Vacuum Tuning & Recently Advanced Vacuum Advance Fallacies

[Budgie]

Just want to say a big Thankyou to all who take the time to educate people like myself. I normally brake things and have the sumpies and framies fix em .
I have some time off at the moment to work on my jeep, and based on the info provided in these forums, tuned the old girl today using a VG. made some minor adjustments and she sounds great and runs better. Thankyou for giving numpties like myself the information and confidence to give things a go.

Regards
Budgie

[Mike Wright]

Just wanted to bubble up this thread. The 1st page is the best. Most, but not all, of the rest of the pages are naysayers, grumblers, etc.
Thanks John and a few others

[Michael Browne]

Why is everybody with a different opinion declared a naysayer and sceptic???

Let me say for starters, I have always used a timing light. Why is it so hard to use it? You just point the thing down there and get the mark on the flywheel.
Said that, listening to John time after time about a vacuum gauge got me intrigued. I bought one and tested my jeep and it scored steady needle in the green. Now I know my jeep is tuned perfectly, and it makes me feel great that I'm doing good mechanic skills, backed up by the VG.

What this tells me is Dino was quite capable of correctly tuning a jeep without the vacuum gauge.

More than a few years ago when I was a green apprentice I asked a brilliant mechanic why he didn't hook up the Vane tuneup machine to a car we were working on ... his answer ... " why waste time hooking it up to only have it tell you you need to adjust tappets, clean plugs, set point gap and dwell etc etc "
So we went through all the things we knew needed to be done for a correct and successful tune .... and THEN hooked up the Vane to double check our work and see if plug leads and coil were ok.
I see a vacuum gauge as ONE of the tools used to detect problems but mostly I use my eyes, ears and fingers to find the scource of a problem. I don't need a VG to tell me the pop pop in the jeep exhaust at idle is a sticky valve, my ears tell me that, and a couple of years experience.

I have at least 4 vacuum gauges in my shop set up for different jobs but they are not my first point or reference.
Each and every engine type behaves differently with the VG ... and what do you do with it on a diesel engine

Cheers

[Mike Wright]

Hi Mike,
Thanks for your comment. I'm NOT slamming folks who use other methods like Dino, (Who I know and respect) Just folks who believe theirs is the only way and say negative things. Remember, most of us are not professional mechanics, like me, and I use any and all tricks, and advice I think is good. For me, a vacume gauge helped me to tune my GPW to get the max effectiveness out of the motor. Like I stated earlier on page 1 or 2 I can now pull a hill here in Leavenworth in 3rd gear that before I had to downshift.
Mike

[Seff]

How lovely to have been quoted in the original post, without any word of warning, or indeed a chance to defend my points.

First of all, I use a vacuum gauge to diagnose and to tune my various carburetors. It's a tool with many uses - but my original statement stands; it's not good for setting timing. I don't know if I'm being lumped in with the "decriers" and "naysayers" because of this, but I hope not.

I feel that I have explained my statement several times, to no avail. No evidence other than "that's how I do it" to counter my points. I don't know what to do. Is anybody interested in my reasons for contesting the claims put forth in this thread? It doesn't feel like anyone is really interested in determining what is right and wrong, as much as they seem to be cheering for their own team. No offense.

[Michael Browne]

Using the VG is a fine way to tune your engine but adding a simple tutorial for owners of some of those 200,000 jeeps produced BEFORE a vacuum port was introduced on the intake manifold would be equally valuable.

Chuck,

It is quite simple really ..... leave the vacuum gauge on the tool board and hook up your tachometer and use it and a timing light and dwell meter to tune the engine.

Funny thing with the vacuum gauge is it is only one of the possible tools that can be used to obtain good engine tune.

Look at the gasoline powered engine as a vacuum pump (and a compressor for that matter) and the highest possible engine speed obtained with the throttle plate closed in the idle position is also the best possible manifold vacuum you can achieve. Vacuum is achieved because the carburetor throttle plate is closed restricting the air entry to the engine and the pistons on the intake stroke are pumping out the air and raising the manifold vacuum.

