Ported Vacuum??

[Deleted User]

I've recently put the Wasp back on the road with a new head gasket. And honestly, doing some tuning above and beyond what I had done with it before. I had driven thousands of trouble free miles with it before the gasket failure, and pretty much left things alone up until that point. It ran really well. The only thing I had messed with was the metering rods in the WGD carburetor.



But now, I've run into something I wasn't prepared for and has me scratching my head.



Were Hudson distributors supposed to be vacuum advanced by ported vacuum, or direct manifold vacuum?



I ask this because the WGD carburetor on my Wasp, acts like the vacuum advance hookup is indeed ported vacuum. Meaning, I get practicly no vacuum reading until I barely crack the throttle - then it goes to slightly over 20"Hg of vacuum. I retimed it as if it were ported, and the dang thing runs like a clock. With the butterflys closed in the idle position, I have about 5" Hg.



This is in opposition to the Super Six, running the Edelbrock 4 barrel. I have it hooked up to the direct manifold vacuum port and have its intial timing set with a vacuum guage. Its running about 8 degrees advanced at idle, with the vacuum pulling another 3 degrees when hooked up. The total initial timing at idle on that beast is 11 degrees advanced. No pinging or detonation as of yet, and its been leaned on fairly hard - hard enough to have pinged.



I have the option on the Edelbrock to set vacuum advance by either ported or direct manifold vacuum.



Mark

Unknown

Originally, the source of distributor vacuum was ported.

Park_W

Mark, note that Hudson's recommended basic timing setting of TDC (at idle, so no mechanical or vacuum advance in effect) was based on 80 octane fuel. I'm running my '51 Hornet about six degrees advanced, and not only is there no problem with ping, but it's much more responsive to throttle and gets considerably better mileage than if set at TDC. And yes, as Dave says, the Hudson carbs' vacuum port for spark advance is "ported vacuum," i.e., no vacuum there at idle speeds.

[Deleted User]

Thanks for the responses!



The confusion and reason for the question was the manual I have stated that you adjusted the timing with the vacuum advance disconnected, which led me to believe it was full manifold vacuum. I guess it advised a disconnect to be doubly sure absolutely no vacuum influence was present at all. Even at 5"Hg, the vacuum canister actuates at 8"Hg - which is getting pretty close together.



Now I know better.



I run the 92 octane fuel in the '49, which would explain why I'm getting away with the total @ idle of 11 degrees. I'll change it back to the ported vacuum and see how that goes. Its running good now, but I've not tried it on the ported vaccum since working out some of the carburetion bugs etc. What I was attributing to a minor acclerator shot bobble - is probably a momentary bad timing situation.



Thanks



Mark

[Deleted User]

Mark,

I guess I need to look at this on my 50 Pacemaker since I am using

the Edelbrock AVS 650. Maybe this is the reason I am getting the

momentary stumble like I was telling you on the phone sunday.

If you remember I am running the clifford head on a stroked 308

but have always run 93 octane gas.

What is the total advance you are running with the mechanical

added in? I seem to be getting about 6 degrees vacuum and

around 12 degrees mechanical out of my distributor. (Late sunday

afternoon I fired her up and double checked these figures.) I really

could not tell which rpm its all in by but sounds like more than 2500

rpm going by ear.

I have tried several different initial settings but right now its at

12btc at idle with the vacuum line plugged. The total appears to be

right at 30btc which I know is way too much but it does run very strong

with no ping period. The only side effect I have seen is a little hotter

running temp on the gauge by 10 degrees max.

Several of the racing Hudson nuts have told me that 24 degrees

total advance was optium so I do need to retard this some.

I did use both of the vacuum ports as shown in the Edelbrock

manual but I do not remember if the car drove different.

I also ran it at 8 & 10btc and the stumble was more pronounced.

Looks like I really need to pickup a good vacuum gauge to check this

and tune some more. Man I would trade my ex-wife for a good old Sun

distributor machine!

Can't wait for spring to get here so I can take her out and flog it some

for test data. Got to get ready for racing season!

PaceRacer50

Unknown

PaceRacer50 wrote:

Mark,

Man I would trade my ex-wife for a good old Sun

distributor machine!

Can't wait for spring to get here so I can take her out and flog it some

for test data. Got to get ready for racing season!

PaceRacer50

Do you mean your Hudson, your ex-wife or both? :rolleyes:

[Deleted User]

PaceRacer50 wrote:

Mark,

.

