yeppo... and if we wanted a gap, why would we bother rebushing them at all? I've got a lovely gap as it is - through the shaft holes

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did I tell you that I won a trophy?

And on a cold morning the jet blast of air rushing through the gap will freeze and cause the throttle to stick.

Some good points there.
I think I'll strip the carbs back and move the bushes in.

But Simon if you do have a proper milling machine and vice handy don't worry about a jig, if you don't have a good machine though a jig would be a must.

the machinist at work and I played around with my test carb on the mill today, just using a square and the mill vice. Getting the mill bit dead centre on the original shaft hole is a major pain, the hole isn't centred on boss that it goes through, and once it's clamped in the vice, there isn't much else to work off

And as you said earlier, making the 2 holes line up when they can't be machined all the way through from one side to the other pretty much means a jig is a must...

and I bought some bushes, but Midel sent the wrong ones, and are out of stock of the right ones

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did I tell you that I won a trophy?

usually the holes wear oval, so when you bore the body, how can you be sure to bore the to the original centre of the hole ?

It does not have to be on centre. The shaft can be offset. As long as the butterfly closes it does not matter where the shaft is.

Holley carbs have the shafts offset deliberately so that the airflow will blow the butterfly shut if the linkage becomes disconnected.

ok thanks