I have several Mallory flat top distributors for different V-8's, and all are mechanical (no vacuum) advance. Does anyone have: pics of one with vac adv, including the inside; converted one, by adding a vacuum advance; or any other tips??? I have an SBC overheating problem (210-220°) ONLY at long idle periods, and suspect my mechanical advancd Mallory. Radiator, fan and pump are working ok. Thermostat is Robert Shaw 160°. I changed out advance springs per Mallory kit, but that was '87, so the memory cells have died. BUT, once I'm moving 15-20 mph, temp comes down. With no hood, good radiator and pump,, was I wrong in discounting airflow? Or am I barking up the wrong tree about the advance? Maybe GMCBubba is still on here?
I had that problem on my SBC (350 Swirl Port) in my '55 F100. Adequate fan, etc. 160* thermostat. Changed thermostat to 190*. Problem vanished, now stays at 180-185. Lower temp thermostat doesn't keep water in the 'heater' (block) long enough for the radiator to do its job.
I agree with Mike. Too low of thermostat temperature, and the water is just moving too much and not having enough time to transfer the heat. Try a 180 or a 190 and see what happens. It's not the advance timing as there should not be much advance in, if any at all, at idle. Sent from my iPad using The H.A.M.B. mobile app
That depends where the advance can is attached to vacuum source. There will be advance at idle with the distrubutor connected to manifold vacuum instead of ported vacuum. Like mentioned earlier, rule out air flow and thermostats but don't overlook timing options. Cars with mech advance or dual points were not designed to idle for long periods, more so to haul ass.
Big Duce, I agree with you but if you notice in his original post, he said he had NO vacuum advance, just mechanical. Just my two cents..... Sent from my iPad using The H.A.M.B. mobile app
Yes, i noted that. I too wished there were a flat top old school dist that had vac advance. Might just try a reg points dist with advance to see if that helps the heat issue at idle before custom building a dist. Sent from my SM-G900P using The H.A.M.B. mobile app
Good idea. I have a stock SBC with vac adv. Anyone have any proof of the existence of the elusive vac adv Mallory?
Here's info from a post I made on Nov. 12, 2016- "The Y means it is centrifugal advance only, C tells us it uses #24875-B points and a #24878 breaker plate and the M suggests it is for use with the Magspark, unless someone modified it as mentioned above. Your other one is Z, for both mechanical and vacuum advance and the C as above." While a ZC prefix on a Mallory would designate it as having both mechanical and vacuum advance I don't have any early p/n's so I have no idea which engines they may have been available for.
Here's a scan of an old Mallory master parts list showing the advance system on a ZC. It is not like the typical vacuum canister you are familiar with.
I've had a few of these over the years. IIRC they have all been for Olds Rockets. I will try to get some pics. It might take a few days. If I havent replied by Friday or someone else hasnt posted a pick, send me a reminder PM.
The vacuum setup on flat tops is a BRAKE that slows advance curve at high throttle openings. Same system as '32-48 Fords, whose basic distributor design was by Mallory...both the point setup and the vac brake. A difference is that the flat tops oddly lack an adjustment. Flathead ones were meant to be cranked down on engines with pinging problem, usually a symptom of crap low octane gas. Now, the worst gas available is super duper octane by 1930's standards and most flatheads are happy with adjustment almost all the way out...you can't totally back it off because you need a slight drag to stabilize the floating brake disc, something to think about here.
Nope! I have a ZC too! Question is does a pertronix for a YC fit a ZC? I don't see any ZC listed on pertornix's listings for mallory? I am also posting all the pertinent Mallory Information I collected from the hamb while researching! At least I confirmed this is for a 392 Hemi - so shaft length may be right making it easy.
They came both ways and a vacuum advance will not make your engine run cooler. Running hot at idle can be from a multitude of problems. Hoodless and no shroud could be the problem. Also bad pulley ratio can be a problem or wrong stat. I know that is not what you want to hear but it is not likely that a vacuum advance is going to cure your problem.
Looking at the first post, it should be obvious that the problem is air flow. Shrouds generally solve this kind of problem.
I called pertronix and you can get a unit for the ZC Mallory even though it isnt listed under the Mallory distributors in their catalog. Pretty cool to know. Especially for the future knowledge of all the experts on the board here.
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