As per subject. This is a Weber, but was hoping to not scare anybody off

Here's the deal: just replaced my vacuum advance pod because I was having big problems with timing and I assumed it was worn out. Turns out that was not the case.

So somehow, the vacuum port on my 38 Weber is plugged. I know this because the timing does not move when you plug in the distributor vacuum hose.

Hose is alright, by the way. The mouth suction technique does advance the timing.

I have another carb that I tried (a Weber 32/36), and it did advance the timing as well.

So naturally, with the non advancing vacuum advance, I'm putting along, with bursts of hesitation and just awful operation.

Anyone ever have a plugged vacuum advance pod? I sprayed carb cleaner into it, but nothing.

I tried putting some metallic wire in there, still nothing. Any tips?

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63 Plymouth Valiant V200 Convertible.
225, HEI, Super Six with 38/38 Weber, Electric Fans, Scarebird discs, FirmFeel front swaybar.

Are you checking the vacuum advance at idle or above idle? I ask because most carbs have a nipple for vac advance that's "ported" vacuum- that is, it has no vac at idle but builds vac as you open the throttle. I'd get a cheap vac gauge, hook it to your carb port & see what it does as you raise the rpm's.

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63 Valiant Wagon
225 - 4 bbl

The Webers actually aren't ported.

I checked this morning with a Vac Gauge, and I get about 5-8 at idle.

Like I say, my burn is that there USED to be no problem. Unplug the hose, set up the timing, plug in the hose and it advances 12-15 degrees at idle.

Now, plug in the hose and NOTHING.

This is just insanity.

Changed the hose, vacuum can is new (and can be advanced by mouth).

WTF?

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63 Plymouth Valiant V200 Convertible.
225, HEI, Super Six with 38/38 Weber, Electric Fans, Scarebird discs, FirmFeel front swaybar.

I believe the vacuum ports run horizontal with base then turn 90 deg down to get vacuum from plenums.

See: http://s785.photobucket.com/user/67dart ... e.jpg.html

Maybe your ports are plugged in the vertical portion, maybe pull the carb and see if these are plugged?

bg

New Idea: Would I get a working advance effect if I just plugged the port and instead hooked it up to the same manifold runner that my Vacuum gauge is connected to?

Seems like for the cost of a tee and some clamps I could put this stupid issue to bed.

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63 Plymouth Valiant V200 Convertible.
225, HEI, Super Six with 38/38 Weber, Electric Fans, Scarebird discs, FirmFeel front swaybar.

No!

You wanted ported advance or it will ping to death and get horrible mileage. You need to drill and tap a port above the blades, not below.....
You do not want any advance at idle......instead progressively kick in as the blades open.

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

Webers don't actually come with ported vacuum advance.

I tried running the 38 with a tapped port above the blades and it was unfortunately a total nightmare. Just doesn't work, frankly. A lot of sputtering and just bad backfiring.

When the port below the blades is working, it's a super smooth running carb.

Also, not to pump another Forum's tires, but this is a pretty good discussion on it Ported vs. Manifold Vacuum:

http://www.hotrodders.com/forum/ported- ... 51264.html

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63 Plymouth Valiant V200 Convertible.
225, HEI, Super Six with 38/38 Weber, Electric Fans, Scarebird discs, FirmFeel front swaybar.

You need ported port period! unless you have a computer or a way of slowing the vacuum at various rpms.
You never want to dump that much timing with a vacuum canister that early on a MOPAR engine in a street car. You want as much initial as you can (10 to 16 degrees) then a fair amount of mechanical (20 degrees) and the rest vacuum advance to come up to 50 to 60 degrees depending on your set up. Basically your controlling the vacuum advance with your foot! Burry the pedal and you got zero....let up and you get 12 to 25 inches. Mine idles at 19 inches so that would mean the vacuum advance would be full on! which would a constant ping......mileage would be horrible.

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

The problem with that discussion is that other manufacturers used different methods for acheiving their timing requirements (Ford's push or pull advance/retard mechanism...some GM vehicles used only manifold vacuum in the 70's...they didn't run so well)...Mopar engineers got their distributor right the first time and just took a while to tweak the curves until EI and smog came into the picture...for us it will always be ported switch for vacuum advance for the reasons that Ted discusses....you need to "light the fire" earlier in highway cruise situation, but don't need that much advance at lower speeds or at idle...this is icing on the cake so to speak, as it adds to the mechanical and static timing of the distributor itself...

