Engine Miss: Part Deux - Distributor

I have been chasing a pretty radical miss on my motor the last couple weeks, and I have done everything just short of tossing the distributor out the window.

Today, I disconnected the vacuum advance and the miss stopped. Is the vacuum advance canister replaceable? Or should I just call Dave?:Brow:


This is what I have done to locate the miss:

- Resealed intake due to vacuum leaks
- New plugs
- new MSD 8.5mm wires
- new cap, rotor, points, coil
- carburetor rebuild


Jeez, when I get this figured out, I'll be set for a couple years:grin: :beer

 

They must be available

Cause I had a new one on mine when it came back from Dave.:TU:

 

I'm drooling:Brow:

I've decided that sometime this winter I wantto send my distributor out to him for a conversion....I haven't got any idea what it costs though. hmm.....Dan, you must have an idea:grin: :TU:

 

I doubt you have a problem with the vac advance can. Your problem is probably in the dist. It's only job is to turn the breaker plate. (Unless its leaking and you stop the leak by disconnecting the vac line and plug it.....but that would have to be one heck on vac leak and your eng would have to be soooo lean already and pulling vac from one runner on the intake manifold and the chance of that is so out there that....whatever).

When the vac advance turns the breaker plate in changes something in the dist. Could be a bad wire going to the points. The breaker plate could be cocking and causing the dwell to change on different cylinders.

The other thing that could be happening is you have the ign timing too far advanced and the addition of the vac advance causes it to fumble around.

Just to make sure, you did say miss and not hesitation/stumble. I get customers coming in all the time confusing the two.
Is it only on accel?
Is it at idle?
Is it at cruise?
Do you have your vac adv hooked to manifold vac or ported?

Let me know

 

Vac advance is connected to the carb fitting that the air cleaner is attached to - full vacuum. Vacuum on that line is 20-21 inches.

The miss is at idle and up to 1500 RPM or so. It almost sounds like I have a lopey cam when it's sitting there. The car also runs rich....this appeared when the miss came about.

Timing is set to 12* initial...and holds steady, but I didn't check it with the vac advance connected. So it could be fumbling around when I hook it back up.


It is not a stumble or hesitation, as I've had lots or problems with my other car with that. Nose dives off the line are not fun.


I'll take a look at the wire going to the points tomorrow...but wouldn't it be missing when I disconnect the vac advance if that was the case? It runs fine without the vac advance connected.

Let me know..:beer

 

Here's the lowdown on Dave's conversion. $175 for the works, $135 if you use an MSD box. make sure you use whatever the latest coil he recommends.

 

Any idea on turn-around time?

 

A coupla weeks, but he was having trouble with his component supply when he did mine. I also think it depends greatly on how busy he is. Give him a call and ask him. His number's on the site.

 

Here's Dave's answer to the coils he now recommends:

Jeff,

Yes, the newer Accel's are falling like flies. On each of those Accel's you have is the crimp at the top of the cannister all the way around the full diameter at the plastic top, or does it have segmented crimps, short crimps then rasied metal between them??

The full crimpers are Accel's made in Taiwan, and they are the bad guys. The segmented ones were made here in Indiana, and are the good ones to use, but they aren't available any more. I didn't know this until about five weeks ago.

Suitable coils now are, black, NAPA IC12 (NOT the IC12SB), Crane PS20, and chrome, MSD 8200, Crane PS40.

 

"I'll take a look at the wire going to the points tomorrow...but wouldn't it be missing when I disconnect the vac advance if that was the case? It runs fine without the vac advance connected."

The wire going to the points is fixed at the dist housing and fixed at that points. When you move the breaker plate (as the vac advance pulls on the breaker plate), the wire moves. If the wire is worn bare, only take one tiny spot, and touches any thing, it can cause a miss that can either cause the engine to die, or touch and cause engine to try to die, but, as engine is slowing and vac changes, the wire moves away from the short to ground and eng continues to run and then try to die again over and over and over.....

