The Stovebolt Site Forums The Shop Area Engine Shop mallory dual life distributor in a 235

any one got experience good or bad? I am swapping out the vacuum distributor to the mallory now

What kind of racing are you doing? It's worthless on the street. Dual points are double trouble, especially if you don't have a Sun didtributor tester to do the setup, and the lack of a vacuum advance is going to cost you a couple of miles per gallon- - - -not exactly a smart move with gas approaching five bucks a gallon.
Jerry

I have a 235 with mcgurk dual and carter w1s. it is a daily driven truck to and from work 22 miles a day. future engine will be a McCullough supercharged 261 with a wico magneto

Just a friendly word of advice. In the future when posting about hot rod stuff use the HiPo Forum to avoid the above unrelated thread hijacking.

Might Consider a s10 v6 HEI dizzy (and coil) modified for our inlines, fires a .060 spark plug gap all day long, parts available locally, proven reliability, no points…..

what's the points gap for the mallory dual point?

It is really iffy setting dual points on a used distributor with a feeler gauge. You can pull the plugs, cap, and rotor and hook up a dwell meter and set one set of points while other set has a matchbook in them. Spin engine with starter and set dwell. Repeat for other set. It has been so long since we have used points I forget each points dwell and the total. We do have this gathering dust for years:

[img]https://i.postimg.cc/XrX0njk5/IMG-4312.jpg[/img]

The only time the cover comes off is to check out whether a magneto needs degaussing.

I know the dwell specification and how to get it there, having set up dozens of race engines with Mallory dual point distributors.

Good luck. I hope you've also got the special tool for setting the centrifugal advance, and the specification for the three possible different advance numbers it is able to set.

Only one of them is correct for a stovebolt engine.

Jerry

Spico Seems like a simple HEI would work as well,be hotter,easier and cheaper to work on.

coilover Hadn't heard that term in 50 years,an old mag fixer had the oilfield guys convinced of some hocus-pocus he done for 2$ to their mags...you'd see him pocket the 2 $ cigarette money Lucky's .25$ LOL

At one time dual points were the rage, and truth be told, there was a benefit to using a dual point set up under certain circumstances. The issue, that time has long since past. Just as a threshold issue, for a street driven car, you really do want vacuum advance. Second, an HEI would be way way better then a dual point Mallory. Hotter spark, way more reliable, parts are available over the counter, well proven ignition with a vacuum advance. Otherwise, unless you are running high rpm, which is where the dual point could make a difference in terms of coil saturation and field, have your stock distributor rebuilt and stick with the stock points. Just a thought.

The only benifit I could see, if a stovebolt was built to produce RPM’s well above 5,000. I had one in my 67 GTO and it was more trouble than it was worth. It was nice eye candy though!

Tripple X on the HEI!

The HEI reluctor and pickup coil can be installed in a small diameter housing like the one used on the 230/250/292 six, with the module on a heat sink mounted out of sight, like maybe under the dash. It only takes a little bit of machining to make the 250 housing fit a stovebolt, and parts like the vacuum advance are much more available and less expensive than the movable housing stovebolt distributor. Running dual points is about as logical as cutting holes in the floorboard for Fred Flintstone brakes!
Jerry

Doesn't Langdon sell this sort of stuff already setup for a stovebolt? Just a bolt-in?

One question about vacuum advance: A 450 GMC dump truck that was in a fleet I took care of had a 270 (or maybe a 302, don't remember) did not have a vacuum advance at all, only mechanical. I always figured it was because it was pretty much a binary operation -- idle or foot to the floor. Even with a 5spd OD and 2 spd axle It was not fast and used a LOT of gas.

At times when the vacuum advance on my pickup has failed I found it overheated the exhaust manifold and burnt the gaskets out. One time was an inconvenient repair in Boulder, Utah. But NAPA had the gaskets and the advance unit. Why didn't the big GMC behave similarly? Apparently it's not always needed. My pickup runs flat out much, but not all, of the time. It uses a lot of gas too. Pickup sits out in the yard and there are 5 motorcycles in the shop. Suppose that has anything to do with gas as $5.59. Ethanol-free is only 10% more. I recommend it for all the motorcycles. They don't always listen. That's why I've done so many carburetors lately. It's the pilot jets, stupid. It's the pilot jets.

Gad! Topic drift all in one post. Sorry, I'll promise to be more on point from now on.

The primary (really the ONLY) purpose for vacuum advance is to nurse a little better gas mileage out of an engine at light throttle cruising speed. An engine that's not lugged down or trying to accelerate can tolerate about 10 degrees more spark advance than one that's pulling hard. Big trucks and good gas mileage are about as compatible as oil and water. There was no need for that extra advance, because it was seldom, if ever going to happen- - - -there is low to no manifold vacuum at full throttle on any engine, especially one that's pulling hard most of the time. The centrifugal advance just has to be set up ro deliver maximum torque at the desired RPM, which requires a close coordination of compression, camshaft profile, and ignition timing. Aircraft piston engines also don't have vacuum advance, and sometimes even the basic spark timing is manually controlled. Ditto for Model T and Model A Ford engines, and 1920's and early 30's vintage Chevy engines.

Doing race engine stuff, or heavy truck stuff on a street engine in a light truck or a weekend cruiser is beyond foolish.
Jerry

man I guess I don't hang out here because of all the 'this set up is better than what you are wanting to do because it's easier than what you are trying to do' guys giving their advice. yeah I get it a hei is easier and better. I get it. I also understand if I want a s 10, I'll go buy one rather than sticking a 75 year old sheetmetal ontop of it and saying I got a classic truck. I get it and I'm not asking you for whats better and what I should do in your opinion with my truck. what I was asking is if anyone had experience with a mallory in a 235. I understand I am fighting the last good fight and technology has advanced and that is why no one does it. but I don't care about what advancements have been made over the last 2 decades for the simple ease.

Since your set on using the dual point distributor, I used to set up a dual point in my 67 GTO by removing the distributor, clamping it on a vice, isolating one set of points with a business card, driving the distributor with a drill and setting the points with a dwell meter. I had no luck setting them with a feeler gauge and at the time I didn’t have the extra cash to have it professionally setup at the speed shop. It seemed to work as the engine ran pretty well after.

I have the experience. And I advised that you should reconsider. I did not tell you to do anything, or insist that you do it my way, I advised that it was not the best or even a good alternative.

HRL noted one of the issues with a dual point, getting both sets of points set up correctly. Dual points require frequent adjustment because they frequently go out of adjustment. That is from my experience with the Mallory. Then your motor runs at less then optimal efficiency. That has also been my experience. You were advised by a number of folks to reconsider the dual point and think more in terms of an HEI.

Ya'll want to argue about technical stuff back and forth, go at it all day long if you like, as long as you keep it polite.

It's just old truck stuff people, no need to get personal or start name calling.

Also, don't go around the profanity filter, the Editors look dimly on that.

watching in the wings...

-Woogeroo

Martin It is still kind of dangerous even in the Hipo forum. LOL

Woog Your right,it's your truck try anything you want to,that Mallory is 3 lobe ???? Can't recall how it looks,probably never even saw one anyway!!

I'm a bit "late to the show", but I'll also be running a dual point distributor. After reading the info here, I'm not looking forward to the experience!

Drop me a PM and I'll give you some pointers on how to set it up. It's eye candy like dual carbs and "Fenton" clone headers, but it can be made almost as good, even if not as reliable, as a single point OEM distributor.
Jerry