I have an Autolite 4100 1.12 on my 289 Windsor (I know the carby is a little too big for a 289) My problem is that I believe the vacuum advance outlet on the carby is Ported and therefore there should be know vacuum at idle. However, my vacuum advance increases over 20-30 degree when I connect the vacuum advance line to the distributor and thus raising idle speed. Appears to be no obvious issues with carby and I have rebuilt it twice and all appears okay.

I cannot see why the Ported vacuum connection has this much vacuum at idle (No matter how slow I adjust the idle) when it is supposed to be zero.

can you explain/assist

Many thanks

Mark

 

Might need a different set of weights and springs in the distributor.

You can also try and adjustable vacuum advance canister.

 

Yep thanks, been trying a bunch of stuff lately. Found an adjustable Vacuum cannister and trying various settings. Also adjusted the idle mixture screws with vacuum gauge connected manifold to try and squeeze as much low idle as I can get whilst car in 'Drive' to reduce the amount of vacuum advance at idle.

One other thing is that I have purchased two Venturi Bore adaptors which reduces the 1.12 size to 1.08 from the USA. Just waiting for them to arrive. As I cant find a used 1.08 Autolite at the moment I thought I would give them a go and see if it will be better for the 289 as I think the 1.12 carby is providing too much fuel and perhaps other issues which is affecting my issue. Will see how it goes.

 

Yeah I was going to suggest an orifice (bore) adapter since yours was ported but I figured the adjustable vacuum advance canister would be enough to counter it.

post up how it goes with the orifice once you receive it.

something else to consider, is the cam stock or does it have a performance cam? A performance cam with a longer duration could run timing in a higher range as well as pull more vacuum.