Ignition timing

[cfcrotweiller]

Hi guys,

I know this is a talked about topic, but I just wanted to ask something specific about timing the ignition by ear.
I've got the V8 running now but as the engine was half missing and has been rebuilt with old parts etc, the carbs are I think off slightly, idle and mixture might also be off but close (im getting a Gunson Colourtune and Carb balancer to rectify these two things), but I also think the timing is off.

Now I did the timing on my BMW 323i and she runs really well.

Am i right in thinking that if you do it by ear (and at idle), you basically rotate the dizzy until either the revs drop (in which case go the other way), or the revs increase but then starts to get a bit lumpy). Is the correct timing when the revs are at their highest and before the engine starts getting lumpy? This is usually when it feels its smoothest.

Should I be doing this with the vacuum advance hoses unplugged and repeat what I do above?
I have a timing light so I could actually do it from the marks on the balancer - I don't use this method too much as my Bimmer had a different balancer so the marks were useless!

Any suggestions greatly appreciated!

Meainwhile, here's the beast with a bit of throttle:
http://www.youtube.com/watch?v=rniYHNfGh-8

 

[rockdemon]

vacuum unconnected...

it's iterative. do the timing so it's at it's fastest point, get the mix right. then check the timing is still at its fastest running point. Then go for a drive. if it pinks retard a minute amount. When thats done then set the mix again.

Go round this loop a few times and you'll discover the sweet spot

Rich

 

[cfcrotweiller]

Thanks Rich,

That's sort of how I thought it would be but I haven't really read specifically thats it's the revs you look out for.

Might try and give this a go tomorrow, although I don't have the Gunson Colourtune to set the mixture, so this might not be bang on.

Cheers
Andy

 

[richj]

If your running on a C.B distributor get your points set first, preferably by a dwell meter.. All other settings will be false if it's not done from the beginning

 

[cfcrotweiller]

Hi,

Is the dwell meter to set the contact breaker points?
Can you not do this using the hexagonal screw sticking out of the distributor, and setting the contact breaker gap (when the contact is touching the peak of the hexagon below the rotor arm), I think set at .38mm from the book's spec.


Thanks
Andy

 

[richj]

Hi,
Yes the hexagon nut serves to adjust the points gap. It's useful because you can adjust them with the engine running. As for the dwell meter, it's the most accurate way to adjust points. It's measures the points angle in the closed position. Connect your negative (black) lead to a good earth, the pick up lead (red) to the negative side terminal of the coil. Make sure in dwell setting on the meter. Simply adjust until your somewhere around 26-28 degrees. You will probably get fluctuation from the readings, usually down to the distributor cam being slightly worn. Try and get a average figure and stop there. If it's too erratic then I would suggest going electronic (lumention)

 

[ghce]

I have always found it best to tune ignition by ear, but if you do this you really need to totally ignore the timing marks. When you look at the marks it really upsets your own internal "hearing and feeling" of the timing. Having said all that I am sure every ones abilities to do this vary wildly, it works for me it may not for you.
Having your carb closely tuned to correct is a wise thing to have so that you are not chasing your tail.
Hopefully when you have got to the correct feeling and sounding point if you run a timing light across it then it should roughly correspond to what the book says it should.

Graeme