I have twin 1.5" on my Mini but they are from a MGB.
How can I block the advance and air holes as am using non vacuum advance dizzie.

A vacuum cap would work, just get some the right size
https://outlawspeed.com.au/shop/mg3704

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Once again 'timmy' your insight is very helpful.

I run a HIF44 that had the engine breather air hole. I got a piece of aluminium rod the right size and araldited it into the tube, then neatly shaped the inside to match the carb bore so there wasn't any interruption to the airflow.... because, you know, it might gain me 0.0002 bhp

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did I tell you that I won a trophy?

Check the float bowl angle is right . 30 deg not 20 deg

Repco usually have vacuum caps the right size.

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1986 Mayfair (998 auto), 1974 S, 1974 Van, 1972 PMG Van

Test... Don't Guess

Better off getting a vacuum unit for your dizzy.

Cheers, Ian

This has been addressed.

What is the argument for vacuum dizzy?

If you want to keep it a genuine cooper S then they had a non vacuum distributor

The vacuum adds timing at low load to increase economy and part throttle response

You’ll get just as many mini people to tell you to take if off as will tell you to leave it on. Another mini topic for endless debate!

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Vacuum advance is fuel economy device. For race only forget it. However, at a steady cruise (I live in the bush) you can expect up to a 30% reduction in fuel use (measured tank to tank). If you're not running exclusively on a track then I don't see the downside.

1.5 SUs are not genuine Cooper S anyway so having gone that far why not use other improvements.

Maybe those who argue against them haven't had access to the expertise to set it up properly ...or are just repeating "received" wisdom.

Cheers, Ian

I was under the impression tht the economy savings was more like 10 to 15 % thn 30%. Having had both on a more sporty engine I am happier with non vac advance. The performance and response throughout the rev range is better than with a vac advance.
However I respect other peoples opinions and experiences, life would be boring if we all thought the eame.

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Cheers Dave.

Once you have wide open throttle the performance should be identical as there will be very little if any vacuum. As far as I can tell, adding timing with the vacuum advance only brings advantages to a road engine (provided the mechanical and vacuum advance is correct for the engine). It does bring a slight complexity for race engines, and seeing as they are pretty much only run at full throttle & have wild cams with low vacuum, you won’t see any advantage with vac advance

I got an OBD2 scanner for my Mazda as I was curious how the advance is mapped against load in a modern engine. At 3000rpm in 4th gear the timing varies from 17 degrees at full load, all the way up to 55 degrees at low throttle cruising. Obviously most modern cars are mapped for reliability and economy over performance, but it does go to show how much you could be missing if you remove the vac advance on a distributor car (and mine is disconnected at the moment!)

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I could not disagree with Steam's comment re varied opinions and experience. The 30% I quoted was based on well over a year's worth of log book entries so is my personal real world experience and not an opinion.

I can't comment on performance before and after but I don't remember any significant seat-of-the pants concerns.. Mind you, we also tampered with things like needles etc so some of the benefit may have to be allocated there.

Cheers, Ian

My experience with many old Lucas dizzies is the vacuum advance plate gets loose with wear, rocks about, giving spark scatter and varying dwell.
I've fixed a few (pun intended) by tack welding the two plates together and tossing the vacuum can.
In the case of my brother's Hillman Imp (25D dizzy), fuel economy improved along with performance.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.