Engine Vacuum Question (Timing, Carb Air/Fuel Mix) Anybody?

[Anonymous]

I bought a vacuum gauge so i could check for max vac on the carb. So the car is in park and the vacuum gauge read 18 Hg so i turned the screw until i got 20Hg and thought well that was easy.

So I got another person to sit in the car while i took some readings of the gauge, and i asked them to put it in Drive, and the gauge dropped down to 17Hg, and on the gauge it reads Late Ignition Timing. Well then, so thats my problem and question...

So is setting the timing the solution to my problem? Will turning the distributer fix it? I was gonna turn it, but where is the screw that hold it in place? But is this even the right way to fix it?

Neddle Readings:
Park: Steady; 20Hg
Park, Reving Engine: Fluctuates when step on to around 17Hg
Park, Steady Rev: Steady; 21-22Hg
Drive: Steady, 17Hg
Drive, Rev Steady: Steady; 20-22Hg

Thank you all very much who reply.

-Bryan

 

[Anonymous]

I am a little lost at what the problem is. Those numbers sounds like decent vacuum to me. Are you saying that the vacuum gauge has some comments on it in addition to the vacuum readings? If so, are you concerned that it says "late ignition timing"? A vacuum gauge cannot account for all of the variations in engines out there to make specific assessments like that. It could be timing, valves, vacuum leaks, cam design, carb tuning etc that is affecting the vacuum. So I do not know why they would print one particular cause on the gauge.

If you want to adjust the timing, the distributor hold-down bolt is at the base of the distributor. Adjusting the timing may indeed increase the vacuum. If it does, and your test drive does not reveal any pinging, then your engine should be running more efficiently.

 

[addo]

I know that style of gauge. They also perform other functions. They have a series of "typical" diagnostics printed on the dial. I realise it may be a furphy in this instance, but consider how many people "go stampeding towards the carburettor" (to paraphrase John Cleese) when the engine's a little off-perfect.

 

[Lazy JW]

I agree that you don't have much of a problem here. I have one of those guages, just ignore everything except the numbers. It is normal for the vacuum level to drop slightly when a load is added. Remember, the throttle remained at the same degree of opening, so the extra load from the tranny will cause the engine to slow down. Since the engine is now running slower with the same throttle restriction, there will naturally be less vacuum.
Joe

 

[CobraSix]

Those numbers look great. I only get 16inHG at idle right now.

For timing adjustments, you really need to use a timing light. The vacuum gauge will give you an idea, but isn't perfect.

Slade

 

[Anonymous]

20hg at idle is good. If you put it in gear the idle speed will drop down and so will the vacum.

Like everyone else I don't think you have a problem. If it ain't broke don't fix it. To set your timing us a timing light. 12 to 14 degrees BTDC is a good place to start.

 

[Anonymous]

My 200 went from 18 to 21 by advancing it a little. Usually more vaccum equals smother idle and feul economy, so its always good in my opinion to tune the motor for the most possible. As for timing :arrow: I found that the easiest way is to advance the distributor a few degrees, then take it out on the street accelerate hard if it doesn't ping andvance it more if it does retard it a bit and retest it.