engine TIMING and advance curves

[mk1mini]

Hi all ,

Recently with the help from forum members I have improved the timing of my 1380cc engine.
Throughout my learning process I have been looking into the timing process for a modified "a series" taking in to account the advance curves from standard and "special" curved to the engine distributers.

Smiffy from the forum advised me to set the static timing at 16degrees to which I road tested and the result was a huge improvement to my initial 10/12 degrees I have always ran with. I have read that the maximum advance for an "A series" @ 3500 - 3700rpm is 34 - 35 degrees. I then checked what my maximum advance was using a strobe and creating a 30 and 40 degree mark on the bottom pulley. The answer read = 35 degrees maximum advance. I then wanted to find out the mechanical advance the distributor gives using this calculation;

35{total advance} - 16{static advance @1000rpm} = 19 {total mechanical advance}

I have understood things so far after taking the time to read articles and try/testing techniques. My question is ... Is this a coincidence my 59D4 distributor is at perfect maximum advance making and making a good curve ?

If it was under the maximum advance I take it that is when you would modify the "stops" for the advance to gain more advance ? and if it was over the maximum advance {dangerous} that is when you would add material for less advance travel ?

have I hit the nail on the head or made a huge error in understanding the curve ?

Many thanks , hope this thread could possible help others understand the curve and how to find figures.

mk1mini

[Earwax]

Hi mk1 mini

lots of different views on timing.

just as you proposed the perfect curve is 16 + 19 = many would say 10-12 plus 20 = 32 is pretty good ( which A) is pretty close to standard set ups for modded engines and B) is probably pretty close to what the 59 dizzy was specced to.

Now i have heard of people setting static timing at 16 in race engines , it certainly stops run on, but i personally think 34-35 degrees total is too advanced. Again my experience for guys using avgas RON 100plus, is 31-33 tops . however the perfect tune, timing set up for your engine is pretty unique and only worked out precisely by lots of fooling around on the dyno changing curves...

[Spider]

Yes, that is the basics of the total distributor advance and any initial setting.

Note that when a static figure is referred to it means that the engine has stopped, not running, ie, it is static

Some caution is needed when setting the dissy to a static setting as there is always free play (slop, wear, call it what you will) between the crankshaft and the points, there are a lot of parts in between.

What also needs to be taken in to account with advance curves is the rate of advance. have a look at some of the graphs I've posted up in the forum in recent days.

If you are considering modifying a dissy to give it more advance, that's fairly easy, just file a little bit of the stops on the of the cam plate. If you want to reduce the amount of advance the dissy will have, it can get a little tricky as the parts are rather small. It is possible and easy to slip a sleave (small tube) over one of the stop posts on the shaft, however they do need to be on the heard side as they do get a bit of a pounding. The better way is to TIG a bit of metal on to the stops on the cam plate and file them back.

[Smiffy]

A bit like ian with his vacuum advance, I never mentioned static timing either:

Theres not enough timing, set it to 16 degrees at 1200rpms. But when you drive it listen out for any sign of pinking and don't give it full throttle under load just yet.
The other thing I say looking at the pic's, is check and adjust your valve clearances.

[rich@minispares.com]

. I then wanted to find out the mechanical advance the distributor gives using this calculation;

if you look at the advance weight in your dizzy it will have a number stamped on it.

double this number (which is the mechanical advance), minus it from your required/expected total advance and you will have a number for your static timing figure

i.e

10 stamped on weights = 20 minus total (say 28) = 8 degrees static - this method works a treat

[mk1mini]

if you look at the advance weight in your dizzy it will have a number stamped on it.
double this number (which is the mechanical advance), minus it from your required/expected total advance and you will have a number for your static timing figure
i.e
10 stamped on weights = 20 minus total (say 28) = 8 degrees static - this method works a treat

Just checked this out ! the weight has a 9. stamped on it ,

9+9=18 {weight} 35deg{total advance} 35-18=17degrees {static advance}

I wasn't far away at my 16 degrees !!!!

nice one rich , that's a great bit of info for everyone

[mk1mini]

A bit like ian with his vacuum advance, I never mentioned static timing either:

Theres not enough timing, set it to 16 degrees at 1200rpms. But when you drive it listen out for any sign of pinking and don't give it full throttle under load just yet.
The other thing I say looking at the pic's, is check and adjust your valve clearances.

when I did the above and returned it to idle it was pretty much 16.
Thanks for the help smiffy

[rich@minispares.com]

17 degrees static will be a git to start though

I would be keeping my eye out for a set of 13 deg weights to try and give a more reasonable static figure of 9.


I had a set of 13's in a really high comp 1293 years ago, it started on the button, stopped on the button and never, ever pinked - this was in the days when getting expensive dizzys or getting the curves mapped was just an unknown to us youths

[ianh1968]

My question is ... Is this a coincidence my 59D4 distributor is at perfect maximum advance
making and making a good curve ?

