im planning on running 2x2 intake on my stock 8ba flathead. im using 2 8ba 94 carbs. any suggestions on the type of distributor i should use? im told the stock one will not work well for dual carbs. thanks
i haven't heard that. i also couldn't imagine why it would be so. i too am running an offy 2x2 dual and two holley 94's. i have never heard that. two carbs will give you more fuel, and your stock ignition system should be able to ignite the mixture. you could get a coil that puts out more voltage, but your stock distributor should work fine.
the problem you will have with a stock 8ba distributor is that two carbs under a load (mashin the pedal) will not create enough vaccum to advance the distributor far enough, so you need a mechanical advance dist. you can get an old mallory or a new one but the new ones are billet if that doesnt bother you then get a new one summit has new dual point ones for 200$ or electronic ones. if you need one to look period correct get ahold of matt ( fox valley hot rods ) here on the hamb he rebuilds those old mallory's (and strombergs too) and probobly has one, he's doing one for me right now. and he really knows his shit, helped me a ton. hope this helps
The answer is yes it can be done but it is not the best option. Vacuum on these flatheads is the issue here, the vacuum needs to be hooked up to the venturies on the 94's in order to get a proper vac signal. And running two carbs doesnt double the vacuum it divides it and doesnt provide enough vacuum to advance the timing during higher rpms. 286merc has written a tech article on this in the hambtech files. Lots of info here regarding this subject. Do a search. My 8BA is running a stock dizzy but i think by the sounds of it, I was lucky its running well. Bruce Lancaster always suggests to check it with the US Naval flotation test before using.
Thanks for the kind words Ken. It's not that you "can't" run a stock distributor with 2 carbs, but to do it right you need to modify the distributor. I have a customer right now who I rebuilt 2 Stromberg 48's for him for his 8BA. Stock jetting. He came back to me a month later wanting it to be "jetted down" because it was running too rich. I was puzzled. I've run 2 48's lots of times without a problem. I asked what ignition he was using.....there was the problem. He's useing a stock distributor. Jetting was good, just not getting the advance these old flatheads need because he switched from a stock 1x2 intake to a 2x2 intake. When installing 2,3 or 4 carbs on a flathead, it is necessary to install a large vacuum diaphragm (Holley part #35D-132A) Actuating rod must be rotated 1/2 turn. Change the advance springs to light or remove one spring and adjust eccentric posts to achieve vacuum and advance setting for maximum performance. The real hard part is finding one of those old large diaphragms. I have been looking for one for a year now with no luck... Matt
Mallory made a three port vacuum valve years ago to ensure that even their distributor received the proper amount of vacuum on flathead engines. I'm sure it's been out of production for decades, though. I think that the part number was 24980. I've had a few N.O.S. ones over the years that I've sold, and still see them at swap meets occasionally.
The stock dizzy works well on a stock engine. If the motor has a cam and carbs, the stock dizzy works very poorly. I asked all the old flathead guys and settled on a Mopar 318 dizzy modified to fit the 8BA front cover. With a custom curve, the motor has never missed a beat, always starts, stays cool, and goes like stink. Email me for more info if interested.
Woops, I forgot to say, the whole thing with machining and all new electronics and custom curve, it cost about half what most of the new units cost.
http://www.fordflathead.com/index.html These guys can modify a MoPar early 70's non-Lean Burn dizzy to fit an 8BA flatty. They have both mechanical and vacuum advance that can be tailored. It's a really clean install, looks a lot like a stock one, but uses the ultra-reliable (and cheap) old MoPar toothed-wheel reluctor, and either the typical MoPar standalone electronic ignition module or an MSD. I believe they can curve it for you too.
I have the item that you need for your distributor to compensate for multiple carburetion. The picture is below. This is called the "Vac-U-Trim" It threads into the vaccum advance unit on the distributor and allows you to adjust the tension of the diaphram to compensate for the vaccum change with the use of mulitlpe carbs. Here is the description out of the 1965 Offenahuser catalog: "The precision micrometer-like adjustment in the Vac-U-Trim offsets the lack of vacuum control resulting from mulitple carburetion. Ends ignition adjustment troubles on late or custom engines. Enables you to make micrometer-like adjustment on the ignition of your car. Provides maximum engine performance, eliminates engine ping without loss of horsepower. Enables adjustment of ignition to atmospheric conditions and changes in altitude. Eliminates engine lag caused by sudden acceleration. Reduces stalling due to unbalanced distributor action. Improves gasoline mileage. Maximum engine performance through precision ignition control."
You'll surely get different opinions, but I've never had any problems with the Mallory electronic ignition units on both 59ab and 8ba motors. If you set them up properly they should work just fine and you never have to worry about vacuum ever again. Good info here: www.centuryperformance.com And this is a good article on setting up dual carbs: http://www.streetrodderweb.com/tech/0510sr_holley_94_vintage_carburetor/
The Problem with the Ford Dizzy is that it uses venturi vacum and Not Manifold Vacum (will Work Backwards with Manifold vacum!!!). The dizzy can be adjusted for the two/three carb setup. But its marginal from the start so why not get an aftermarket mechanical advance type. If you dont belive me read what Barney Navarro wrote in 1954, still true http://www.btc-bci.com/~billben/navarro.htm
Offenhauser and Eelco sold alot of the Vac-U-Trims. Offenhauser used to include it with multiple carb manifolds. It is very simple and easy to use. These instructions are for Ford distributors. You remove the spring from inside the vaccum advance unit. Then screw the Vac-U-Trim in where the vaccum line goes in the vaccum advance unit. The Vac-U-Trim has a fitting where the vaccum line connects to it. The rod on the Vac-U-Trim end places pressure against the diaphram in the vaccum advance unit. By screwing in the adjustment you increase the amount of vaccum required to advance the distributor. By screwing out the adjustment you decrease the amount of vaccum required to advance the distributor. Dan Marvin, Owner Exeter Auto Supply
The Jalopy Journal
