Distributors
- Thread starter eeh1
- Start date
corvette8n
Well-known member
If it's a stock setup and your looking to tool around town, the and original vacuum setup is fine, if your running multiple carbs, and a performance cam your looking at a mechanical advanced distributor.
BUBBAS IGNITION
Well-known member
Phil Gillespie
Well-known member
Yes for 8ba the dimple is at 2 degrees btdc.
See Van Pelt site he has all the information for these engines. His list shows 450 to 500. I like around 550 to 600 rpm for idle.
Recommend this site.
Phil NZ
Gene1949
Well-known member
Bubba makes a real good Chev that fits your 8ba. I built one 25 years ago because I put a 56 Buick 4bbl on my 49.. A Chrysler pickup coil/reluctor, a GM HEI brain and a late model E-coil and you are good to go for about 25 years. Never have to worry about spark plugs fouling etc.
IF you have the stock carb and are a purist the old Load0matic works pretty well if properly serviced.
Not a big fan of "all in one" distributors but MSD has a pretty stock looking unit. Not too sure about the reliability of the electronics.
Many of the members here sort of back themselves in a corner by using proprietary electronics (Pertronix or a clone) or mix and match "old school" ignition.
I wanna be able to go to NAPA and fix my outfit off the shelf.
IF you have the stock carb and are a purist the old Load0matic works pretty well if properly serviced.
Not a big fan of "all in one" distributors but MSD has a pretty stock looking unit. Not too sure about the reliability of the electronics.
Many of the members here sort of back themselves in a corner by using proprietary electronics (Pertronix or a clone) or mix and match "old school" ignition.
I wanna be able to go to NAPA and fix my outfit off the shelf.
Gene1949
Well-known member
6 volt ignitions are inherently high maintenance items but that was all we had back in the day. There was also a gas station and backroom mechanic on every other street corner.
Today look at the many threads/problems here on this board. Failure prone (outsourced) ballast resisters and coils and secondary market electronics manufacturers trying to create electronic ignitions for owners of 6 volt cars. Starting issues, reliability, drivability issues, it's all here.
When the point setting gap/dwell changes so does your timing. Flattys are very timing sensitive relating to overheating during the summer.
6 volt ignitions are very hard on components, even the original "good stuff". Due to the high amperage loads to create a spark.
Today look at the many threads/problems here on this board. Failure prone (outsourced) ballast resisters and coils and secondary market electronics manufacturers trying to create electronic ignitions for owners of 6 volt cars. Starting issues, reliability, drivability issues, it's all here.
When the point setting gap/dwell changes so does your timing. Flattys are very timing sensitive relating to overheating during the summer.
6 volt ignitions are very hard on components, even the original "good stuff". Due to the high amperage loads to create a spark.
tubman
Well-known member
I will have to disagree with this. I have a mechanical advance only Mallory on the '51 Merc engine in my '51 Ford club coupe. It starts on the first touch of the key and runs excellently. As a matter of fact, I replaced a vacuum advance converted SBC unit with it when I couldn't get the car to run right with that distributor. I am completely satisfied with the way the car performs with the Mallory and would not consider changing it. Last summer, I made a 280 mile round trip, mainly on the interstate, averaging 70 mph and 19 mpg. This in a car with 3.55 rear end gears and no overdrive.
Also, as I reported in my reply to "adileo" about condensers, After an initial tune up in 1987, this same car performed flawlessly for 30 years and over 20,000 miles until I upgraded the engine in 2017. This was with a completely stock 6 volt system. Just make sure the system is in good shape and quality components are used. A lot of the time, components on cars as old as these are just plain worn out, which can lead to lots of problems (think worn distributor bushings).
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JSeery
Member Emeritus
I have run full mechanical on a lot of vehicles, daily drivers. There is a fuel economy advantage with the vacuum, but not that much in my experience. I tend to like the mechinical only. Had a 73 Country Squire with a 400 automatic that I towed a large boat with, it loved the Mallory mechanical distributer!
