Everybody should check their ignition timing!!!

Started by ScottRT, March 21, 2009, 09:12:08 PM

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One thing every mini owner with classic Lucas points-type distributors should check is their distributors advance. I don't feel enough people understand just how important this is for power and economy. So... about that dizzy:

Does it work? Where is it at idle? Does it advance to 32 ~ 33 degrees Before TDC when "all in"?

Lotsa owners probably say "my car runs fine", but these dizzy's do get old and the springs get weak, and you should check it out.

Why should I check?: Having spark timing that lags (is retarded)from what the engine wants can easily cost you 25% in power and economy, yet still appear to run smoothly. Retarded timing also makes and engine start harder and run hotter.

How do I check it?:

-- You need a timing light and a tach, preferably. But first things first.
-- Warm up your engine, and set your idle for 900 rpm. These cars will idle at lower speeds if the carbs are in good shape, but the water pump is very inefficient at lower rpms, and your ignition light will probably be on, so set idle at 900 to 1000 rpm.
-- Disconnect the vacuum advance tubing from the dizzy and plug the end of it during testing. When done, don't forget to hook the vacuum line back up. All street cars can benefit from vacuum advance. More economy will be realised when cruising.
-- Check the timing. Typically somewhere about 10 degrees before TDC is what you should find at idle. Slowly rev the motor up until your get maximum advance, or "all in". Did it make it to 33 degrees, or close to it? At what rpm did things reach 'all in"? Warmed up 1275 and big bore engines generally like all the advance in before 4000 rpm. Smaller bore engines like the timing to advance a little slower to avoid ping...maybe "all in" at 5000 rpm.

If you're not geting results like outlined above, you should have things checked out. A common problem is that the 2 small distributor advance springs get weak, and allow a good portion of the mechanical advance to come in while still only at idle speed. So what happens is people set the idle advance to 10 degrees BTDC, and wonder why they only have 22 or 25 degrees when"all in", and why the dizzy achieves "all in" at only 2400rpm.

It's important for a stable idle that no advance comes in until speeds above idle.

I went thru a few springs until I found a pair that allowed my advance to begin at just above 1000 rpm, and went "all in" at 3750 rpm. My 25D Dizzy has 12 degrees of mechanical distributor advance (24 crankshaft degrees), so I set my idle timing at 10 degrees, and have 34 degrees when I'm all in. SO far the engine loves if, but if it wants to ping during hot weather, I will retard it a couple degrees at a time till it's happy again.

A properly timed engine will happily rev-up. If your engine seems to run out of breath at 4000 rpm it could very well be the timing that's holding it back!!

A word of caution.. Try to find the proper specs for your engines timing requirements. If you have a custom motor, check the popular tuner books for advice on what to try for timing figures. Each engine type has its own perfect advance curve, and different dizzys have different amounts of advance that they throw in. I am merely trying to give enough insight that you can take a quick look to see if your engine is in the ballpark. I know there are ALOT of owners that don't know if they are or not. This is free HP and MPG to be had.

Scott T.


Very nice write up, this is what I like to see!


Copied and pasted for referance. Thank you for such a well written piece.


Not bad advice as I was one of the "it runs fine" guys. Since a PO put the flywheel on wrong I didn't have timing marks anywhere to go by so I procrastinated for a year or two. I finally got a hold of Doug Lawson and he worked me through finding TDC using a dial indicator, making a pointer and marking my vibration dampener for TDC, -5, -10 and -15 deg. It's amazing when you find out you had 38 deg advance on your engine without the vacuum advance engaged. (yes it will run like that) I've worked it down to 18 deg adv and there's much more power and lower operating temps in the summer. I've still got to lower it down to spec but there's other priorities to work on for now. 

So check it when you buy it...   dan


I use to just turn the dizzy till it "ran fine".  It is amazing how much better the engine will run when its done properly. 


I took today off and am going to check mine now


Great write-up and thanks. It does beg the question of where you go to get a selection of springs to get the results needed.


Checked mine yesterday.  Here is what I got:

10 deg @ 900-1000 RPM

29 deg @ 4000 RPM

32 deg @ 5000 RPM

I had a mis-fire problem under heavy load.. 4th gear - foot to the floor.. It was farting & puking at about 4K rpm..
Turned out to be the coil... There was a crack where the wire plugs in.. hidden under the rubber boot.  Changed out with a 3 ohm flame thrower.. now she pulls like a train again.. :)


This would be better if you started out assuming the reader knows squat.

Pretend I've never done this job and give me more details. Particularly what I'm looking for.

Where should the white lines line up? Top point on the jagged edged part/Bottom? What do the jagged edges represent? 1 degree or 10.

John Gervais

I used set my ignition timing by increasing the engine rpm to 2000 and advancing the ignition until the rpms stopped rising, then retarding the ignition until the rpms drop by 250 rpm and clamping the dizzy then returning the idle speed to 1000.  It worked fine, for the most part.

But - now that I've got gauges, I use a vacuum gauge (either the one in the car or under the bonnet and holding a hand-held one) and a downloaded .jpg image scanned from a 1960's vacuum gauge instruction sheet... 

In my opinion, the vacuum gauge is super valuable and frequently overlooked.

Here are the relevant pages:

Hmmm, size matters...

