Learning to Tune

[Scallops]

Folks - As you might be aware, I have just got Matilda back complete with a rebuilt engine. This is great, but I need to set a few key parameters on the vehicle before I end up needing another rebuild.....

Firstly, the fuel mix screw on my Solex was taken out when a new kit was put through it. I have the instructions as to how to reset this, but I can't pick when it hunts, one of the steps in setting the mix right.

I also need to reset the timing properly, because last weekend, the condenser blew, and the distributor was messed with thinking it were to blame. I also want to set the points gap correctly then learn how to read the dwell angle to set them that way thereafter.

I have a automotive multimeter which should allow for all of these items to be accurately set....just would appreciate some hands on guidance so it's done properly.

And I want to learn the "bulb method" for timing.....

I am thinking that a combination of too lean/too rich and bad timing is only going to damage my valves, so Matilda is going nowhere until I can resolve these things. I'd just take it to a mechanic and get it right if I could, but no-one will go near a 1956 Land Rover - there again, I'd prefer to be able to do all of this myself.

Might we organise a workshop where we address these items, and even film it for this area's archives?

[Blknight.aus]

more than happy to lay it on for you for your practice runs and then when youve rehearsed it you can do the vids.

[S3ute]

Dan,

Hello again.

If this turns into a workshop opportunity, I would be happy to sneak onto the list.

Cheers,

Neil

[Scallops]

Dan,

Hello again.

If this turns into a workshop opportunity, I would be happy to sneak onto the list.

Cheers,

Neil

You will, Neil.

[Scallops]

Anyone else reckon they can fly an automotive multimeter to calculate dwell angle after we set the points gap with feeler gauges?

And looking at where the rpm is hunting with a auto multimeter once the mix is made richer?

Bulb timing? It would be a great skill for Series drivers to master and several old hands might help to pool knowledge.

Anyone else got anything to offer?

[weeds]

whack a diesel in it Dan

[Scallops]

whack a diesel in it Dan

:D Sacrilege. The 2 litre spreadbore is a masterpiece that gets confused with a tractor engine.....:p

[marting]

Hi Dan
We always used to (and I still do) use a timing light with dwell angle gauge built in. Kills two birds with one stone so to speak!
You really should be able to hear (and feel) the engine revs change as you wind the idle mixture screw in and out. Try winding the screw right in, does it stall? It should!
If it doesn't there is another problem. Problems can include revs too high so the carby is starting to draw fuel out of the main jet, or air/fuel leaks internally, or blocked idle passages.
Cheers, Martin

[Scallops]

Hi Dan
We always used to (and I still do) use a timing light with dwell angle gauge built in. Kills two birds with one stone so to speak!
You really should be able to hear (and feel) the engine revs change as you wind the idle mixture screw in and out. Try winding the screw right in, does it stall? It should!
If it doesn't there is another problem. Problems can include revs too high so the carby is starting to draw fuel out of the main jet, or air/fuel leaks internally, or blocked idle passages.
Cheers, Martin

It does stall, Martin. There is nothing wrong with the carby.....nothing wrong with any of it. I can hear the engine revs change when I adjust it, but doesn't hunt mean go up and down? I can't pick that - just up - or down.

[marting]

Hi Dan
The engine doesn't need to hunt as such. What you are really looking for is the sweet spot where the idle is the smoothest (generally also the fastest). Try winding the mixture screw in until you hear the engine revs start to slow and then wind the screw out about 1/3 to 1/2 a turn. This should be close to the correct mixture, and the engine should be happiest here. Check by continuing to wind the screw out, the engine revs should change (slow) again within at most another full turn.
Also this needs to be done with the engine at normal operating temperatures.
Cheers, Martin

[Scallops]

Hi Dan
The engine doesn't need to hunt as such. What you are really looking for is the sweet spot where the idle is the smoothest (generally also the fastest). Try winding the mixture screw in until you hear the engine revs start to slow and then wind the screw out about 1/3 to 1/2 a turn. This should be close to the correct mixture, and the engine should be happiest here. Check by continuing to wind the screw out, the engine revs should change (slow) again within at most another full turn.
Also this needs to be done with the engine at normal operating temperatures.
Cheers, Martin

The above info is just what I was looking for, so rather than just thank the post - I thank you in person. :)

Made some progress tonight, with Killer dropping by to lend assistance. So - firstly set the gap. I turned the engine over with the hand crank, until we hit TDC...my flywheel has been marked for this purpose, so we align the marking with the white triangle indicator seen through the flywheel viewing cover....now we could set the gap using feeler gauges (mine had closed up to 6 thou) so we sorted that to about 15 thou....all you need is a flat end and phillips screwdriver. Gap set. Right, now....attach the 5W bulb to set timing the next task....positive to low tension connector, negative to earth....turn the dissy, and finally the bulb starts a glowin as the points just open - timing set correctly.....so I tightened that darned distributor nut.....so she's all good. Sounded so sweet when we fired her up.

