The Stovebolt Site Forums The Shop Area Engine Shop Stromber 97s and no vacuum advance

My detail planning is limited to one step max including the current step. So, after installing dual 97s on an Edmunds intake I discovered I have no place to connect the vacuum advance. The 97s don't offer anywhere to take vacuum. Nothing on the manifold either. I'm thinking I need to get another distributer that offers full mechanical. Mallory has one - part 4518001. Does that sound like the way to go?

What are you working on/with? Engine and distributor information would help.

You have dual carbs, I'm assuming a moderate to aggressive cam, you'll want to start timing at 14-18 base and have a total of 36-38 mechanical degrees, maybe more depending on compression. You can usually use another 10-12 degrees of vacuum advance on top of that, as long as it too is dialed in correctly.

I've been known to drill and tap 1/8" pipe thread holes in manifolds to get vacuum. You may have to do the same.

Devin

There are vacuum plates available for the 97s, although they are somewhat hard to find. You could drill and tap the manifold, or you could get carb spacers and drill and tap them. I will have the same problem on my 1940 gmc with a 302 6 cylinder and 5 97s. I will most likely machine my own spacers out of billet aluminum

Thanks guys. I'm working on a '61 235 which I think is mostly stock. The engine was rebuilt when I got it and I don't know about the innards. It must be overbored a bit and probably a bit off the head to clean it up but from the sound I would say the cam is stock or close to stock. The distributer is a nice stock NOS one I got last year.

Since I have 2 carbs would the vacuum be 1/2 what I had before if I pulled off a vacuum plate?

The vacuum you need for the distributor, is not manifold vacuum. It's what I believe is called "ported" (I am probably wrong). It comes from a port in the carb, as it advances the timing when the throttle opens, which drops manifold vacuum. If you've got the 97's on there, I suspect the best thing would be to use the full mechanical advance, perhaps dual point mallory. I don't know how the economy and drivability would be, as its a "race" set up.

I'll bet that Edmunds manifold is a real looker!!

Thanks Mr Lang. I read an article last night saying what I need is the vacuum above the throttle plates. That would rule out the adapters bigbadswingdaddy. I did find them but the description just said they provided vacuum. It didn't say how that vacuum was to be used. I think I'll give the vendor a call Monday and see what they say.
I played with tuning them yesterday and got them to play better with each other but still have the front one pulling more air than the rear. They sure did wake up that engine.