Engine stumbles to a start.

[DuckRyder]

I would shoot for 36-38 with vac disconnected and plugged and in as fast as the engine will accept it without pinging (probably about 2500).

Doesn't the Digital 6 have a start retard (if needed)?

[dustman_stx]

I would shoot for 36-38 with vac disconnected and plugged and in as fast as the engine will accept it without pinging (probably about 2500).

Doesn't the Digital 6 have a start retard (if needed)?

Now that you mention it, I'm thinking it very well could. I know it has a retard setting for running NOS. I'll have to get my book out and see. Thanks for the reminder. So you'd just lose the vac advance all together? This truck is NOT built for fuel mileage, which is the primary benefit of vac advance, right?

[DuckRyder]

So you'd just lose the vacuum advance all together?

No I would plug it to set the initial + centrifugal and then tune it so that it did not ping on tip in or very light load. Most aftermarket distributors are adjustable so you can limit it if needed, also if you carburetor has both ports, you can try switching it back and forth between manifold and ported vacuum. If you have the capability to run it, there really isn't any reason not to.

[dustman_stx]

So you'd just lose the vacuum advance all together?

No I would plug it to set the initial + centrifugal and then tune it so that it did not ping on tip in or very light load. Most aftermarket distributors are adjustable so you can limit it if needed, also if you carburetor has both ports, you can try switching it back and forth between manifold and ported vacuum. If you have the capability to run it, there really isn't any reason not to.

So, if I set the initial at, say 12, and the centrifugal at 36, all in by 3000, what will the vacuum be doing? The way it is now, if I do this and then plug the vacuum advance back in, it's gonna give me in the 60 range.

[DuckRyder]

If you set the timing for 36 at 3000 (and the centrifugal is all in) then the initial will be what it is based on the curve of the distributor. When you plug the vacuum in it might be 60 UNDER NO LOAD, but the vacuum should drop out nearly instantly when the throttle blades are opened, and again, it is usually adjustable with an Allen wrench through the nipple on aftermarket distributors.

It would help if you could give us a link to the instructions for the exact distributor you are using. Most of them come with a pretty long slow curve from the factory.

[dustman_stx]

If you set the timing for 36 at 3000 (and the centrifugal is all in) then the initial will be what it is based on the curve of the distributor. When you plug the vacuum in it might be 60 UNDER NO LOAD, but the vacuum should drop out nearly instantly when the throttle blades are opened, and again, it is usually adjustable with an Allen wrench through the nipple on aftermarket distributors.

It would help if you could give us a link to the instructions for the exact distributor you are using. Most of them come with a pretty long slow curve from the factory.

So, when actually driving and under load, I wouldn't see all of the 60 degrees advance? My 360, with a stock distributor with vac advance, shows 12 initial and goes to 36 or so when revved with no load.

Here is a link to the distributor I have. It's sold as a Summit, but is actually a Mallory Unilite.

http://www.summitracing.com/parts/SUM-850309/

[DuckRyder]

If you set the timing for 36 at 3000 (and the centrifugal is all in) then the initial will be what it is based on the curve of the distributor. When you plug the vacuum in it might be 60 UNDER NO LOAD, but the vacuum should drop out nearly instantly when the throttle blades are opened, and again, it is usually adjustable with an Allen wrench through the nipple on aftermarket distributors.

It would help if you could give us a link to the instructions for the exact distributor you are using. Most of them come with a pretty long slow curve from the factory.

So, when actually driving and under load, I wouldn't see all of the 60 degrees advance? My 360, with a stock distributor with vac advance, shows 12 initial and goes to 36 or so when revved with no load.

Correct, you would only get the full 60 degrees at steady state cruise under no or very light load. Do this, hook a vacuum gauge up to it and watch it (eyes on the road too please) for a few days when you ride around.

Here is a link to the distributor I have. It's sold as a Summit, but is actually a Mallory Unilite.

http://www.summitracing.com/parts/SUM-850309/

Wow, those are not very good instructions, I love summit but they should at least put the curves in there, and to adjust it you have to take the gear off? not very user friendly! That said, I looked up a unilite, and it says "most" of them have 24 degrees of centrifugal. It did not say what RPM it came in by.