Anyway, sounds like you have your timing too far advanced when you hook up the vac advance. Take a look at your timing when it's hooked up. I like to run ported vac on the dist. The port on the main body to the drivers side of the fuel inlet on a q-jet is usually the spark port.

 

Adam - Dave will want you to pick up a Crane adj. vacuum advance unit anyways (unless you have him supply it). So...if you wanted to pick one up now to try, at least you won't be buying anything he wouldn't want you to use.

 

Vacuum advance is giving too many degrees of advance, needs to have a simple stop made and fitted to the mouning bar of the vacuum advance. I have three pics if you are interested.

Yes, the added timing will cause the jetting to lean way out, and that is the reason the vacuum advance needs to be restricted.

I forgot, this e/mail system here is like beating two sticks on a tree trunk in eht jungle and isn't user friendly for sending pictures, so, please send me an e/mail tomorrow and I'll send you the pics on how to stop the advance down.

sparkman451@earthlink.net

 

I have put stops on many dist's. They work just fine. I have had less trouble with stops than adjustable vac cans.

 

Why would you hook vac advance up to full manifold vac. Your intial timing with that hooked up is probrably around 30 degrees or so. Advance should be hooked up to ported vac. Hope you get it figured out.

 

Just to clarify, I don't recommend throwing a stop on your vac adv unless you need it because you altered the engine enough where the stock tune up specs no longer apply. If you engine is remotely stock, and the adv can doesn't pull any further than the stock one that the car left the factory with, then you don't need to alter it.

 

hmmm....never realized that one...

I learn something new every day:gt:

I'll plumb the advance to ported vacuum like suggested here...



Dave, sending you mail:TU:

 

Problem solved...after more pain and suffering than ever.

Vacuum advance was plumbed to full vac and not ported vac.

I switched it to ported vac, and it purrs like a kitten!:beer


Thanks for all the replies and helpful suggestions!


I realized what I did wrong...when I installed my guages, I had to get rid of the vacuum tree on the manifold, and I just basically plumbed all 3 of the lines together. Not the wisest idea I've ever had...ou:


Dave, got your email with the pics...thanks:TU:

 

Adam, don't feel bad A lot of people make the same mistake. You would see it right away with a timing light of course. For some reason, some people do run it to manifold vac purposely. I don't know why though.

 

Does the engine have an EGR valve on it?

No.

Then it needs only 8 to 10 crankshaft vacuum advance degrees, NOT the 20 t0 25 they usually add when plugged in, and to be connected to FULL MANIFOLD VACUUM SOURING, NOT PORTED.

Once again, the setup you have is incorrect, even though you got it running better, all you did was stop the vacuum advance from operating correctly and took that potentially very helpful vacuum advance and rendered it a moot point.

You can do better by restricting the degrees down and changing back to the correct vacuum for your system. The only problem you had was too many degrees added, you had it on the right port to begin with.

One thing everyone doesn't realize about vacuum advance is, they are aftermarket incorrectly built for ported vacuum sources and EGR systems levels of timing given, even though most of them were originally done for full vacuum engine setups, having a rubber stop on the pin, which the cannister manufacturers seem not to include with the new advance. So......people out of the know, just ported vacuum it, which is wrong, then state it worked better with ported vacuum. Sure, as long as the vacuum advance is rendered moot by NOT being set up right, ported vacuum advance will not do anything but confuse most people, and not restricting the vacuum advance for full manifold vacuum also feeds the no-knows that say it doesn't work.

If it ain't set up right, all it does is feed the lack of info about how to properly set up and use it. I've proved this fact over and over again, on all kinds of engines utilizing their vacuum advances incorrectly, on ported vacuum.

 

Dave, should have seen the trouble I had arguing with the last mechanic who scoffed at the thought of using full manifold vacuum. It came to the point where I rang back half an hour later and made up some excuse about being too busy to bring the car in and left it at that.