from here and taking into account my preferences, I'd run this engine with the same curve as stock on the centrifugal side and try to bring the vacuum curve into similar compliance. All in on the centrifugal by 2300 is just about what most drag racing curves call for so it should work for you. You might give some thought to having a tune-up shop put your distributor on a distributor machine and checking operation as well as the advance curves. Offenhauser's advice to run a mechanical only is good advice for a race track engine, but for street, a well functioning and properly curved vac advance distributor with the proper curves on both centrifugal and vacuum is the hot ticket in my book. Speaking of which - books that is - I'm glad you enjoyed the book. I'm guessing you're talking about the CHR book and not the Pinky book. Regardless, thanks for the kind words....
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