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Vacuum advance, springs, etc.


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6:23 PM
Apr 27, 2021
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I have a couple of projects I work on for fun. I'm not a pro and learn as I go.
I've got a 440 I've been reviving that was stashed in a garage for 27 years and have been having decent success replaced the tank and fuel lines, sorting out the cooling system and I've put disk brakes all around. The 440 is original to the car and I was careful starting it since it had been down for so long. It runs and I'm working out a few other loose ends now. The previous owner has passed away and I don't have a solid source of information anymore, but according to him the car had been bored out 60 over and has some sort of purple cam in it.

I've recently learned that the current carb is a 600cfm Holley, and a local carb shop set me up with a rebuilt 750cfm. Before I took it home, he demonstrated it on an engine on a stand that he uses for that. Now as look at swapping it in, I see that it doesn't have a connection for the distributor's vacuum advance line. There's a port there, but not the tube I would expect. The hole is not threaded.

I asked the carb shop about that, and they suggested I use different springs in the distributor and just forego the vacuum, especially since this car has an aftermarket cam. Can anyone recommend where to start with this? I haven't done anything with springs on a distributor before.
I already have a Davis Unified distributor waiting to go in, but I'm expecting any info that would apply to springs for a stock distributor might hold true for that.

Any suggestions on where to start?

by looking at the carb with the choke tower removed i think it may be a hodge-podge of parts. looks like it may have been a 4160 style that somebody wanted to hot rod. anyhow, the recess above the mixture screw on the right side of the carb (vacuum secondary pod side) can be drilled and a tube added. to make sure that this is possible you may need to disassemble the primary metering block and make sure all the necessary passages are there. better yet take the carb back and fix your 600 or buy an unaltered carb. if your intent is to drive the car a lot than a vacuum advance is advisable.
Few things; your vacuum secondary 4150 750 looks good. Even better that it's been tuned/tested. They are completely correct, with a cam etc, a recurved distributor advance with no vacuum advance is the way to go. If you already have a new dist, put it in and see what the advance is like.
When you put the carb on, you may find the secondary pod linkage hits the intake.
After all that, if you still want to struggle and fight to make the vacuum advance work with the non stock cam, the port should be on the lower front pass side under the fuel bowl.(like your original carb.
You're asking a few different questions...no problem. If you just want to drive the car, then leave the 600cfm Holley on it since it's not "that" small. On the 600cfm Holley, that tube has "venturi vacuum", which is what Chrysler used originally (can of worms opened? check).

If you're trying to go faster, a 750 vacuum secondary Holley like you have is a good choice (probably a 3310-3 carb or similar I guess?). I've run a 750 Holley Vac Secondary on a stock 440 intake. There is a clearance issue with the 750 Holley on a stock manifold (2 locations I think....the bottom of the vacuum secondary; where I clearanced the side of the intake 1/8" PLUS some return stop (?) on the other side of the carburetor; where I clearanced the bottom of the carb itself). Otherwise, you can put a 1/2" or 1" spacer under the carburetor and I think everything clears if I recall correctly.

As for your vacuum advance, with the 750 Holley, you have 3 choices.
A. Drill/tap the metering body and add a nipple (I've never done this, but it may be possible...I'm not sure, but sounds reasonable)
B. Use the nipple on the base plate of the carburetor as mentioned....however, that is "ported" or "direct" vacuum (people debate A LOT about using venturi or ported vacuum for vacuum advance)
C. Don't use the vacuum advance - this is how my motor is set up simply because my engine runs better without vacuum advance.