Weber Carbs, timing advance

An hour on a dynomometer seems the most straightforward way to sort out such an engine. Before arriving, inform the dyno operator what you're aiming for- driveability, mileage, acceleration etc. and bring a handful of springs and weights for your particular distributor, and maybe a good timing light. Marking the flywheel thru the bellhousing opening and timing off #8 cylinder can simplify setup if your firewall upholstering has not been cut. I recommend always carrying a 5 lb gaseous fire extinguisher for the inevitable Weber carb fires. BTW, I LIKE vacuum advance on street cars and Ford (maybe Mallory, too) vac adv is easily tunable with a rubber connecting hose.

So even though you're focused on the ignition, carb issues will certainly obscure any such results and the darndest things affect how they react. Webers tend to split issues: either lots of power and mileage in the 10-12 mpg range, or decent mileage & driveability and no power. If you've been running Webers for awhile, you know there are 5 jets and 2 air bleeds per barrel  in most Weber carbs, and it's easy to get lost. Fuel & ignition problems have much the same symptoms. If you're lucky, the 'mature' dyno operator may be familiar with Weber problems and have a collection of jets etc. Maybe only an hour on a dyno is optimistic.... Good luck.

You need to set it as Bosswrench suggested. On a dyno. That is to say, pull the engine out and put it on a  dyno. Even so, that's gonna' be off a little because of the dyno headers. They are going to be better then what you can get into the car.

I can tell you what my settings are but unless you are running the same setup, it doesn't really matter.

A vacuum advance can give you a few more mpg at cruising but you need to be plumed for vacuum into a common vacuum plenum, which you are not. Considering the intake that you are using I wouldn't consider putting any holes in it and unfortunately 48ida's don't have any vacuum ports.

I can tell you that I am running 15 degrees initial advance with 35 total. It's idling at about 800rpm. There is a little bit of a contradiction to that in that the aluminum heads not only don't need that much total but they don't even like it. Generally 33 to 34 is as much as they need. The tip in response is much better in the 14-16 degree range. You clearly can feel the difference between that and say 10-12 initial.

Iron heads are different with total advance and your actual compression ratio will affect that.

The contradiction comes in because of the Webers. That set up likes as much advance as the fuel octane will allow. 36 total is about right for them on iron heads.

I found that running on premium pump gas, about as fast an advance the fuel octane can handle is all in by 3,000 engine rpm. You might find 3,200 a little better.

The days of being all in by 2,000 rpm are done and gone unless you want to run on pure 106 leaded racing gas.

Oh and Bosswrench is also right about setting the jetting and the advance together. There are a bunch of settings that will run fine with the Webers all the way down to 125f mains and all the way up to 170f mains but the advance rate changes as do the plug heat ranges so when you do this it's kind of like one of those one man bands playing the drum, a wind instrument and the cymbals between your knees?

Thanks for the backup, Doug- its been awhile since I played with Webers. If I ever get my enthusiasm revved up again and finish my home-made side-draft intake manifold for a set of brand new 48 DCOE carbs, I will definitely be calling you.

On IR vacuum advance, I found that 'prettifying' the motor with unnecessary AN lines (rated at 3000 psi burst pressure) is counter-productive. Using a plain 1/8" ID rubber hose from the Weber intake to a dizzy vac adv worked fine, while 'other' plumbing I tried gave radically different results. I can only assume my 18" long rubber hose acted as a damper for the IR intake's violent pulsations, while more rigid lines faithfully transmitted every pulse and confused the mechanical advance mechanism. Ultimately, I found only one (1.0)  hose was necessary.

Gary Hall always insisted that only one throat was necessary even to operate the power brakes.

I don't get the same results.

I'm plumbed into the mounting flanges of the intake manifold which is enough volume of vacuum to operate a vacuum gauge normally, it still isn't enough to operate the brakes. I use a Compcams vacuum pump which yields something like 22 inches. The problem is it's noisy.

When it comes down to it a vacuum advance really isn't necessary and a mechanical advance like on the 427 and 289hp Fords is fine.

I've found that 140f/160a works very well for both economy and performance. You can run that proportion way up to 170f mains and continue to gain power.