Do you have a dial back timing light?

[dustman_stx]

No. My timing light is an old hand-me-down from my grandpa. That sounds about right- 24 degrees- that would put me at 36 with initial at 12. So, getting 60 degrees when cruising is good? Then when I get on it, the vacuum advance goes away, and I'm running only mechanical? How does my vacuum advance only distributor on my other truck work, then? Mine came with different springs, but I haven't messed with any curves or anything yet. Sorry to sound like such a moron about this whol advance thing. Thanks for the help on it.

[DuckRyder]

I think the first thing I would do is try to determine how quick the curve is, you can do that by disconnecting and plugging the vacuum advance and then accelerating the engine (slowly and smoothly) while someone watches the tach (or you watch one if you have one available) and you watch the timing for advance. Record the RPM at which it stops advancing, do it a couple of times. That is your all in RPM. Also accelerate the engine a good deal past the all in RPM to make sure that it really is all in. If it truly is all in by 3000 thats not bad.

36-38 should be about right for a performance engine.

60 total with the vacuum sounds like a bit much to me, which is probably why one of Summits "suggested parts" is an adjustable vacuum advance, but as I said as long as it doesn't cause it to ping, it may be fine. If it does cause it to ping, you could as I said, move it from manifold vacuum to ported vacuum (or vice versa). You also may be able to "adjust it" by putting a plastic hose connector in line with the canister and drilling a VERY SMALL bleed hole in it.

I've never seen a vacuum only distributor, factory Ford distributors have two available centrifugal ranges that can he changed with the orientation of the shaft. If you have one that has no centrifugal advance, it may have been intentionally locked for some reason (usually racing), the mechanism could be frozen or the springs broken (or missing).

Also we've gotten off on this, but it likely is not your hot start problem.

[dustman_stx]

Thanks for all the help DR. I really appreciate it. As for the hot start problem, is it normal to have LOTS of vapor(I guess it is a vaporized air/fuel mix- smells like gas) floating around inside the carb after it sits for a couple of minutes? As in, vapor pretty much boiled out when I took off the breather.

[george worley]

Just one last idea on your hot start trouble, does the demon carb use the same type of needle and seat as the holley ? I have had the little "O" ring seals on the needle and seat get worn or pinched and let fuel get past them. When that happens it acts the same as a heat soak problem. I have had to change mine a couple of times . I learned to lubricate the "O" rings with petroleum jelly before I install them to make sure they don't get pinched and go in smoothly. Also I was told to set the fuel level so that at idle the fuel was at the bottom on the sight holeand if you rocked the truck a little the fuel would just trickle out.

[dustman_stx]

Just one last idea on your hot start trouble, does the demon carb use the same type of needle and seat as the holley ? I have had the little "O" ring seals on the needle and seat get worn or pinched and let fuel get past them. When that happens it acts the same as a heat soak problem. I have had to change mine a couple of times . I learned to lubricate the "O" rings with petroleum jelly before I install them to make sure they don't get pinched and go in smoothly. Also I was told to set the fuel level so that at idle the fuel was at the bottom on the sight holeand if you rocked the truck a little the fuel would just trickle out.

Not sure about the seals. I unboxed it and installed it. I think I will lower the bowl levels again, though. I set them in the middle of the sight glass the other day, and when I noticed the vapor the fuel was at the top of the sight glass. It wasn't above, but it was at the very top. Wonder how full the bowls have to get to allow fuel to overflow?

[george worley]

I think that is high enough to cause it to flood.The fuel level should not change that much from running to shut off.Gas is running down in the manifold ,that's why you see vapors and smell fuel when it is shut off. A holley needle and seat can stand up 10lbs pressure and not pass fuel if its in good shape. Three things to try, if you have a rubber fuel line between the fuel pump and carb crack the line open a little and see if that stops it from flooding. BE CAREFULL and do this with the engine off of course. If that helps you have either #1 to much fuel pressure #2 needle and seat leaks #3 fuel level to high. Or if doesn't help you probably have heat soak. Gas boils at a lower temp. than water.

[DuckRyder]

I agree with that, I've always set it at the bottom of the hole so it just barely sloshes out if you jostle the vehicle...