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Ignition timing - I can't get less than 12 deg at idle

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S

Swiss Toni

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Hi Chaps

First post after lurking in the shadows.....

I'm hoping for some insight on setting up ignition timing on my B7T works rally rep which I purchased about a month ago. 1st classic car and really enjoying it!

Its got got fairly serious engine on triple webers and just going through things.

Today was ignition day, new wires & plug caps, coil, cap, rotor, points, condenser, plugs, basically the works.

I set the idle when warm at about 800 to 900 rpm but I can't get the timing below 12 deg. The shop manual says 6 degrees is what it should be. Then distributor is backed of as far as it will go (the advance housing is resting against the steering column and the micrometer is set at full retard.

When rpm is increased it advances to 36 degrees which is in spec.

Took it out for a road test and runs better than ever, especially at higher rpm's.

Am I missing something?

Cheers
 
Usually, idle timing is spec'd at 600RPM with the vacuum advance disconnected at the carburettor (and the port plugged). If not that then maybe cam was advanced?
 
You may have not set the dwell correctly.???
 
The vacuum advance was still connected, so that is likely the issue.

Get it it to idle at 600 rpm might be another story with the cam I have......

I'll also look at checking the dwell, though they are a fresh set of points set to 0.015" gap.

Thanks.
 
If you can't rotate the distributor enough to retard the timing then you can pull and reposition the distributor drive gear.
 
Ignition timing will depend on the camshaft and the distributor your engine has been fitted with. Only if it has the original cam will it be six degrees, a BJ8 is 12 I think from memory. Also, of you have a hotter than standard cam, the advance on the distributor may have been limited. This is because at peak revs, you need say 38 degrees, but perhaps 15 at tick over.

I'd advise doing some research to get the exact spec for your car before altering the timing because where it was may have been correct and only the points might have needed checking/replacing.
 
I am experimenting myself with the ignition timing, I have a BJ7 with a Racer Brown cam in it.

It seems that from my Healey guru, Bill Rawles, that Big Healeys can be set at 16 degrees at tick over.

It sure revs better at that setting.

:cheers:

Bob
 
Bob, If a hotter cam has been fitted, 16 degrees is about right. The volumetric efficiency at tickover is not as good as the std. cam, that's the reason the plugs must be fired earlier. More important however is the maximum advance. Specified 36 degrees shoud not be exeeded. In fact a hotter cam gives improved volumetric efficiency at speed should need even less then that.
 
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