Ignition timing for a non standard 1098 engine

[mu0u207b]

Does anyone know how to find the correct ignition timing for a non standard modified 1098 engine. The engine has a HIF38 carburettor with water heated inlet manifold, K & N air filter and electronic ignition. Ive tried trial and error using the vernier timing adjuster on the dizzie, but still not too sure on the proper method of finding the correct timing. Has anyone got similar modifications to their engine and have a value for degrees of BTDC. Any help would be wonderful. I do have the David Vizard tuning the A series book but this is fairly general for the A series engine and does not have a method for finding the timing value.

[Jefftav]

Hi, I have a similar setup on my Minor and I don't have an exact method of setting up the correct timing - a visit to a rolling road is really worth it but to get started try to start the car and take it for a drive to warm the engine up fully.

Switch off the engine make a mark with tippex or similar on the Dist cap and Dist Housing so you have a reference mark and slacken the distributor so that you can rotate it by hand but not so slack that it moves on its own. Then restart the engine and turn the distributor anti-clockwise until you hear a misfire and mark the housing again and then rotate it clockwise until you again get a misfire and mark the housing - hopefully you can then set the distributor inbetween the 2 new marks and the car will run without pinking. I then got hold of a dwell meter and measured the dwell angle at 57.8deg at 800rpm. I have run with this for a while and the rollong road place reckoned that this worked OK and didn't see the need to alter it. He did say that the heated manifold doesn't help much and I should take it off - I haven't as it all works OK for me.

Also check that the distributor advance mechanism works - I can usually hear a click when I detach and reattach the vacum advance on the carb but I am sure there will be a better way of confirming this - maybe someone else will know??

Cheers, Jeff

[rayofleamington]

Also check that the distributor advance mechanism works - I can usually hear a click when I detach and reattach the vacum advance on the carb but I am sure there will be a better way of confirming this

If you suck on the advance pipe the points mechanism should move. If youseal the pipe (with your tongue ) it shouldn't go back - if it does then the diaphragm is leaking.

[ColinP]

Jeff,

The dwell angle is another way of showing you have the correct points gap (it's the angle during whcih the points are closed).

Mine measures at 58 degrees (Gunson), on a standard engine with the correct points gap (new points).

It doesn't affect when the spark happens - that's set by turning the distributor.

Colin

[Cam]

I have always found 6-8 degrees to be a pretty good setting for A-series engines. I know the book says 3-5 degrees, but mine seems happier at 6-8.

[turbominor]

set mine up by turning idle up to about 2000 and adjusting dissy to give the max rpm then road tested to check for pinking..

Going like a train now

Will be back on rolling road as soon as i can drive her properly again

[Peetee]

My 948 with 12G295 head and 1.5" carb was set at 6° @ idle.
There are so many variables based on which modifications you use and the way they all interact that the only way to find the TRUE answer is to have it properly set up. Go far enough with the modifications and you may well find that it's not the ignition timing at idle that needs adjusting but you need a distributor with a modified advance curve.

[ianselva]

The points gap or dwell DOES change when the spark occurs - too small a gap and the spark is earlier , too big and the spark is later. Not much admittedly ,but it will change it . so set the points before you start checking the timing.

[rayofleamington]

The points gap or dwell DOES change when the spark occurs - too small a gap and the spark is earlier , too big and the spark is later.

Only if you adjust the points and forget to reset the timing - ie if you reset the timing then the points gap has no bearing on the timing. To my understanding, the dwell angle itself is required to get a strong spark (the field in the coil needs time to rise and fall)

[ianselva]

Do you want to re-think that ? try with exaggerated differences and check you will find that it does change the timing when ever you set it . It is goverened by the points touching a cam , obviously the further the points heel is away from the cam to start with , the further the cam will turn before moving the points. granted it is only a fw degrees.

[ericwork]

before we go too far down the points road, the car has electronic ignition, maybe it has no points.
I have set my electronic ignition to 6Deg and all seems okay so far.


Eric.

[rayofleamington]

Do you want to re-think that ?

As mentioned - if you reset the timing (which moves the points up to the cam by moving the distributor), then the points gap is taken out of the equation.
My point was that the gap is only important if you go and change the gap later on without resetting the timing.

Anyway - we're getting off topic as usual

[mu0u207b]

I assume that with electronic ignition fitted that the dwell angle is not a factor. The electronic ignition is the Lumenition magnetic type that fits all within the dizzie cap. Should the plug gap be set as standard or should i open up the gap, and if so what gap size do people recommend.

[Cam]

I set mine to standard when using an Aldon Ignitor electronic ignition module (similar to your Lumenition).

[mu0u207b]

Ive tried timing the engine by turning the dizzie to a position where the revs are at there highest and knocked it back slightly and test drove to find fairly good acceleration with no pinking. I have then checked the new timing with a strobe light on the pulley wheel notch and found it to be approx 20-30 BTDC. Is this value excessive as other peoples quoted values are between 8-12 BTDC. I also tried to retard the ignition to these suggested values and found the engine to be sluggish and rough idling. Is there something drastically wrong. I have fitted a duplex timing chain within the last 10 months and was very careful to line up the two dots on the cam shaft cog and the crank cog.

[Cam]

If you had the vac pipe connected from the carb to the dizzy when you took the measurements and/or the idle rpm was a bit high then you could have obtained those readings. Have you tried setting it statically?