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rotorwrench
Well-known member
The vacuum spark control is more of an advantage if the country has a lot of hills or mountains. It needs the retard under load for that. Any car can benefit some with automatic spark control. It helps keep the coolant temps down as well when under load. Centrifugal advance will work OK if there is no other easy method for getting both centrifugal and vacuum controls. Chevy distributors can be set up utilizing the adjustable vacuum can but it takes some trial and error or someone with a distributor machine and experience to dial them in on the bench.
Aircraft engines just have the magnetos set for full advance then use a retarded spark starting aid on one or both mags to get them to start without blowing the starter up. They run well but they aren't know for fuel mileage either.
Aircraft engines just have the magnetos set for full advance then use a retarded spark starting aid on one or both mags to get them to start without blowing the starter up. They run well but they aren't know for fuel mileage either.
tubman
Well-known member
I thought I'd bring this back up because I just got done going through setting up the Mallory dual point in my car after changing points. First of all, the instruction sheet that came with the distributor said that total dwell should be between 31 and 35 degrees which can be obtained by setting the point gaps to .022". I did this, and the engine did not run as well as it did before. Over the next couple of days, I pulled the distributor and reset the points several times to try to get it right. As an aside, the points were extremely difficult to adjust, mainly because the distributor and points set (genuine Mallory, BTW) lack the slots that you insert a screwdriver in to precisely move the points. I could not get it to run right, so I finally broke down and bought an old "Accurate" brand dwell/tach meter off eBay. When it showed up, I put it on the distributor, and lo and behold, the dwell was sitting at a paltry 22 degrees. Obviously, something was wrong. To make a long story short, I changed point gaps a couple of more times, finally setting them at .018", which resulted in a dwell reading of 33 degrees. The car now runs better than it ever did. In the final analysis, setting the points on one of these is a tedious, difficult job, but if you get it right, the results are worth it. Given the variance between the point gap given in the instructions and what actually produced the proper dwell, I would say that a dwell meter is essential to get the points set right.
As someone mentioned above, the vacuum advance starts to come in at idle speed (600 RPM in my case) making the factory timing marks questionable. I finished this procedure by setting the timing using a vacuum gauge. Once it's running, advance the ignition until the vacuum gauge reads the highest, and the retard it just a little, until the vacuum reading starts to drop. That should get you to a reasonable initial advance. I use this technique to set the initial advance on all modified engines I have, because changing cams, compression, and other factors alters the proper settings from factory specs. Once you have the initial advance set properly, you should check for total advance, which may involve making some internal changes to the distributor if it is not correct. However, that's a subject for another day. Some late Mallory distributors come with an advance curve that can be adjusted using a plastic "key" that you insert in the breaker plate to limit the advance. If this is not set right, the distributor may have a total advance built in of 36 degrees, instead of the 22-24 degrees that works best with a flathead. When I dug out the instructions for my distributor, I found the sheet that describes how to use this "key" if anyone needs it.
As someone mentioned above, the vacuum advance starts to come in at idle speed (600 RPM in my case) making the factory timing marks questionable. I finished this procedure by setting the timing using a vacuum gauge. Once it's running, advance the ignition until the vacuum gauge reads the highest, and the retard it just a little, until the vacuum reading starts to drop. That should get you to a reasonable initial advance. I use this technique to set the initial advance on all modified engines I have, because changing cams, compression, and other factors alters the proper settings from factory specs. Once you have the initial advance set properly, you should check for total advance, which may involve making some internal changes to the distributor if it is not correct. However, that's a subject for another day. Some late Mallory distributors come with an advance curve that can be adjusted using a plastic "key" that you insert in the breaker plate to limit the advance. If this is not set right, the distributor may have a total advance built in of 36 degrees, instead of the 22-24 degrees that works best with a flathead. When I dug out the instructions for my distributor, I found the sheet that describes how to use this "key" if anyone needs it.
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51504bat
Well-known member
Consider me as another who disagrees with this. I've been running a Bubba Chevy mechanical advance distributor on my single carb 8ba with EAB heads and a stock Merc cam for several years now with absolutely no issues whatsoever. Starts as soon as I hit the key and gets driven almost daily.