pinking under load

[//no.comment]

Hey everyone,
ive got a problem thats got me scratching my head after fitting a new simmonbbc 45d distributor with electronic ignition.
Ive set the timing for best idle, but it pinks( noise like a ball bearing dropped on glass) when accelerating hard under load,
so i retarded it until it no longer does this but now the idle is poor, (idle is improved by sucking on the vac advance)

It seems as though the vac advance is advancing it to much for hard load conditions and causing it to pink, is there anything else to check for causing pinking?

Thanks
Andrew

[bmcecosse]

Vacuum advance cuts out under heavy load (when the inlet vacuum falls away) - pinking must not be allowed to continue! The idle should be set with the vacuum advance connected to the carb. Perhaps the connection to the carb is blocked - probe it with a toothpick - something like that. Where is the vac pipe connected on the carb?

[//no.comment]

ive retarded it so that it doesnt pink dont worry,
Idle was set with vac advance connected, distributor base plate moves, vacuum on carb clear.

just checked plugs they look ok, maybe just a little bit on the lean side, will give it a tweak and see if i can run with a bit more advance.

any other thoughts?

[bmcecosse]

Is there any indication from SBBC how much mechanical advance is built in to the dizzy?

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this is the unit http://www.simonbbc.com/bundle-deals/hi ... rris-minor
Though i am now running on a regular lucas coil as that one has been put into the landrover when that was having issues
no indication of advance but it will email them asking
Have tweaked the mixture and it now looks spot on at the plugs

[bmcecosse]

And is it any less prone to pinking now?

[//no.comment]

it still pinks at a good idle, with idle retarded it doesnt pink

simon bbc emailed be back saying its a 6/14/8 distributor advance, is this about right?

[bmcecosse]

I have no idea what that means....... If however it means there is 18 degrees of mechanical advance, then that is FAR TOO MUCH. Since that is dizzy degrees, and will be = 36 engine degrees. And since the max for a decent A series is usually somewhere in the 30/34 degree area - you wouldn't be able to set any static advance - possibly even slightly retarded. I suggest you ask what the figures mean.....