Armed with your info above, Martin, I have no fear and will attempt to set my carby tomorrow night!

My plan is to make an instructional video of the entire procedure for everyone's benefit.....Maybe all of this is common knowledge, but if it helps even a single extra soul, then it'll be worth it.....and we can drink beer! The vid will feature the who's who of Land Rover madness....the good knight, Killer, S3 ute et al - so stay tuned for that extravaganza. :)

SLOW Inc's first feature epic. Will post an official workshop day for those wishing to be extras.

[Scallops]

Would I be right to think that dwell angle will vary with rpm? Maybe decrease with increasing rpm? The reason I ask was because I was going to ask if anyone had measured a 2 litre spread bore dwell angle when the gap was set correctly, but then I pondered that the angle would vary between engines dependant on their actual idle rpm.

Is this right?

PS - doing some further research, I realise it's wrong. The Dwell angle should be the same for any given engine, at any rpm, when the gap is set correctly. Anyone have a figure for the 2 litre spread bore engine? Somewhere around 50 degrees? Or shall I just inform the world tomorrow.....

[marting]

Hi Dan
Thanks, I am glad I could help.
Dwell angle for a 4 cylinder should be 52 degrees regardless of engine type, displacement etc.
The dwell angle represents the degrees of distributor shaft rotation the points are closed. The remaining 38 degrees (360 degrees divided into 4 lobes = 90 degrees 52 + 38 = 90) are taken up with the opening, open and closing action of the points. By setting the timing you are setting the point at which the points open in the ignition cycle, and consequently send spark to the plug.
Setting the points gap sets the dwell angle. You are right; the dwell angle should remain steady. Worn distributor shaft bushes will cause the dwell angle to alter because the shaft will not be running true.
Cheers, Martin

[Scallops]

Hi Dan
Thanks, I am glad I could help.
Dwell angle for a 4 cylinder should be 52 degrees regardless of engine type, displacement etc.
The dwell angle represents the degrees of distributor shaft rotation the points are closed. The remaining 38 degrees (360 degrees divided into 4 lobes = 90 degrees 52 + 38 = 90) are taken up with the opening, open and closing action of the points. By setting the timing you are setting the point at which the points open in the ignition cycle, and consequently send spark to the plug.
Setting the points gap sets the dwell angle. You are right; the dwell angle should remain steady. Worn distributor shaft bushes will cause the dwell angle to alter because the shaft will not be running true.
Cheers, Martin

Wow - that is great information Martin.....so the Dwell angle will be 52 degrees for any 4 cylinder engine? I'm interested to hear that because it had been suggested that I set my gap with feelers, then measure the angle, write it down, and from then on set my gap using my multimeter, guided by the angle deduced as just put.....sort of suggesting that this angle would be some unknown, only revealed by taking the measurement after setting the gap correctly with feelers...but 52 degrees is 52 degrees!

Next question - if the gap can vary between 14-16 thou, how many degrees will this equate to, +/- from the theoretical 52 degrees?

Maybe that was the original point....a 14 thou gap, a 15 thou gap, and a 16 thou gap - all within tolerance, would have slightly different dwell angles, right?

[weeds]

a tip I was given many years ago when setting points is......stick a piece of paper between the points rotate the engine til they close than drag out the paper.........this removes the oil/grease film that was on you hands and feeler gauge that may have ended up between the points

[Scallops]

a tip I was given many years ago when setting points is......stick a piece of paper between the points rotate the engine til they close than drag out the paper.........this removes the oil/grease film that was on you hands and feeler gauge that may have ended up between the points

I'll do that tonight too! Thanks.

