Setting Ignition timing a M20B20 or M20B23 - need help

[OLD MAN]

Looking for the best way to set timing on an M20B23 with distributor.

Do you use the cast post on the timing belt cover and cut in crank pulley? Does not seem ever accurate.

[Tom D]

adjustable timing lite.....

[autox320]

Looking for the best way to set timing on an M20B23 with distributor.

Do you use the cast post on the timing belt cover and cut in crank pulley? Does not seem ever accurate.

As Tom suggests using an adjustable light is where it's at. If you can make reliable marks on the front pulley life is much simpler. If can't find any make your own with a bright paint pen when dead nuts TDC.


I'm using INNOVA(model 3568), and very happy with it. Don't be intimidated by the buttons , using this light is as easy as turning the distributor.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

[mxl556]

Hi Daryl, how are you?

To answer your question- yes, mark on the timing cover and a notch on the flywheel pulley, just like on the M10, do not use TDC mark on the flywheel pulley, use the one before it. If you have the timing light that has advance function built in and set the advance on the light, then you can set TDC to the mark on the flywheel cover (i never found these advance function timing lights being accurate). As far as specs go, the trick is to find specific info based on the distributor used (at what RPM how many degrees BTDC). If you have modified engine/cam or anything else it won't be right. If you have the distributor that does not match the mark on the flywheel pulley (# of degrees BTDC) then it won't be accurate.

From my experience setting the timing with the timing light on euro motors is a waste of time due to the fact that they were designed to run on leaded higher octane gas and things were different in general. Back when I had 323i's I always set timing by ear and it was back when 92 octane without ethanol was available in CA. Setting the timing to spec. using the timing light always resulted in pre-ignition, so I always had success doing it by ear.

Hope it helps,
Max

[Tom D]

an adjustable timing light does so much more then just setting the factory specs.

when i was in my teens and just getting into engine performance i would do like Max and tune by ear. at the time i was into drag racing and so my settings were based on open throttle, full load acceleration. to accomplish this you start with the factory setting and then do some power acceleration runs and listen for pinging. if there's no pinging then you advance the timing by 2 degrees, still no pinging advance it 2 more degrees. continue doing this until you hear the ping and then back off the advance by 2 degrees.

this method works well, but has some limits like not being able to repeat the setting, not knowing exactly what 2ºs is and not knowing how much advance you actually end up with, unless of course you're using a degree wheel.

in my mid twenties i got serious and bought a snap-on adjustable lamp and never had to guess again, but there's more. an adjustable lamp will let you check vacuum and mechanical advance, when it starts, stops and how much total advance it adds. furthermore you can check how quickly the advance ramps up and at what rpm. knowing the advance ramp facilitates customization of that ramp for different compression ratios as well as octanes and fuels. it also affords you the ability to quickly and accurately repeat a previous setting or to do fractional degree tuning.

the beauty of this tool is that you can use any known crank mark or by making your own mark with the crank in the T.D.C. position. when i bought the snap-on 40 years ago it probably cost close to $200, but because modern cars don't need to have the timing adjusted and because the mechanics that did use lights are now retiring you can find these lamps for sale for tens of dollars at places like ebay.

[autox320]

an adjustable timing light does so much more then just setting the factory specs.

when i was in my teens and just getting into engine performance i would do like Max and tune by ear. at the time i was into drag racing and so my settings were based on open throttle, full load acceleration. to accomplish this you start with the factory setting and then do some power acceleration runs and listen for pinging. if there's no pinging then you advance the timing by 2 degrees, still no pinging advance it 2 more degrees. continue doing this until you hear the ping and then back off the advance by 2 degrees.

this method works well, but has some limits like not being able to repeat the setting, not knowing exactly what 2ºs is and not knowing how much advance you actually end up with, unless of course you're using a degree wheel.

in my mid twenties i got serious and bought a snap-on adjustable lamp and never had to guess again, but there's more. an adjustable lamp will let you check vacuum and mechanical advance, when it starts, stops and how much total advance it adds. furthermore you can check how quickly the advance ramps up and at what rpm. knowing the advance ramp facilitates customization of that ramp for different compression ratios as well as octanes and fuels. it also affords you the ability to quickly and accurately repeat a previous setting or to do fractional degree tuning.

the beauty of this tool is that you can use any known crank mark or by making your own mark with the crank in the T.D.C. position. when i bought the snap-on 40 years ago it probably cost close to $200, but because modern cars don't need to have the timing adjusted and because the mechanics that did use lights are now retiring you can find these lamps for sale for tens of dollars at places like ebay.

