I’m interested. So, would these get along with manifold vacuum? Some of my engines like it and some don’t. The 8BA definitely doesn’t like it with the stock distributor.
I've used several of Bubbas converted Chevy distributors with mechanical advance in my flat heads with no problems.
GMC Bubba's is the only way to go. Mechanical advance and recurved to work with my 8ba and it runs so nice!!! You won't be disappointed.
Most people will tell you that a vacuum advance properly set up will provide a better running engine and better fuel economy than straight mechanical only. It should be noted that just about every distributor offered by the major carmakers before the advent of modern electronics operated with vacuum over mechanical. Those that didn't (i.e. Fords Loadamatic that was vacuum only) aren't generally well thought of. Mechanical only is great for racing, but fuel economy (and sometimes driveability) will suffer. Both of the gentlemen listed are excellent choices and are quite busy. I would inquire as to the potential delivery schedule and go with that.
I have a Bubba's mechanical only unit on my F-1 pu w/mostly stock 8ba. Runs fantastic and gets 18-20 mpg on the highway. Highly recommend Bubba's...
An other option is to re-work an early 1980s Chrysler 318 electronic dissy. Has both vacuum and mechanical advance and looks much like the original 8ba dissy. e mail me at [email protected] if you want more info
I didn't know you could buy one so a couple years ago I made one and it's been trouble free. Probably a two hour job.
The stock 8BA distributor uses the "Loadamatic" advance system mentioned earlier, and it was designed to work only with 1 stock carb. And that carb was equipped with psasages to pick up what was termed as "venturi vacuum", which was picked up just below the carb venturi, but above throttle blades. This was supposed to sense engine speed by way of airflow created vacuum under the venturis, plus sense load due to degree that throttle blades were open to control engine output. It was far better in theory than in effectiveness. Used in at least the years 49-56, replacing with a mechanical advace system, or better yet mechanical augmented by a vacuum system for additional advance under light load and throttle makes a big improvement in engine responsiveness and pep.
It aint for everybody but I run a MSD distributer in my blown 8BA that was pure plug and play. I do not run the vacuum advance, I did add a black cap so it wasn't quite as horrible to look at.
Only complaint I have about the Chevy dizzie in my '39 is the window cap. Just doesn't look right on an old flathead but you got to take the good with the bad.
Bring back an old thread here but did coilover respond to the questions about his converting a SBC dist. to 8BA?
Actually a properly built mech only distributer will get you good mileage too. Of course a lot depends on how the engine is built and who is tuning it I suppose. Not saying anything against Vac advance just being the voice of dissent here. OK back to your regularly scheduled programming. A hypothetical question here. Maybe a wondering of sorts. I wonder if you couldn't run a load-o-matic off of ported vacuum like a lot of later 4 bbls use. Off topic as we are in search of a GM to Ford adapted distributer but now you have my mind racing.
The loadamatic only runs correctly on the Venturi vacuum. And also although I’ve been able to achieve it, on only one carb. Doubling the Venturi vacuum from two carbs cuts down on vacuum.
Gosh, that Chevy on an 8BA looks ugly and out of place. There must be a better way. Here's a Uni-Lite Mallory with mechanical advance.
I am extremely fond of the old "flattop" Mallory's. I am running them in five engines, two 8BA's, two early hemis, and an Olds Rocket. Over the last few years, I have accumulated enough spare parts to last me a couple of lifetimes. To add to the confusion, the "flattop" on one of the 8BA's, is a converted SBC unit.
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