[Hoges]

Small bottle of fluorescent "poster" paint preferably bright orange (bottle will last 30 yrs!), fine paint brush .. (from a kid's paint set). Use to mark TDC on pulley and reference point on engine cover. Inductive zenon timing light (SCheap $60), vacuum test gauge to connect to intake manifold, tach-dwell meter pref analogue one so you can watch the behaviour of the needle rather than a jumble of changing digits e.g. Dwell Tachometer | eBay (http://www.ebay.com/bhp/dwell-tachometer)

Read also Ignition Timing - Les Bengtson (http://www.custompistols.com/cars/articles/ignition_timing.htm) it's very informative, gives detailed instruction on both static (test lamp) and dynamic (timing light) timing and applies to the Land Rover engine as much as to the old MG under discussion

Re carby: . You can set the idle screw watching the tach (0-1000rpm range) and vac gauge and listening all at once and get a pretty accurate position for it. A small dab of Loctite (can't remember the exact one) on the idle screw thread once it's set will keep it in position.

To successfully set the carby, first make sure the vacuum advance tube is firmly attached to the base of the carby or wherever and also to the distributor otherwise you'll get air sucked into the manifold leaning the mixture.

Set the throttle idle adjustment screw to the correct idle speed. which means you need to get the timing set correctly first. Then as you screw the idle mixture screw in 'slowly', you are leaning the mix and the engine will begin to run a little rough. If you keep going the engine will stop.
Take note of the position of the screw at the point where you notice it beginning to slow and run rough.

Then slowly screw outwards thereby making the mixture richer. The revs will pick up but as you continue the mix will become over rich, the revs will again begin to drop off and instead of a steady beat, it will "hunt" as it does when you put on too much choke.. brrrm ...brrrm...brrrm instead of an even bom bom bom bom etc:eek:;)
Note position of screw. Now turn screw back the other way so that it's in the mid-point between the extremes.

Now use the tach and throttle adjustment screw to set idle at correct speed as necessary.

It's "real" mechanics stuff ---enjoy it!!:D

[Hoges]

See also http://www.aulro.com/afvb/technical-chatter/19085-4-cyl-motor-2.html

Inc. found a reference back in 2006 that the dwell was 60 deg for the Series 1 engine...
cheers

[Scallops]

Always 52 degrees - or around 60 +/- 2 degrees for Series engine? Probably time to go and find out for myself....

[Hoges]

Definitely not always 52 deg. That may be a reasonable theoretical number to get started but not in practice...

My "little black book" "Hawk tune up guide" Published in 1975 has tune up specs for most USA/European/ Asian vehicles . E.g MG variants 1963-72 listed as 60 deg dwell; Toyota corolla/corona 52deg; Rover 2000TC, 2000 auto 1965-70 60 deg; Triumph Sptifire 1971-72 4 cyl Mk4 42 deg; VW various 197172 1600cc 44-50 deg etc
It all depends on the state of tune, as well as the electrical characteristics of the coil etc
cheers

[Scallops]

Well mine is 46.5 degrees. Hardly varies at all ....maybe 1/10th degree lower, but pretty much constant. What to say?

As for setting my carby - I dunno - it's not playing the game. See - my Series 1 handbook says to turn the idle screw so the revs are higher than normal, then let the mix screw out (richer) until it hunts, then screw back in till stable, then lower idle again.

Seems to be so much variation in where I could estimate this that I can't tell if it's even close.

Doing the Martin method only seems to result in rough idle, and it needed richer....guess I'll just have to plod away.

On a sadder note, in order to try to check my mix setting, I took out plug #1 to check the colour, and it appears to be wet....looks like oil, so now I assume something has been buggered on a new engine build.....sad Scallop. :(

[Scallops]

My mix could well be too rich....I read that this can cause "wet fowling".....if mix were the reason, wouldn't all the plugs be wet? I just find it hard to believe that 400 odd miles on a not properly tuned engine has wrecked something....

[marting]

Firstly Dan I expect that the wetness on the plug is fuel. You are only adjusting the idle mixture here, once the throttle is opened fuel is drawn out of the main jet by the air passing through the venturi and the idle circuit is bypassed. If there is that much oil in the cylinder you would have blue smoke out of the exhaust.
I assume the main jet has not been changed, so regardless of the idle quality or mixture, once driving the mixture will be the same as before.
In regards the idle mixture setting, without getting too technical, simply try to find the smoothest idle. This will be the correct, or close to, mixture regardless of position of the mixture screw.
Cheers, martin

[Scallops]

Well, I appreciate everyone's help, but I am totally frustrated and confused. I guess this is why the internet rarely produces mechanics.