What is the total advance you are running with the mechanical

added in? I seem to be getting about 6 degrees vacuum and

around 12 degrees mechanical out of my distributor.



I have tried several different initial settings but right now its at

12btc at idle with the vacuum line plugged.



Several of the racing Hudson nuts have told me that 24 degrees

total advance was optium so I do need to retard this some.



I did use both of the vacuum ports as shown in the Edelbrock

manual but I do not remember if the car drove different.



I also ran it at 8 & 10btc and the stumble was more pronounced.

Looks like I really need to pickup a good vacuum gauge to check this

and tune some more. Man I would trade my ex-wife for a good old Sun

distributor machine!



Can't wait for spring to get here so I can take her out and flog it some

for test data. Got to get ready for racing season!

PaceRacer50

I believe the total mechanic movement is 16 crank degrees / 8 distributor degrees. Its not much. If you look on the arm of the vacuum unit, it has a number stamped in it. All the ones I've seen for the Hudson are stamped "3.5", which means it has a 3.5 crank degree movement. Some mopar vacuum units have different numbers, and consequently - different degrees of timing movement.



So, the total advance on my 308 right now would be. 8 btc initial + 16 mechanical + 4 vacuum (thats the vacuum I'm actually reading with the timing light, dang close to the 3.5). 28 degrees total. Like yourself, I have no idea at what rpm its all in. I set the initial with a vacuum guage per a thread here. Advanced it until it read maximum vacuum at 21" Hg - then backed off the timing until I lost 1" Hg. When I put the timing light to it, it was at 8 btc. If you take the vacuum advance out at WOT - I'm dead on 24 degrees total.



Of course, when I hook up the vacuum advance to the full manifold vacuum spigot - it jumps right to 11-12* btc at idle. So, right now for all practical purposes, I am timed this high at a running idle. Cranking at 8 degrees btc and running at 11-12.



Looking at the Edelbrock carb with the idle screws in front of you. The ported vacuum spigot is on the left, full manifold vacuum on the right.



I have no idea what the numbers on the Wasp are, it is currently set by ear and seat of the pants. I used a little motorcycle battery to power my timing light (The cars are 6 volt and that causes all kinds of problems with a timing light - makes the flash slow and inaccurate) and its kaput.



Interesting stuff. I had the vacuum advance hooked up to the ported vacuum of the Edelbrock when it first fired up. The first on road trials were done this way - and I had a horrendous stumble. I've come a long way since then in tuning it, probably enough to do a good ported vs. non-ported test.



Of course you know, the Edelbrock fueled engine is the candidate for the McCulloch. Per the discussions we were having on the phone about above venturi and below venturi pressure differentials, I'm struggling with which side of the venturi I'd want my timing to be hooked to?. I actually need a vacuum canister with about 8-10 degrees of timing movement for the McCulloch.



Great discussion.



Mark

[Deleted User]

Dave53-7C wrote:

Do you mean your Hudson, your ex-wife or both? :rolleyes:

I'd love to have a good distributor machine.



I'm afraid thats way down the list, unfortunately.

[Deleted User]

Mark,

Actually one more flog of the ex-wife would be fun but the constant nag'n

just isn't worth it!

After read your comments above on which vacuum port is manifold vs ported

on the Edelbrock I have mine in the manifold port. I did go out in the garage

last night and had a much worse stumble when in the ported vacuum port

on the carburetor.

I did not pull the cap off the distributor in the 50 but my extra distributor I

have had 3.5 stamped into the vacuum advance arm. Its getting pulled appart

tonight, cleanned and all the parts inspected. Once its ready to go back

together its getting the Petronix conversion.

Usually on the drag racing engines we build they always get the mechanical

advance locked out and the vacuum advance removed. This way we can

dial in the exact advance we want as initial advance thus not having to

worry about the curve. So far this has worked out really well and not caused

any starting problems but I have not done this on the Hudson yet.

That is what the extra distributor was orginally for.

On the supercharged setup I had the best driveability leaving the vacuum

advance hooked up exactly the same as without the supercharger. I have

used the MSD 6BTM units so I can pull out timing when on boost. This allowed me to pull out up to 3 degrees of timing per pound of boost. Works

real good because you can talor this ammount of retard based on the octane

of gas you are using. That and it sure beats trying to run one of the old

school vacuum cansiters with the advance-retard like the old Corvair turbos

had.

Like I said a distributor machine is needed now! Too bad the funds are

needed elseware.

PaceRacer50