Ignition problems?

[davidj]

HI,

My car has just passed it's MOT so is already for summer, or it would be if it was not running like a back of nails! Lots of popping on overrun and poor acceleration. Checked the ignition and dynamically it is set at about 20 degrees at tickover, approx 800rpm. Winding up the revs and it retards off the scale. This to me sounds a bit high to me, but as the engine was set up on a rolling road I don't wish to upset anything.

The car is fitted with Lumenition ignition and I have never had much success with static timing

Any suggestions?

Cheers,

David

[neilsjuke]

Check the earth
Neil

[types26/36]

Checked the ignition and dynamically it is set at about 20 degrees at tickover, approx 800rpm. Winding up the revs and it retards off the scale.

Well if thats true it will run like a bag of nails! it should advance with engine speed, which way does the pully mark appear to move? ....from the front it should appear to move left (anti clockwise which is advance)
Suggest you set the timiing to 10-12 degrees BTDC @ 800rpm then see how it pulls.

[davidj]

Yes it is true! From the front it moves anti clockwise as the revs rise. It does have a QED cam (a 420) fitted. Would this require the ignition to be more advanced than normal?

The engine was set up on a rolling road so I am reluctant to change if not neccessary. However, 20 degrees does seem very advanced.

Thanks in advance for any comments.

David

[types26/36]

Yes it is true! From the front it moves anti clockwise as the revs rise. It does have a QED cam (a 420) fitted. Would this require the ignition to be more advanced than normal?

Well if it is moving anti clockwise then it is ADVANCING and not RETARDING, advancing is correct but you were saying it was RETARDING OFF THE SCALE, retarding would cause all sorts of problems.(the pully mark would appear to go clockwise)
Sorry I don't know what 420 cams require as a static setting although 20 does seem quite a lot, one of the other guys with 420's could probably advise or even contact QED who could give a recommended setting.

[davidj]

My engine has three timing marks on the block at TDC, 10 and 20 degrees. At 800 rpm the timing mark on the pully lines up with the 20 degree mark and as the revs rise the pully timing mark rotates anti clockwise to 30 degrees +. It is difficult to measure as the timing marks stop at 20+! Yes, it advances not retards as I mentioned in my first email.

I asked QED what it should be set at and they said they did not know (!). Any one else with QED cams?

David

[gjz30075]

Did you try Brian's suggestion of setting the timing to 10-12 degrees at 800 rpm?
I don't think the cam profile is too radical to require 20 degrees initial. My cams have a .416 lift (I'm guessing the QED 420 has .420 lift) and I'm set at 12 degrees initial timing, at 900 rpm.

Greg Z

[davidj]

Hi,

Thanks for your comments; yes I tried Brian's suggestion and set the timing to approx 11 degrees and there was a marked improvement. The bolt holding on the dizzy was a little loose, so I guess it had drifted out.

However, it is still popping on overrun so I guess there is an air/exhaust leek somewhere, and the ignition light is not going off, so there may be a problem with the charging circuit as well!

Thanks for your help,

David