Ok, the nuts and bolts of using the vacuum gauge:

Setting Ignition Timing by using a Vacuum Gauge

1.   Warm engine to normal operating temperature
2.   Leave the vacuum advance unit (if fitted) connected
3.   Ensure that the idle speed is fast enough so that the ignition warning lamp is 'off' - adjust if necessary - 1000 rpm is usually sufficient.
4.   Connect a vacuum gauge to the intake manifold vacuum take-off; many carb spacers have one, if you don't have one on yours, it's nice to have. 
5.   Note the vacuum reading.
6.   RICHEN the air/fuel mixture slightly - the previously noted vacuum reading should drop slightly and remain steady.  This eliminates erratic vacuum gauge readings due to lean misfire.
7.   Loosen the dizzy clamp and if you've got a 25D4 distributor, adjust the vernier wheel to a central position.
8.   Retard the ignition by turning the distributor counter- clockwise slowly and watch the vacuum gauge needle drop slightly.
9.   Advance the ignition timing by slowly turning the distributor body clockwise until the highest vacuum gauge reading is achieved and the vacuum gauge needle begins to 'flicker' or 'kick'.
10.   Retard the ignition timing slightly to achieve the highest STEADY/STABLE vacuum gauge reading.
11.   Retard the ignition timing further, just enough to drop the vacuum gauge reading an additional 3/4" Hg.
12.   Tighten the distributor clamp.
13.   Re-adjust the carburettor idle speed.
14.   Re-adjust the air/fuel mixture.

That's it -

- Pave the Bay -


what if I don't have a tach?  How do I go about doing this project without one?
"In like a lamb, Out like a lion."


Quote from: Dmulder on September 19, 2015, 12:17:33 PM
what if I don't have a tach?  How do I go about doing this project without one?

I had an old junk tach in my pile of parts.  I bet you could get a cheap one at an auto parts store as well. 


Advanced Auto parts and Autozone both seem to carry some basic tachometers under $50.  I would recommend getting an 8000 rpm tach - that will give it some margin at the top as a basic road car can rev very near 6000 rpm.


I've noticed that my throttle response is a bit hit or miss.  Last night i re-checked my timing, it was a bit off so i got it back to 8 BTDC.  One question I had is how stable should that mark be?  It would jump ahead (down a few notches) every second or so.  I would say it was stable for about 80% of the time.  Another thing i noticed is that vacuume advanced was way to sensitive and with very little throttle it would go full advance to 30'ish BTDC.  So that probably needs replacing.  Are these 2 issue or just one?


I dunno.   My car has done the same thing.  I wasn't sure if the occasional timing light bounce was just a function of low tech equipment.   But perhaps someone more knowledgeable will comment?
1988 Austin Mini
2002 MINI Cooper S
1992 Toyota LiteAce (JDM)
1997 Jeep Wrangler Sahara

Jimini II

Slack in the timing chain ? Worn springs in the distributor ?


Although this is now a 9 year thread that I just stumbled upon, it remains a great source of information and is still valid. Two things I'd like add:

If you are running points in your distributor, you should always set your point gap (dwell) to the correct spec prior to checking or adjusting the timing.

To address an unanswered question from above about sourcing advance springs, you can probably get those from Jeff at Advanced Distributors.


I'm still confused. The original poster recommended 10° BTDC @ idle and 32° to 33° BTDC max. Haynes lists 12 different settings from 3° BTDC to 19° BTDC for stock engines at RPMs ranging from 600 RPM to 1500 RPM depending on the model and year, with no maximum given.

My electronic 1-2-3 distributor has tons of dial-in profiles and was originally set by my engine builder. I have no reason to think it's out of spec., but with 10K miles approaching I'd like to check. Short of calling my builder and hoping he still has my build on file, what am I to do?
...the sled, not the flower


You're ok, anything up to 34* total advance is good. 8* is a good starting place.....if it pings back it off a tiny bit.
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad


It is nice for most to have the full correct factory procedure.

But, although I own a timing light, and occasionally use it to see what I've set my timing at, correct timing for any engine depends mainly on the octane of the gasoline and the altitude.

I set my timing to where it has the smoothest/fastest idle, retard it a touch, and drive it. If it pings, I stop and retard it a touch, then repeat until there is no ping.

I set up my Corvair in my shop (after rebuild), perfectly timed for 6200 ft above sea level, and drove home. The next morning, starting towards town from my home at 5600 ft, it pinged a touch, so I retarded it a bit more. When I later took it to my other home at 1200 ft, I retarded it more. The only gasoline sold in town is 80 octane.

When driving a non-computerized car, I usually end up stopping to adjust the timing once or twice on a trip from 400 ft to 6000 ft, or from 6000 to 12,000, which are common drives for me.

The old Land Rovers were great for this, since they had a thumb-screw on the side of the distributor.


Yeah definitely depends on altitude and fuel.  One of the perks to this CB Blackbox ignition system I use on my VW and mini is it's ability to increase timing with altitude.  I can drive around here at 600 feet and have X timing for my max and when I do mountain trips in the summer to as high as 11k feet, it will advance as much as 5 degrees across the board.  It's fully programmable so I can set it to whatever my car likes.  It's just nice not having to make a pit stop in Denver on my way up to the rockies and pull over with a timing gun to set it for the altitude.