Using a timing light will allow you set the initial timing at 5 deg advance making sure the mechanical advance weights haven't begun to change the timing prematurely. This can be easily checked by increasing the rpm and observing the advancing of the timing marks. If the timing increases too soon or doesn't change at all then the weight mechanism needs to be fixed.

Then using the tachometer you can rotate the jeep distributor clockwise until the highest rpm is made and then retard the timing (counterclockwise) by a small amount to prevent too much advance causing pinging under load and also hard starting. How much you have to retard the timing (CCW) will depend on your fuel type, engine condition, altitude and atmospheric pressure. Road testing is recommended and once you have established a feel for this method you can very competently tune your jeep. It should be noted that very little improvement in overall engine performance can be gained by having the timing set too far from the factory setting of 5 deg advance.

So no need to drill any vacuum ports, just trust your other tuning equipment.

Cheers

[artificer]

One thing one must keep in mind is that the vacuum pump/compressor [engine] should be in good mechanical running condition otherwise one is just wasting their time trying to tune all the other 'bits'.

The first port of call vacuum gauge is used for all the prelims, diagnosing & pin-pointing any abnormality causing low or indicated incorrect manifold vacuum reading/s, before ever trying to do a 'tune-up'.

Diagnosis using this great inexpensive, time saving tool helps all, before spending beaucoup bucks guessing, then replacing unnecessary parts one after the other!

How often do we hear this parts replacement & guessing with NO POSITIVE RESULT, on here?

[Michael Browne]

The first port of call vacuum gauge is used for all the prelims, diagnosing & pin-pointing any abnormality causing low or indicated incorrect manifold vacuum reading/s, before ever trying to do a 'tune-up'.

John ...

A vacuum gauge doesn't need to be the first tool / thing you use..... your ears and eyes are first and then make a selection from any number of tools.

And you missed the point of my post.... it was directed jeep owners with earlier jeep engines that don't have a vacuum port so not an option.

So no matter how cheap a Harbour Freight vacuum gauge may be it is of no value bit like a hip pocket in your singlet, nice thought to have but useless in practice

[Chuck Lutz]

Thanks Michael.....1/3rd of all WWII jeeps thank you as well.

[artificer]

Mike Wolford's great suggestion from his bag of tricks FULLY answered Chuck's objection/question way back on page 1.
Something that has been addressed for him previously in numerous threads.
~Any jeep with a PCV valve has a vacuum port~

This thread started as an endeavour to educate folk on the uses of & how to use a vacuum gauge.
This in an effort to avoid what has again evolved into semantics & misinformation, regarding this tool.
It was successful until the usual co-conspirators got into the fray. Now it is 5 or maybe 6 pages of primarily BS & conjecture.

The vacuum gauge is a simple tool used by mechanics in an era before scopes, OBD's [on board diagnostics], computers, etc. & modern innovations meant to help with DIAGNOSIS/SETTING.
The vacuum gauge still works as well now, as it did then, on these old engines, before any of these new very expensive introductions.
It is also used regularly on the modern gas/petrol engines in testing & diagnosis.

Most naysayers have something in common!
In general they have a deep seated inability to isolate then fix what is actually wrong, becoming preventative maintenance types, guessers & basically parts changers.
There is no real comprehension of what DIAGNOSIS actually means.
Isolating good & establishing bad or underperforming.

On this thread the usual gang of 4 & occasionally 5 or 6 nay sayers [on other threads] are just P'ing, in one another's pockets in full view.

More often they just email one another, stealing/sharing G members private email addresses. Members who are then unknowingly often bombarded with demeaning, nasty abusive emails from a demented, vitriolic & self banned ex G member, who clearly shows his typical colours early in this thread.

All this conspiring to try & screw up helpful threads, like this one was meant to be.

