Pre Ignition

just fitted another pinto mtr into my mk 1 cortina set timing to the marks as best i can and now ive got pe ignition and im not sure on how to fix it- switch the key off and the mtr wants to keep running i don't like it

i've set the points to book specs at 0.025thou and the dwell is at 38 timing at 12 degrees it seems to run and idle ok 900, 1000rpm
after being driven it dosent like being switched off it wants to run on

any solutions would be greatly appriciated
ps just bought a Accuspark for the dizzy this might help not sure

I would check that the carby is running on the idle circuit when the throttle is at rest and not holding the butterfly slightly open. This will cause it to run on as well. Or even the secondary butterfly slightly open.

Craig.

12 deg of timing should be the last mark on the balancer. Is there a need to run the idle speed so fast? On shut down you are more likely to siphon fuel out of the carby causing a run-on condition.

Thats why anti-dieseling solenoids are for, in the 70's everyone was afraid of high NOx emissions. They reduced the ignition timing but this screwed idle speed up, turning the idle speed screws up caused run-on.

Check your plugs too, visually and for heat range. They will show peppering on the porcelin if you are pinging.

You need to map out your timing. Run the engine at idle, 1500, 2000, 2500, 3000, and 4000rpm. Note what the timing is at those points. Also find out how much vac advance you have, just suck on the vac hose and read the added advance on the balancer. You will probably have to mark up the balancer to map the curve up.

Well i set the timing marks again set the harmonic balancer to the correct mark.

loosened the tensioner bolt removed belt just slightly moved the harmonic balancer then checked the cylinder head dot with the pointer and a slight adjustment probably 1 tooth on the belt

took the dizzy out and reset the dizzy so that the lobe of the of the dizzy and the points were open and carefully nipped up the dizzy and carefully put the belt on with out moving anything to much

she started first time and idled at 1,100 rpm dwell was at 38.6 and i didn't reset the points gap so it should have been at 0.025 of a though after a few minutes of idle turn off mtr and still over run ,so do it again recheck the marks all ok this time more attention to listening to the mtr and a difrent angle of the timing light it seemed no diffrent turned off mtr and just a little over run and dile at 900 to 1000drives ok dtill not right but better than before luck that it worked other wise it would have been $5.00 worth of fuel and a match ive had enuf ...

im using AP5FS NGK what could i use ?

1100 may be to fast,and as someone mentioned thats most likely the cause of the run on. Get the idle down,too much fuel is being inducted, anti syphon valve will help reduce run on but get the idle down as much as possible in the first instance.

NGK AP6FS plug is one step colder than an NGK AP5FS, but for a fairly standard (by the sounds of it) HC pinto,the AP5FS should be better suited really.
Like others have said, high idle speed's probably the main cause & 98RON is always a good idea, particularly in engines that used to run on leaded fuel.
Cheers, Jason.