Answer: Yes

ANY distributor can be set to produce 35 degrees maximum advance,
just by swinging it round as appropriate. If the lower end of the scale
ends up somewhere close, then this was entirely LUCK if this was not
using a custom curve worked out using a dyno. In this instance, the
timing was set at the lower end of the scale, and by LUCK, worked out
at 35 degrees, max.

There is still the SHAPE of the curve between the two points checked
that needs to be considered. The could still be completely wrong and
costing power and/or economy...

There is a range of maximum total advance figures that the 'A' Series
has used, from about 28 degrees maximum up to 34 degrees, or
thereabouts. The RPM at which these figures are achieved can vary as well.

Some distributors "top out" at 3000, others do not. Some figures that I have
found for an Aldon Yellow show 36 degrees, and this being with the curve
advancing all the way up to 5000 RPM, far higher than the 3500-3700 RPM
being suggested here.

On my last dyno session I started off with 32 degrees, then 34, then 36:
All showed an improvement. When I went to 37 degrees, the power curve
went wobbly, so it was backed off to 36 degrees. My maximum advance
was programmed at 5000 RPM, the same as "Yellow".

For the record, the increase of 4 degrees advance from 32 degrees to
36 degrees produced an increase of 6BHP at the wheels. Obviously, in the
midrange the difference was not as much, but was still significant.

Given that most road-driving is done in the midrange, this element of the
timing should not be neglected. Almost always, better results are obtained
by using a dyno.

In the "Old Days" they used to reckon that going from a standard
small-bore head to a 12G295 head was worth about 6BHP. So it figures that
going to a dyno can realise as much extra power as fitting a decent head,
probably at far less cost... How much would you pay for a decent head?

You possibly have extra power available to you, especially in the midrange.
You may not be able to access this unless you have the advance curve that
your engine is crying out for.


Ian

[Smiffy]

LOL was nothing to do with luck ian it's called experience

[mk1mini]

LOL was nothing to do with luck ian it's called experience

it was pretty much smiffys suggested 16 that has tested fine and the figures work out ! cheers lol

[ianh1968]

This. Is. Amazing...

Knowing only the engine size, the carb, and the "body style" of the distributor,
isn't it absolutely incredible that one can deduce that the existing "unknown"
curve in the present distributor might work "OK"? ...

No, this is not "luck",
No, not even "experience"...
This is total and utter genius! (Sir)

This section of the forum is called "Technical Talk", the hint is in the name...
Much very relevant "technical" information been offered in threads recently
by some parties, and absolutely none at all by others.

There has been a good deal of discussion on the subject of the actual shape of the
advance curve required by the engine. Variations in the rate of change, steps, and
other external features that are very pertinent to this subject.

Sadly, much of this information appears to have been completely disregarded,
for reasons that I cannot work out. You can lead the horse to water, but you can't
make it drink...

However, everyone is happy:
mk1mini, you are happy because your engine works "better" than it did before.
How well it could work, is another matter and one which you may never find
the answer to... You have been "Blinded by the light"!

Smiffy, you are happy because you have another satisfied "customer"...

Me, I am happy because as a result of what has been discussed here,
I managed to work out my "pinking" dilemma...

Hopefully someone at some point will read some of what has been posted recently
and will have a "Eureka!" moment of some description as a result of it.

Sincere wishes to all.

Ian

[mk1mini]

However, everyone is happy:
mk1mini, you are happy because your engine works "better" than it did before.
How well it could work, is another matter and one which you may never find
the answer to... You have been "Blinded by the light"!

Ian

?/?

I have not been blinded by any light , you assume I am just going on what smiffy says as gospel , I have worked out the figures and it all seems an accurate calibration. I understand you think it can be better etc. but to be honest I personally like to understand the process and do it myself rather than hand it over to a dyno operator to say "yes its too advanced" and that's it .
I know a dyno is accurate , I know every engine set up is differently and requires unique timing figures.

If it was up to you I would have been £100sss into aldon distributers {not guaranteed to be bang on with my set up either I might add} as they yellow and red are off the shelf. £100s in back in forth to the dyno which is hundreds of miles away.

All I wanted to do was get a more accurate timing setting for my 46 year old road going car. I personally think through everyone's help and input I have succeeded. And I understand the process despite your patronising "blinded by the light" remark.

Maybe one day I will get it dyno'd but I am happy with the running for what I need and my usage of the car.

Buying tarty parts isn't the answer I wanted , Understanding the parts I have and how they work and are set up is the answer I wanted .

[Smiffy]

LMFAO, You'd have learn't a lot more if you'd just asked questions, personally I think we've had a influx of members from That other Min Forum.
Which has only ruined what was once a forum free of all the bull shit that happens over there.

[mk1mini]

LMFAO, You'd have learn't a lot more if you'd just asked questions, personally I think we've had a influx of members from That other Min Forum.
Which has only ruined what was once a forum free of all the bull shit that happens over there.

Thanks anyway for the help smiffy, i appreciate your experience.