[AussieRodney]

I have a 1985 1.3 Sierra that recently had some work done on the carby because it was full of crud. It went back again after that when it refused to idle & the mechanic took even more crud out of the idle jet. On both occasions, he mentioned that it would eventually need a rebuild. Since then it has been running OK. Yes, I can actually do 110 on the freeway on LT tyres.

I've also had the aircon re-gassed & that works too! However, pushing the loaf of bread at 110 with the aircon on makes it struggle a bit. But I have found that there is a spot on the throttle pedal travel, right down near the floor, which provides a noticeable surge of power, regardless of how hard the donk is working. It's enough to pull it from 100 to 110 within a few seconds.

Is this the second jet I keep reading about in here, cutting in?

[FullyZooked]

Sounds like your pushing into the secondary's. When jetted correctly the secondary should pull strong and provide a good "boost" in power.

[skyman]

Do you guys have a vacuum operated secondary, or is it done with linkage?

[want33s]

Under light throttle the engine is fed air through only one barrel of the carby.
Under heavy acceleration the manifold vacuum is used to pull the secondary barrel open, giving increased performance but less economy.

[skyman]

We do a modification here to allow the secondary to open mechanically, instead of with vacuum. It gives more power, but has the trade of of a "binary" feel at half throttle. Economy is the same if you can keep your foot out of it.

[FullyZooked]

I'm not sure what answers you are after exactly?

One thing to check with your Vacuum operated secondary is that the Vacuum pot actually holds Vacuum. Around 4 out of 5 I have checked do not hold Vacuum. Same goes with Vacuum timing advance.

[skyman]

Well, what I was trying to suggest that he may be able to modify his linkage to operate the secondary, instead of using vacuum for better throttle response. if anything it is free to give it a try, and easy to undo.

When Zooks are down on power here the first things i suggest is looking at the vacuum advance diaphragm and vac lines, seems ours like to quit holding vacuum just like yours.

Now that I know the secondary diaphragm is prone to leaks I will start checking that too.

[AussieRodney]

Thanks, FullyZooked. Now I know what I am dealing with. There are times when the economy loss is worth the power boost, like when there's a fully loaded semi barrelling up your bum!