Timing Question for Those with Carbs Options

[Ansbacher]

My 74 2.0 with dual Dell 40s seems to run best at the following timing advances -

13 Degrees at 900 Idle RPM
37 Degrees at 3500 RPM

Are these numbers reasonable for a carbed 2.0L ? I do not know if the previous owner changed the cam when the fuel injection system was removed. I would be interested in hearing what others are running for advance with similar setups.

Thanks all,

Ansbacher

[stugray]

37 deg at 3500 is reasonable.

What is your compression ratio, what gas do you run?
What distributor do you have?

[Ansbacher]

I have never pulled the dizzy, and cannot see the label in the position it is in, so don't know what it is. Don't know my compression ratio. I run non-ethanol 89 octane gas.

[r_towle]

In my opinion 37 degrees of advance on a stock motor is a bad idea.
27, maybe as high as 30 would be as far as I would go, ever ever.

[Ansbacher]

The car will not run at 27 degrees. A while back I started a thread questioning the validity of my timing marks on my fan for that very reason. Then I read a lot of references that stated carbureted 914s need a much higher advance than a stock car with FI. Listening to both sides of this issue has me worried again. My temp gauge does not exceed much past the halfway point, even on a hot day here in Florida, so I kinda figured I was not advanced too drastically. Wish I could get a handle on this.

Ansbacher

[r_towle]

I recall that thread, but did you ever remove the fan and properly mark it?

[Ansbacher]

No. It seems to have the factory white and red marks in the proper places, and everyone said the fan could not be mounted in the wrong orientation, so I am assuming the marks are good.

[r_towle]

How do you know you are at 37 degrees advance?
Is the fan marked or are you using a gun that can read it and display it?

If it's the gun, I would get an old school one with no adjustment and test it again.

[Ansbacher]

I have both types of timing guns. The dial-in type tells me I am at 37 degrees using the white TDC mark and the oild school one shows I am approx. 10 degrees beyond the red 27 degree mark- voila 37 degrees.

Ansbacher

[colingreene]

That seems like way too much.

[Mike Bellis]

Forget the marks and time it with a vacuum gauge. Connect the gauge to the engine and set the timing for maximum vacuum at idle.

That's how we did it in the old days when timing marks were gone. An "inches of Water" gauge is best for this.

[Ansbacher]

Afraid measuring timing with a vacuum gauge is Greek to me. Would not know where to begin. Sure wish other owners of carbureted cars would chime in with their advance numbers, so we could get a consensus on this. Anyone...???...

Ansbacher

[stugray]

Mine is set to 34 degrees and I have some room left to give it a little more.

I run pump gas (91) with 9.5:1 CR, 1 mile high with a Mallory Unilte Dist. & MSD.

34-37 degrees @3500 is what many of the vintage guys are running.
Lower altitude (more air) and you should back that off a bit.

[Ansbacher]

Stugray - Your numbers are encouraging. Question...if you set your car to 27 degrees (red mark) would it stumble all over itself and barely run?


Ansbacher

[Mike Bellis]

Afraid measuring timing with a vacuum gauge is Greek to me. Would not know where to begin. Sure wish other owners of carbureted cars would chime in with their advance numbers, so we could get a consensus on this. Anyone...???...

Ansbacher

Connect gauge to vacuum source.

Loosen distributor clamp.

start engine.

turn distributor (back/forth) until maximum vacuum is read on the gauge.

tighten distributor clamp.

disconnect vacuum gauge.

Go drive.

Easy! (IMG:style_emoticons/default/smile.gif)

[Ansbacher]

Thanks Mike, you have taught me something. Can't wait to try it.

Ansbacher

[r_towle]

Stugray - Your numbers are encouraging. Question...if you set your car to 27 degrees (red mark) would it stumble all over itself and barely run?


Ansbacher

Vintage guys, and Stu are using higher compression motors....
Possibly different Camshafts.

You, setting your timing that far advanced, have created a potential of running too lean and buring up a piston, or buring a valve.

Rich

[Bulldog9]

Ah, timing............ one of those things I haven't even thought about yet, but need to.

When I rebuilt my motor, I was thinking enough to paint the mark red when I restored the fan, and cleaned up the timing notch but that's it. I assumed I would set the engine at true TDC, maybe break out the protractor to set close to the 27 BTDC. Then break the engine in, then set the timing at 27 BTDC at 3500 RPM with a timing light, then sync carbs, set mixtures, set timing again, etc.

I figured when I bought a light, it would be one with a tach and that you can advance or change the light timing to keep the notch and line. i.e. set the light for 0 and when you move the distributor to line up the timing mark you will be at 27 BTDC. Want to go 30 BTDC, set the timing light with a +3, want to go to 24 set the light to -3. Does this make sense, or do I have too many damaged brain cells? (I only had 2 Guinness to celebrate my ancestry yesterday) (IMG:style_emoticons/default/beer.gif)

Granted, I haven't set the timing on a car since......... well, you don't want to know but it is at least 20 years...... Reading this, I realized that I may be wrong in my assumptions

I am running Dells, and a Pertronix Billet Distributor.

[stugray]

With a variable timing light, I set it at 34 degrees
Then I use the TDC mark on the flywheel and not the oneS on the fan.

[Bulldog9]

With a variable timing light, I set it at 34 degrees
Then I use the TDC mark on the flywheel and not the oneS on the fan.

Not sure this is doable on a 912E. Any reason you do it this way as opposed to off the fan?

Is my assumption that setting the light for '0' advance and aligning the mark will put me at the correct 27? I'm sure that with all the modifications, bigger cam, hotter spark, mechanical advance, carbs bump in displacement and compression the timing needs will change, but am just looking for a starting point.

Thanks!