We could & should all learn from the mistakes over these 5 pages ~~~
Here are some:

Tuning by vacuum gauge is not wise when the jeep does not come with vacuum advance built into the ignition.
So what? Vacuum advance has nothing to do with influencing MANIFOLD VACUUM or using a vacuum gauge.
A vacuum advance line [& there isn't one on WW2 Jeeps], is plugged off when testing.
No one needs a VG to find out their engine is good
The first thing in 'real' diagnosis is establishing what is good & doesn't need attention. A vacuum gauge assists in doing this.
Using a VG to find out why the engine is bad is a complete different story
The gauge serves many purposes if one takes the time to master properly
Remember, most of us are not professional mechanics....
So true & this shows.
Experienced mechanics usually are not guessing but diagnosing & fixing what is wrong.
Not addressing things that are not faulty or not out of adjustment.
....I asked a brilliant mechanic why he didn't hook up the Vane tuneup machine to a car we were working on ... his answer ... " why waste time hooking it up to only have it tell you you need to adjust tappets, clean plugs, set point gap and dwell etc etc "
I remember the time these scopes etc. came in & the naysayers of the day were on about these new gad fangled machines, that BTW tell one nothing about tappets, but this "brilliant mechanic" was most likely doing work that was unnecessary.
Still charge out $ & charging out a full days labour is & always has been what most mechanics are concerned about.

Why do a full tune if there is just a bad plug lead or spark plug?
Something the Vane tester with scope would have told him & how much work is it to hook up one of these machines? 2 or 3 minutes v/s 1.5 to 2 hours doing a most likely unnecessary full tune.

If the vacuum gauge, dwell/tacho readings are all good & the vehicle is performing well, why is a mechanic [or DIY'er] doing anything?
So we went through all the things we knew needed to be done for a correct and successful tune .... and THEN hooked up the Vane to double check our work and see if plug leads and coil were ok.
The very expensive Vane, Sun or whatever tuner scope etc. would have told anyone who could use & interpret, that most of what was done was not needed.
Just the same as a vacuum gauge, dwell/tacho can do & be used for similar purposes by anyone especially to those with a lower skill level & a less bulging wallet e.g. DIY'ers.

[Seff]

Maybe people would argue less if the information you presented wasn't misleading, or even downright incorrect.

[artificer]

What is misleading or incorrect regarding anything I've offered on this topic/thread?
If needed, I will correct myself or elaborate, as I have once or twice before on other topics.

I certainly won't be taking too much notice of unfounded statements as related to:
1. poor comprehension
2. lack of understanding of causes of engine vacuum related issues
3. those who haven't mastered all the uses of this good cheap tool, thus rubbishing the tool
4. total red herrings e.g.

tuning by vacuum gauge is not wise when the jeep does not come with vacuum advance built into the ignition.

So I'll clock off for now with:
No-one has indicated there are not other methods of diagnosis testing & tuning any engine.
I for 1 would be using any combination that suits the circumstances.
It is just that I prefer to test with the gauge before getting in 'there'. Takes just a few minutes to establish where one is.

[dinof]

It sounds like some people here don't know what the gauge is used for......But if you don't like a vacuum gauge then don't use one. Your life will go on don't worry. I guarantee it. I can also guarantee that the vacuum gauge is still a vital gauge that still today serves a purpose.

[Seff]

As I wrote in reply to your PM to me, Artificer, the only misleading part of your thread here is setting timing with a vacuum gauge. I agree entirely that the VG is a good diagnostics tool - and yes, it has many uses. I use it to set my idle mixture on both my carbed vehicles.

I can explain why setting timing with the VG is a bad idea, and I will if anyone's interested. I won't if everyone keeps treating the subject like religion, going "my way is best no matter what the facts are".

Artificer has presented me with an author of engine tuning and maintenance books that he believes supports his claim. I don't have access to his books, so I have asked for more specific documentation.

Dinof:
...Or maybe certain people here understand the values of the VG perfectly well, and also understand its limitations perfectly well. As I said, this isn't a religion; it's a matter of facts. There's no "my team" and "their team", there's only right or wrong.

[artificer]

Getting back on topic & not personal subjective assertions....there are right & wrong statements littering this thread on Vacuum Tuning....

No one can explain why it is a bad idea to use a vacuum gauge for timing, if done properly.
It is not & has been used since the early days of the automobile.
It is particularly good to use in getting a well running Jeep to perform better/optimally.

There are many books & publications if one searches "Ignition Timing Using a Vacuum Gauge" then go to MORE then click on books.
Of course the US Military has it's own TM with instructions on how to do ignition timing & testing using a vacuum gauge. Try this link & save:
http://www.liberatedmanuals.com/TM-9-4910-477-10.pdf