i just read a thread about how vacum advance works and now i'm cofused. my 351c has a dual poit distributor with no vacum advance so do i need to change it?
Do you need to? No. Should you? Probably.
If your car is primarily a street car, I would indeed recommend installing a distributor with a vacuum advance. It will go a long way toward improving cruising performance and your gas mileage as well.
Since you're still running points, that's another reason to replace your distributor. Unless yours is a concourse car, install an electronic ignition distributor. This will also improve performance and gas mileage. You can buy kits which convert a points distributor to an electronic ignition. But since you have no vacuum advance, you should probably get another distributor.
If you don't mind an aftermarket distributor, I highly recommend the Mallory Unilite. There are many good performance distributors on the market. But I personally ran a Unilite in a 351W which was my daily driver for many years. That thing was indestructable and quite literally, "set it and forget it". So, I feel comfortable recommending it.
If you prefer the stock look, you can look for a remanufactured, period correct 351C distributor and install an electronic conversion kit.
Others might disagree about giving up points. There's certainly nothing wrong with running points. But the fact is no matter how perfectly you set them, the instant you start your engine, the points start going downhill. I think you'll be amazed at how much better your Cleveland runs with a new electronic distributor with a vacuum advance.
One more thing: I didn't see it mentioned in the article, but some people get confused as to where to connect the vacuum advance. It does NOT connect to manifold vacuum. Doing so will cause the vacuum advance to work in reverse. It should connect to a "timed vacuum" port where the vacuum increases with engine RPM. This is typically located on the carburetor.
It's easy to find the right port if you have a vacuum gauge. Those things are pretty handy anyway and they're not expensive. The same goes for a good timing light. I also like to install a timing tape on the harmonic balancer. Those things make setting the timing a lot easier. You can simply peel it off when you're done, or leave it on if you expect further adjustments. If you want to leave the timing tape on, it helps to put a dab of clear nail polish on the seam to keep it from peeling off on its own.
I'd like to see a pic of that distributor.
Post a picture of it if you can so Don can give you a heads up on what you have.
thanks and i will post a pic later. this car is not done yet but will just be a sunny day driver so i'm not worried about gas millage, just want it to run good.
(05-11-2011, 10:07 PM)bluestang Wrote: [ -> ]thanks and i will post a pic later. this car is not done yet but will just be a sunny day driver so i'm not worried about gas millage, just want it to run good.
For street cruising, I think your car would run better if it had a vacuum advance. I suspect your dual-point distributor is an aftermarket unit. Is it something like an "Accel"? Those are nice distributors. Or, is it some kind of Ford high-performance unit? I suspect each time you set up those points, an electronic ignition will sound better and better.
BTW, bluestang, what kind of car is it? (I assume it's blue.) :-)
That setup is very rare . If that setup came with your car it could a HO cleaveland or CJ 351c , 4bolt main with a 4 speed . What you need to know is how to set the points . I beleave you need to ajust the first point at just before the number 1 piston hits tdc . Turn the crankshaft just past tdc to set the other side on the points . It is a little harder to do . I think you will need to set them at 19/1000s or the thickness of a match book cover . It should take 2 of you . The motor wants to turn on you as you are trying set each point . It is a pain in the seat . I hope this will help you out . C . L .
I set both sets the same way you set single points, just get it on the high lobe and set it, then turn to the next set. Doesn't matter where the crank is positioned.
a dwell meter is much more accurate and compensates for clearances in the distributor. It has been at least 20 years since I've set any points.
I use a dwell meter to set the points gap. I find it more accurate. Whenever you try to tighten the screws they always end up closing a bit. Easier to tell if you get it right with the dwell meter. When I first got my car it was a bit of a pig when trying to move off. Found that the vacuum advance wasn't connected. After I connected it found a huge improvement.