Bang on Tom. Until this build I too have always just done by ear and WOT pulls. The light does let you see whats going on. Idle setting, but also when hold throttle can literally see the advance using pulley mark as reference. I've never had a light for advance well cause many these days don't even mess with distributors anymore. Yup can see the curve of if the springs are light enough etc can use the light and KNOW what advance you've got total and what rpm it's full IN.

Even with high octane I'd be cautious with way too much advance. Could have a lot of timing and never hear detonation/ping. It will work for awhile Can and will kill rod bearings. Signature horizontal (crank line) hammer lines in the bearing surfaces. This is common with guys going overboard on S14's timing. About the same for any motor.

[Somjuan]

I'll have to prove that for you! I've had mine set to about 30* at 2200 for the last two years unless it's actively being smogged, once the engine gets pulled I'll take the bearings out for kicks and giggles. I bet you're right, the oil pressure light has been taking a bit longer to get going lately.

Also let me serve as a precautionary tale here - buy a good timing light. Mine was off by seven degrees somehow? Still haven't figured that out.

[OLD MAN]

I understand the whole adjustable timing light thing been using one for years.

Need to know more about where to point it - the Alt is in the way on my track car engine to get a good line of sight on the front pulley and post on the timing belt cover.

I have always set my M20B20 and now the M20B25 (using the B20 disy) at 32 degrees total advance at 2,500. I can not use the vac advance do to the carb I am running and the disy only has 12 degrees of mechanical advance in it. What I need to do is find $$$ and go to electronic crank fire for this poppy!

The timing post on the timing belt cover has a blunt end on it that is more then 1/8" in diameter - fat and not pointy.

Thanks for all the help will use it for sure.

M10s are so much easier to adjust with the hole in the tranny and marks on the flywheel. The tranny I have in the track car does not have a hole in the tranny bell housing.

- - - Updated - - -

an adjustable timing light does so much more then just setting the factory specs.

when i was in my teens and just getting into engine performance i would do like Max and tune by ear. at the time i was into drag racing and so my settings were based on open throttle, full load acceleration. to accomplish this you start with the factory setting and then do some power acceleration runs and listen for pinging. if there's no pinging then you advance the timing by 2 degrees, still no pinging advance it 2 more degrees. continue doing this until you hear the ping and then back off the advance by 2 degrees.

this method works well, but has some limits like not being able to repeat the setting, not knowing exactly what 2ºs is and not knowing how much advance you actually end up with, unless of course you're using a degree wheel.

in my mid twenties i got serious and bought a snap-on adjustable lamp and never had to guess again, but there's more. an adjustable lamp will let you check vacuum and mechanical advance, when it starts, stops and how much total advance it adds. furthermore you can check how quickly the advance ramps up and at what rpm. knowing the advance ramp facilitates customization of that ramp for different compression ratios as well as octanes and fuels. it also affords you the ability to quickly and accurately repeat a previous setting or to do fractional degree tuning.

the beauty of this tool is that you can use any known crank mark or by making your own mark with the crank in the T.D.C. position. when i bought the snap-on 40 years ago it probably cost close to $200, but because modern cars don't need to have the timing adjusted and because the mechanics that did use lights are now retiring you can find these lamps for sale for tens of dollars at places like ebay.

Marking TDC on the crank pulley needs to be done with dial indicator and head off correct? I have seen those tools that screw into the spark plug holes and measure out with compression - are they ever accurate?