I've arrived at the combination by trial and error over 30 years, not on a dyno but if someone wants a quicker answer surely a dyno is the intelligent way to go. Why believe me? I can't possibly be right?  I wouldn't be surprised if it made me look like the village idiot but I'll stand by my current conclusions.

I also discovered that I notched the rear decklid too quickly and that it will clear the rear carbs without notching it.

I also discovered that the fuel plume will stay inside the stacks if you use a 5" tall stack.

Inglese had the side drafts on his 66 GT350 when he blew it up in front of the ice cream store. It has a little more room under the hood to clear then a Pantera does but you might want to put some type of rpm limiter on the engine. I don't think it will like 9,000rpm?

You're welcome to call on me anytime but I noticed someone using the term "batshit" lately in description? So I adopted the motto and had some t-shirts made up. Makes people keep their distance so works better then pepper spray.

@panteradoug posted:

You need to set it as Bosswrench suggested. On a dyno. That is to say, pull the engine out and put it on a chassis dyno.

???  How do you run an engine on a chassis dyno ???

But seriously; one of the issues Weber (or IR EFI) owners face is, you'll get the intake perfectly dialed in on the engine dyno, then you have to take apart the linkage and perhaps even remove the carbs/throttle bodies to lift the engine back into the car. I had bracket made that allows me to lift the engine, with ZF attached, back into the car without touching the throttle bodies or the linkage.

Also, when you have your engine tuned on an engine dyno, there's no reason why they can't use your headers. In fact, I had my engine dyno tuned with the full exhaust system for some of the "pulls", just to see how it affected things. Luckily, it didn't!

Dear David,

        Slightly off topic: nice engine, but very impressive "engine lift hook". 

                     Warmest regards, Chuck Engles

@davidnunn posted:

???  How do you run an engine on a chassis dyno ???

 

FAST! Of course. 

IF you can run with your headers and exhaust, that would be excellent.

I can lift without messing with the linkage. Just the main throttle cable gets disconnected.

Some good information was provided here.

I'm no longer interested in pulling the motor for a proper dino test, those days are behind me, but I like the car to run as good as it can with my Weber setup and a new mechanical advance only Mallory dizzy. I like the Mallory unit because it's small and easily fits under the screen. It also comes with a number of springs, providing six different advance curves. the lightest springs show all in at 2400 rpm. The stiffest springs are all in at 5500 rpm. Then there is a matter of the advance stop bushing allowing a good range of rpm options. I'm playing with the options, but access to the dizzy is a pain.

I also use a vacuum pump for my brakes and it works very well. Yes. its a bit noisy on startup but once the motor is running it gets drowned out by a better noise.

@tomkuester posted:

Some good information was provided here.

I'm no longer interested in pulling the motor for a proper dino test, those days are behind me, but I like the car to run as good as it can with my Weber setup and a new mechanical advance only Mallory dizzy. I like the Mallory unit because it's small and easily fits under the screen. It also comes with a number of springs, providing six different advance curves. the lightest springs show all in at 2400 rpm. The stiffest springs are all in at 5500 rpm. Then there is a matter of the advance stop bushing allowing a good range of rpm options. I'm playing with the options, but access to the dizzy is a pain.

You should be able to find a shop with an old SUN distributor machine. They put the distributor on it and can set it to your specs.

For the street you want the total advance in for where you would be cruising. That is probably around 3,000 to 3,200. Often the rate of advance is arrived at by using a combination of springs like one heavy and one light which theoretically puts it in the middle somewhere.

I have a Ford Motorcraft distributor in mine with the small cap and it fits perfectly fine. The limiting factor is actually in this case the intake manifold which only considered fitting the small cap. The large cap will not fit between the carbs/runners.

There isn't anything wrong with the Mallory but it is a little bit different of an animal.

You can try the lightest springs and see how the engine runs with them. I think it will ping bad and secondly, the thin light springs tend to wear out rapidly and stretch to the point of not returning to zero. Ask me how I know?

The aftermarket distributor springs are not good quality. The Ford's you can't kill. I had a Mallory and an Accell. I couldn't keep advance springs in them. That's why they got replaced. No other reason.

Fortunately or unfortunately, Ford distributors and ignitions are the most reliable.

I have driven my Pantera about 700 miles a year, or 28000 miles in the last 41 years. Hopefully the lighter springs don't give me issues too soon, but they are easy to change. Thank you for your thoughts. Tom