It Lives! Question about Vacuum advance and fuel ratio

[Nambo]

So I put petrol in it today and for the first time in five years heard my Stag running, started quite easily and no smoke or vapour from the exhaust.

I adjusted the ignition timing and noted in the book that you have to pull the pipe off the Vacuum advance, which I did, my question though is why?, for at tickover, the timing marks didnt move whether I had the pipe connected or not, it only showed a difference when I revved the engine, does this indicate a problem with my vacuum advance?

The other question, I have a fuel ratio meter, now the instructions say the ratio should be around 14.7 to 1
Now is this just for modern vehicles?, what ratio should the Stag run on?, I used to think back in the day the ratio was 16 to 1, though that is even leaner.

[Stagdad]

Mine idles at about 13:1 ,town driving at about 14.7:1 and motorway crusing 16:1. Hard exeleration you are looking for about 11.5-12.5,down hill overrun should go way up to 20:1+
Cheers Steve

[Nambo]

Thanks for that Steve, very useful.
Do you know what readings I should expect when my Holley moves from the smaller to the bigger bores?

[Stagdad]

Ah didn't know you had a Holley. When I had mine I had a very rich idle I struggled to get it better than 11:1 .cant remember what happened with the secondary's opening, sorry.

[Westfaling]

Vacuum advance is highest at idle. If you pulled the pipe and the timing/running didn't change it sounds like somethings wrong .Either a blockage or the vacuum unit on the dizzie.
You're supposed to block the vacuum line when you disconnect it otherwise it behaves like a manifold leak - if it made no difference I'd suspect a blockage.
Nick

[Nambo]

Ah didn't know you had a Holley. When I had mine I had a very rich idle I struggled to get it better than 11:1 .cant remember what happened with the secondary's opening, sorry.

My idle started off around 15.5:1 I changed that to the 14.8:1 did you try lowering your float heights?
I am correct in my thinking that the reading means 14.8 parts air to 1 part fuel? and the higher the number the leaner it is?

Guess I need a new vacuum advance then, mine advances a lot further when the pipe is connected but needs quite an increase in revs to do so. thinking about it, revs rather than just opening the throttle.
Do these cars have a mechanical advance as well?, I cant remember, the Luminition doesn't incorporate any advance does it?

Pete

[Stagdad]

Are you on the right vacuum port off the carb? That idle sounds very weak what main jets do you have? Think I ended up at 49's. Yes the dizzy has advance weights as well as vacuum.

[Nambo]

Are you on the right vacuum port off the carb? That idle sounds very weak what main jets do you have? Think I ended up at 49's. Yes the dizzy has advance weights as well as vacuum.

Yes, the tube on the right side.
I can enrich my idle if I so wish but it then started hunting, I figured 14.7 was to aim for and the engine seemed to prefer it there.

[flying farmer]

In theory the mixture shouldn't alter as the secondaries open. In practice there is normally a weakening at the moment of opening as it takes a while for the fuel to star moving towards the jet. This is felt as a flat spot.

When I was running on a 390 Holley I bought the vacuum secondaries kit which was a variety of springs to alter the opening time of the secondaries. I ended up using the stiffest spring which IIRC bought the secondaries in at something over 5000rpm. I could still feel the flat spot in second with the rapid rev increase (but this engine was in the much lighter TR), third didn't show the flat spot and anything after that would be licence losing anyway!

Neil

[Stagdad]

Yes, the tube on the right side.
I can enrich my idle if I so wish but it then started hunting, I figured 14.7 was to aim for and the engine seemed to prefer it there.

I ment the correct side iirc the Holley has a constant vacuum port and a timed port not sure where they are on the carb though.