[Tom D]

I understand the whole adjustable timing light thing been using one for years.

my post above wasn't meant for you old man, i expected you would know this, but rather directed to the others that don't.

if i was you i would just make my own marks in a location that is easily accessible using a dial indicator and a paint pen.

does the M20 have a TDC locater hole/pin insert like the M42, i forget.

[autox320]

I understand the whole adjustable timing light thing been using one for years.

Need to know more about where to point it - the Alt is in the way on my track car engine to get a good line of sight on the front pulley and post on the timing belt cover.

I have always set my M20B20 and now the M20B25 (using the B20 disy) at 32 degrees total advance at 2,500. I can not use the vac advance do to the carb I am running and the disy only has 12 degrees of mechanical advance in it. What I need to do is find $$$ and go to electronic crank fire for this poppy!

The timing post on the timing belt cover has a blunt end on it that is more then 1/8" in diameter - fat and not pointy.

Thanks for all the help will use it for sure.

M10s are so much easier to adjust with the hole in the tranny and marks on the flywheel. The tranny I have in the track car does not have a hole in the tranny bell housing.

- - - Updated - - -




Marking TDC on the crank pulley needs to be done with dial indicator and head off correct? I have seen those tools that screw into the spark plug holes and measure out with compression - are they ever accurate?

If can't find any other method could use poor mans TDC finder. An old spark plug with the center knocked out; weld in a bolt to make a locator. Can use in cyl one with a degree wheel and split the difference to find true tdc.

Yeah the M42/M5x motors having the starter lock pin in the flywheel to lock the crank at TDC is handy sometimes. Usually this is why when engine out I try to make sure of marks and make a new bright line up at TDC to read to tune. In that M20 case I'd just make my own pointer so can use the light.

[OLD MAN]

Sorry Tom D - was late last night and too tried to reply, but did. All good.

I will have to make some easier to see points for timing.

- - - Updated - - -

Hi Max - I am doing good keeping busy fixing things around the house before and after the knee replacement surgery.
need to get out there and find a job now being home 24-7 is not for me!

[320iAman]

Hi Daryl. How are you and yours ? Well I trust. I never ever used a timing light on points, I always used a dwell meter, without a slide door on the distributor cap and adjust dwell with the motor running, one has to set the dwell ,check it, stop the motor adjust the points again and recheck the dwell or use a remote starter and insert feeler gauges until your at the dwell best for your cam, plug gap and points. Use a good dwell meter and don't look back,,lol,, Using dwell your looking for the longest time and highest amount of spark you can achieve- max power-too much or too little dwell yields weak spark.

Of Course there is the oldest method, set it by ear, test it and redo as necessary.

Randy

[320iAman]

There is also switch to electronic ignition where setting dwell is not really an issue as the transistors do the switching for the points and do it so fast that setting dwell is not in the equation. The real trick is finding a High Output Coil,Plug Lines and Plugs for this setup, oversize wires to coil primary input/output wires is standard to combat voltage drop plus using a larger output Alternator should not be overlooked, I have noticed that dropping the 65 A alternator and using the 80A or 100A alternator stabilizes Higher Coil out better on the Coil to Dizzy Line. The point I'm making is higher spark in the combustion chamber burns more more fuel less CO ect thus more power.. The higher voltage further reduces heat which increases amperage flow and speed, the 2nd part of Gerog Ohms law most dont utilize.

In 12 DC Volt Car systems a few points of voltage is significant with 120 AC its not really as big an issue. Your Fuel Pump Relay could us an upgrade as well, the back story,,Besides mine dying in a year or so, I noticed it was cutting out at higher speed, I changed out the NE555 timer that BMW KAE uses to Mil Spec SE555 timer which is a like Child to Adult Strength and issue resolved.. Send me one of yours and I'll install it,,lol Plus I did a Hella upgrade which helped as well.

The Coil output example 20KV Coil Line to Dizzy to 5KV Dizzy to Spark Plug is a 4 to 1 drop squeezing this ratio down some will have benefits,,increasing the denominator, the divisor ..

Randy

[OLD MAN]

We are doing great Randy thanks for asking. You doing well?

Thanks for all the help.