A big block mopar with the large bores really needs to light the fire sooner to get the burn started across the bore...we have 2/3 that distance to go and 1/2 the displacement so what works for them
may burn the tops off our pistons...

-D.Idiot

I guess a lot of my issue here breaks down to the Weber setup, which does not use Ported Vacuum.

I guess it's difficult for me to "go ported" here just because of the fact that 98% of Weber carb users use what the carb comes with - i.e. NON-ported vacuum - and achieve better than OEM results. Naturally, the Mopar distributor may make a difference here.

I guess my issue with ported vs. non-ported is the fact that the main difference that I've seen with it (repeated again and again on the web) is that ported gives no vac advance at idle, while non-ported does.

Otherwise, they are the same setup!

Some interesting reading from http://www.forabodiesonly.com/mopar/arc ... 94481.html:

Now, to the widely-misunderstood manifold-vs.-ported vacuum aberration. After 30-40 years of controlling vacuum advance with full manifold vacuum, along came emissions requirements, years before catalytic converter technology had been developed, and all manner of crude band-aid systems were developed to try and reduce hydrocarbons and oxides of nitrogen in the exhaust stream. One of these band-aids was "ported spark", which moved the vacuum pickup orifice in the carburetor venturi from below the throttle plate (where it was exposed to full manifold vacuum at idle) to above the throttle plate, where it saw no manifold vacuum at all at idle.

This meant the vacuum advance was inoperative at idle (retarding spark timing from its optimum value), and these applications also had VERY low initial static timing (usually 4 degrees or less, and some actually were set at 2 degrees AFTER TDC). This was done in order to increase exhaust gas temperature (due to "lighting the fire late") to improve the effectiveness of the "afterburning" of hydrocarbons by the air injected into the exhaust manifolds by the A.I.R. system; as a result, these engines ran like crap, and an enormous amount of wasted heat energy was transferred through the exhaust port walls into the coolant, causing them to run hot at idle - cylinder pressure fell off, engine temperatures went up, combustion efficiency went down the drain, and fuel economy went down with it.

and

Anyone driving a street-driven car without manifold-connected vacuum advance is sacrificing idle cooling, throttle response, engine efficiency, and fuel economy, probably because they don't understand what vacuum advance is, how it works, and what it's for - there are lots of long-time experienced "mechanics" who don't understand the principles and operation of vacuum advance either, so they're not alone.

This from an auto engineer. Er, from GM. (I know... BOOOO!!!)

Anyway. Tinkering today, so I'll try the setup both ways and report back.

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63 Plymouth Valiant V200 Convertible.
225, HEI, Super Six with 38/38 Weber, Electric Fans, Scarebird discs, FirmFeel front swaybar.

Exactly...and that's how GM ran their distributors, none of it applies to how timing works on a mopar who used ported vacuum advance since 1960.

Page 2 of this post 2 years ago will explain:

http://www.slantsix.org/forum/viewtopic ... d&start=15

It all boils down to the need for a carb, or some way to get you a regulated vaccuum signal for the vacc. advance.

-D.Idiot

63valconvert,

Your mixing apples and oranges.....GM vs MOPAR.

If your car is a race car the Weber is fine. If you have a street car, then get a carb with ported vacuum and you will have a fun car to drive and get good mileage.

Your choice!

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

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63 Plymouth Valiant V200 Convertible.
225, HEI, Super Six with 38/38 Weber, Electric Fans, Scarebird discs, FirmFeel front swaybar.

If you are running a stock Mopar distributor that has a vacuum advance system, you need to run ported vacuum advance.

Period.

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Casually looking for a Clifford hyperpak intake for cheap.

Man, quit dancing around the issue. What are you really trying to say???

Well, ported is what I'll go with for the first tests, despite the inferior running conditions. We'll see what happens where it matters most - at the gas pump!

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63 Plymouth Valiant V200 Convertible.
225, HEI, Super Six with 38/38 Weber, Electric Fans, Scarebird discs, FirmFeel front swaybar.