[Killer]

Hang in there Dan, practice should produce a great mechanic.:)

Cheers, Mick.

[Timj]

Hi Dan,

As Martin said just back there you seem to be a little bit confused about what the mixture screw adjusts. It only adjusts the mixture for idling.

Inside most carburettors there are three separate circuits that work together, the idle circuit, the main circuit and the acceleration pump circuit. The idle is only in use when the throttle plate is closed or almost closed. In this situation the normal carburettor circuits can't work as there is not enough airflow and petrol put in above the plate will not necessarily work as well as when the plate is open. Therefore idle circuits are separate and usually put the petrol in under the plate. Pretty much as soon as you open the plate and you raise the revs above idle you start to use the main circuits though the transition is usually gradual, not an on or off situation. All this is controlled by airflow and the resultant vacuum that creates. The main circuit which is used during all normal running is controlled by fixed jets that can be removed and replaced with different ones but are mostly not adjustable in place (some carburettors do have adjustable main jets but the Landrover carbie is not one of those). So what you are adjusting with your idle mixture screw is only used for a very small part of the running of the engine and is very, very unlikely to have damaged anything. The accelerator pump circuit just gives an extra squirt when you very first put your foot down on the throttle so again does not effect general running though may cause stumbling when the accelerator is pressed.

There are a number of different ways to set the timing on the engine and all of them work if you know what you are doing. I can set timing with points without a test light as you just look for the spark and that is where you tighten up the dizzy. However I can see no reason to have points in this day and age. I don't really care what the "purists" would have to say about that :) but why not put an electronic module in there and never have to worry about setting points again? Can't even be seen from the outside so no one realises you have changed anything but you get a much more reliable set up.

And the way that Martin suggested for setting the idle mixture is a perfectly good way and should result in a good idle if followed properly.

Cheers,

Tim.

[Timj]

And, if your dwell is at 46.5 deg then your points are open too much, which could result in poor spark. Set it to the correct 60 and see what happens, particularly if you have a standard coil then I would follow the standard setting. Higher voltage coils might require something slightly different (perhaps the 52 earlier suggested) but again, put an electronic module in there and forget that dwell or gaps exist :).

[wrinklearthur]

I don't have a dwell meter so don't use one.
Look at the back of the engine and you will find a cover on the top side of the flywheel housing swing the cover back and you will see a pointer and that coincides with marks on the flywheel.

First set your points to 15 thou", turn to each lobe in turn and measure each one looking for any variation due to wear in the distributor, reset the so the 15 thou" is the average and then put the 4° advance mark on the flywheel so it meets the pointer.

The slot in the clamp holding the distributor body should be halfway and the vernier set on the large mark, with the main clamp loose turn the ignition on.

Then turn the body of the distributor so that you move it the same direction as the rotor so when the points are closed move it slowly back the other way towards the direction of the rotation of the rotor button, listening carefully for the click as the points break open, check by softly wiggling the rotor shaft you should hear the points arcing at that point, tighten the clamp off and arrange your leads to suit the firing order.

Then go for a drive.

Oh that excess fuel, check the level of the fuel in the float bowl, before mucking about with jet settings.
.

[Scallops]

Well, had a better day with the little one today. Trial and error adjusting the gap set screw, put the dissy cap back on, start her up and get the dwell to as close to 60 degrees as I can.

Took about 20 goes....

Sitting on 61.6 degrees now. Ran out of light and sense of humour trying to get her just below 60.....maybe try another day

Played around again with idle mix and finally got her idling sweetly! The wetness was fuel. Appears OK now.

Took her for a drive, now back home.....she's running like a Boss!

I've got 2 sets of points to run through, and when I have I'll move over to electronic ignition. It's a suggestion that I've had from more than 1 trusted soul.

Thanks everyone for taking the time and effort to help me - again. I appreciate it.

https://www.aulro.com/afvb/images/imported/2014/02/964.jpg

[Hoges]

Don't sweat on the numbers. 61.6 deg is more than close enough. Most dwell angle specs are +/- 3deg. The 60 deg figure from Land Rover is a compromise which is arrived at after many hours of testing. You've done well!!:D

[Scallops]

OK - now setting the octane selector.....I have these instructions.....

