Any Ideas

[samdotcom]

Hello everyone
I,ve got a 64, wildcat, 401, A/T ,rochester 4gc carb., and stock points and distributor.
My problem is that everytime I connect my vacuum, (below the carb) to the distributor vacuum advance, I get a serious idle problem. The points are set and the timing chain specs are all in spec. I also show vacuum pressure below the carb (manifold pressure) to be constant at 20 psi. New points, plugs, rotor, distributor cap, wires etc. All ignition equipment working.
No carb hesitation, backfiring etc. Just can't seem to dial in the distributor with the vacuum connected. Engine runs fine with vacuun open at bottom of carb plate, or when hooked to a vacuum meter.
Any ideas would be more than welcome. I'm guessing I've got a distributor problem but I forgot to mention that the distributor dwell variation is less than 2 degrees so I'm guessing the distributor shaft is ok.
I've also replaced the vacuum advance and it holds vacuum on and off the bench.
Once again thanks in advance.
Sam

[WildKitty]

Sam, I'm not that familiar with the 401, my 64 Wildcat has the 425.

I have a set of guages on the firewall (including the vacuum guage) I have it plumbed into the manifold behind the carb.

Maybe try hooking the vacuum guage there and the distributor from below the carb. see if the guage is still a steady reading. my guage levels off at 20 once she warms up.

is your hose between the carb and dist new?

keep us posted
Butch
64 Wildcat 445
64 LeSabre 310

[samdotcom]

Thanks for your time....

I,m using a test vacuum meter connected to the base of the carb., where the distributor vacuum advance line would be normally connected to the distributor. I've connected the meter there for two reasons.
1. I wanted to set the timing correctly and
2. I wanted to make sure that the carb was tight with no leaks.
At least this way I can rule out an intake manifold gasket leak; or a carb., vacuum leak.
Once I block this line from below the carb with a meter or a screw with a new rubber hose line, the idle cleans up and the engine runs fine. The moment I connect the vacuum line back to the distributor advance, then the idle becomes very rough. I'm guessing distributor problems? Maybe mechanical advance? No idea! Just hate to have to purchase a rebuilt ditributor to find out if I'm right or wrong again.

Thanks again. Hope to hear from you soon if for no other reason it's great to talk to someone with the same make and model problems.

Sam

[Airy Cat]

The hose for the distributer is connected at the front of the carburetor, not the rear.

[Bob]

I do not know if a '64 Wildcat should or should not have vacuum to the distributor at an idle.

So with that in mind, most of these cars do not have vacuum to the distributor at an idle. The carburetor must be moved off the idle to get the vacuum. If you have vacuum at an idle as you say, when you plug the line in you are drawing in 12, 16, ?, of timing at an idle. Before you proceed, first determine this.

Are you running an original or aftermarket carb. You may find another port that has no vacuum while at idle, but has vacuum as soon as you increase rpm.

[BigRivy]

Running full advance at idle should not be a problem. I've run all my Rivieras, '65's to '72's, that way for years. The next thing I would check, and this is just a guess, is the breaker plate. Take the cap off the distributor and stick the hose that runs to the vacuum advance in your mouth and suck on it and watch the breaker plate move back and forth and see if it changes the relationship of the points contacts or just generally moves around and changes the relationship of the points rubbing block the the 8 sided lobe on the distributor shaft. Obviously it will advance it, but look for changes in distance closer and farther from the lobes. If it is loose it needs fixed. This is a real common problems on Fords, but can happen on GM's. Did you replace your vacuum advance to try to fix this problem or did it show up when you replaced your vacuum advance? Not all advance canisters have the same amount of travel. How many degrees advance are you setting it to at idle, with the advance unhooked of course? I guess you could also check the breaker plate by running the engine with the port on the carb plugged and apply vacuum to the advance from an outside source, use your mouth or a hand held pump, and see if that causes it to run rough. If it does run rough that would prove that the problem is in the distributor.

[telriv]

You have TOO MUCH initial timing, I believe it should be 2 1/2*, or the vacuum advance is giving WAY too much advance. If I remember correctly on '64's with a single carb. the vacuum for the vacuum advance was FULL vacuum, not ported.

[WildKitty]

I was also going to suggest blocking the port on the carb and sucking on the vacuum advance tube to see if there was a change. if you havent thrown it away, and if it holds vacuum, putting the old one back on

I bought a new one for the 300, not because it doesn't work, but because the old one wouldn't clean up. I'd hate to think the replacement is that different in pull distance, but I guess that can be resolved by turning the dist a bit.

[samdotcom]

Hi guys, sorry for waiting so long to answer but the kids keep bringing their car, trucks etc. over to the house for "good old dad" to fix. you know how that goes(smile).
Anyway..............
To answer a few replies to everyones thoughts, I thought to update everyone on what I've done so far, hoping this might help answer some questions and hopefully create some more ideas.
I'm still not certain that I don't have a problem with carburetion or vacuum leaks at other places, BUT............I have run a vacuum check at the
manifold BUT........I also have a steady 20 psi readingbelow the carb plate.
All other vacuum connections seem to be tight. I've even ran a propane tank test all around the base of the carb and the the intake manifold with no changes in the idle.
So..................
I've removed the distributor, cleaned and dis-assembled the unit and checked for good connection contacts from the points and the vacuum plate.
Checked the shaft for out of round conditions, (good so far).
Replaced the vacuum advance unit with a new vacuum advance.
Put the old vacuum advance back in and measured the pulling distance of the old advace compared to that of the new advance and found them to be almost identical when 20-25 psi vacuum is applied with a vacuum gun. Keeping the NEW unit.
Replaced the points and condenser with a new set.
Examined the oil pump gear and found (not to much wear that I can tell).
Checked the mechanical centrifical weights. (They seem to be operating normally, if not a little weak for the spring tension.) still acceptable as far as I can see.
Checked the shaft lobes for wear. They all seem to be making good contact with the points at each lobe. Good spacing on all contacts.
Will once again replace all vacuum hoses with new tubing.
I'm about to put the distributor back in tonight or tomorrow and see what, if anything changes.
Thank-you one and all for your comments so far. I'll let you know in the next 48 hours how we're doing.
Wish me luck.
Sam

[WildKitty]

Sam
let me throw this out there;

do you know if the carb float is right?

when I rebuilt the Carter, I forgot to check the float level and she would flood when I pumped the gas. I didn't notice it flooding until I installed the lectric fuel pump.
the float level should be 5/16"
Butch