Spark Knock

[MK1_Ben]

After my recent non running issues, the car is now running fine however;

It pulls fine through every gear, no hesitation but does idle slightly high. The timing is spot on but the dizzy isn't set up perfect (which is the cause of the idle I believe).

It has developed a really light tapping/knocking (not a heavy/bottom end knock, a top end tapping noise but heavier than the sound tappets make). Am I right in thinking this is spark knock / pre ignition or the likes due to the dizzy not being set right? It only happens at high RPM, idle low and med the engine runs sweet as a nut.

Also, if it is spark knock. Would it be fine to drive it 20 miles (home) at low RPM?

[John]

Pinking! (gotta love the 80's! lol ) get the timing checked with a strobe :)

[MK1_Ben]

Thanks for the response :)

If I keep it at low RPM (where it doesn't "pink") for the 20 mile commute home would it be ok? Then I can take it to a friends who's better at setting up the dizzy timing than me.


You must spread some Reputation around before giving it to John again.

[Jack]

Or dieseling lol

So long as you keep the engine off load and keep an eye on the temp it should be ok to drive a short distance. Try not to mash your foot down to keep it at low revs as that'll make it pink even more - 3,000rpm at light throttle is better than 1,500rpm at 90% throttle

[MK1_Ben]

Or dieseling lol

So long as you keep the engine off load and keep an eye on the temp it should be ok to drive a short distance. Try not to mash your foot down to keep it at low revs as that'll make it pink even more - 3,000rpm at light throttle is better than 1,500rpm at 90% throttle

It has been running hotter than usual, however it's only went up to just below the middle mark, but it does it alot quicker than usual. (chugging along at motorway speeds it used to sit halfway between cold and warm).

It sat running for 30 minutes last night and never went above the middle mark, and driving it 20m to work this morning it didn't even reach the middle mark (as above, when driving like a nan it cools down).

[mowgli]

is the advance retard mech working on the dizzy??

[MK1_Ben]

/ is not very good with older Engines as you can tell.

I'm guessing the advance retard mech is the 2 components on the dizzy with springs on them, which when spun at higher RPM open more?

If so yes, they're like new. The new dizzy came with a spring on each part on it though, whereas the old one only had 1 spring but still moved the other.

[mowgli]

no the thingy with the vacuum pipe from the manifold.. you can test it by pulling the pipe off from the carb end & sticking your finger over the hole(on the carb) and then sucking the pipe. if the engine note changes, then the mech is working ok.. if not, then the diaphragm inside is holed, and it isn't working.

if the springs/pins are in good order, then you are lucky. back in the day. they were known to wear the pins thru, and the flying metal could chop the cap in 2

[MK1_Ben]

It was working fine previously so it can't be that.

I just think the dizzy position is wrong, which is why it's idling high + pinging. In theory I just turn the dizzy the opposite way a small amount, test it through the rev range and repeat until it doesn't ping or bog down?

[mowgli]

and that method is the reason why they call it tuning... i'm being serious, you adjust it by ear, if it sounds right, it is right..

[MK1_Ben]

Nice old learning curve retro cars are haha.

Guess I'll just give it a go later, general opinion from other people I've asked too is that it's definately the dizzy timing making the high Idle and Ping. So I just have to retard it tiny increments at a time until the knocking is non existant (the same as a Knock sensor tells the ECU to do on a modern Engine).

[mowgli]

well, with it running, just undo the clamp nut & twist it a bit anti clockwise (viewed from the left) and see what happens.. it should make a difference straight away

[MK1_Ben]

Thanks again :)

Must have been the 999th time you've helped me with my car this past month.

Thanks to everyone else who has contributed too :)