"In addition to automatic timing advance and retard mechanism, the distributor incorporates a hand setting control, known as the octane selector. This is a vernier adjustment attached to the distributor, fitted with a sliding portion controlled by an adjusting screw and a calibrated scale marked R (retard) and A (advance) with a number of divisions between. The standard setting for the ignition is with the long line of the scale on the sliding portion against the mark on the selector body, thus leaving one division further possible advance and four divisions retard."

Makes absolutely no sense whatsoever.

1. Where is this "long line of the scale" - I have a double ended arrow with A and R each end.
2. Mark on selector body? It's a wheel - there is no mark on it. What does this mean?

You'd think across the entirety of the internet, there would be some simple diagram explaining this....but I can't find one!

[Scallops]

Well, hats off to my mate Killer.....tap a tap tap on the door, 30 seconds before my final grille badge auction was to expire on eBay (!) mind ......with an explanation....

https://www.aulro.com/afvb/images/imported/2014/02/404.jpg

The graduated lines are in the middle of my pic.....between the vacuum advance and the AR arrow. I can see them now with a bit of a clean up! How good is that Mick? The lines appear!

Thanks mate! I guess the rest of the Landy Universe already knew this but it's a revelation to me.

[wrinklearthur]

OK - now setting the octane selector.....I have these instructions.....

"In addition to automatic timing advance and retard mechanism, the distributor incorporates a hand setting control, known as the octane selector. This is a vernier adjustment attached to the distributor, fitted with a sliding portion controlled by an adjusting screw and a calibrated scale marked R (retard) and A (advance) with a number of divisions between. The standard setting for the ignition is with the long line of the scale on the sliding portion against the mark on the selector body, thus leaving one division further possible advance and four divisions retard."
1. Where is this "long line of the scale" - I have a double ended arrow with A and R each end.
2. Mark on selector body? It's a wheel - there is no mark on it. What does this mean?

If you find yourself a older distributor as I don't know if a new one has the marks ( I don't have access to a new one to check and see if those marks are there), you will see on a old distributor that the vernier adjustment is on the sliding potion where it passes through the body of the distributor with the thumb screw adjuster at the end of that slide.


You'd think across the entirety of the internet, there would be some simple diagram explaining this....but I can't find one!
I sympathise with you on this, as I haven't found any info on any sites for Land Rover engines either and now the good news, have a look for information for the same style Rover car engine.
I think it's on a Rover car restoration site and it's part of the owners handbook.

Still takes a bit to get your head around because of the shift of the refining of petrol over time, I believe the octane rating is offset by other additives now days, I wish there was some easy explanation about this.
.

[Timj]

With the quality of the petrol that we have today I don't think there is a lot of use for this. It was designed so that if you were in an area that had poor quality petrol you could retard the timing without needing to change the position of the distributor and therefore mess up the overall tune. The same thing could be done by putting marks on the base of the distributor that would allow you to move it a set amount and put it back again but it would be difficult to get a fine adjustment that way.

If you are running a lower octane fuel (than that at which you have already tuned your engine) you may need to retard the timing to stop pinging and if you are running higher octane you can advance (though this is not as critical as the vehicle will run fine without). Please note that if you have set your timing to the book then advanced it until you get pinging then bought it back until you don't you will be pretty much set up for the quality of petrol you tuned with. Any adjustments are then made from the known quality of petrol which is very much standard across Australia. Ethanol may vary this slightly but you should be avoiding ethanol anyway if you can.

Cheers,

Tim.

[Hoges]

My nephew has a 1928 Chev which he has fully restored. He told me recently that he, and most members of the club have discovered over the years that Shell V power (98 Oct) works best in their engines. It provides a very stable burn and performs better in the low compression motors than other brands/octane ratings. Some of these vehicles have manual advance/retard levers behind the steering wheel for controlling the spark.

A vernier was standard fitment on the Lucas distributor fitted to millions of engines of British origin in the 50s and 60s especially. Once the point gap was correctly set, you loosened the clamp holding the distributor, rotated the distributor body to get the timing as close as possible, tightened the clamp, then used the vernier as a micro adjustment in conjunction with a timing light to get the "dynamic" timing spot on. As mentioned, you could later retard /advance the ignition a couple of degrees depending on whether you filled up with "standard" or "super" grade petrol.