With the rolling road appointment at Peter Burgess coming up the high idle RPM issue still bothered me. And while cleaning up and sorting parts last weekend – I found a HIF4 rebuild kit I bought a few years back. This kit was intended for a second pair of used HiF4 carbs – but never opened. After an extensive bath in the Ultrasonic cleaner, these carburetors were just collecting dust.
The idea was to have a fully rebuilt second pair of HIF4 available in case Peter would find a major issue with the ones I have in the 18V. Personally, I prefer the HIF4 over the HS4. They are simple, reliable and easy to adjust. The integrated float prevents potential fuel starvation in curves or bumps. It is usually also less prone to leaking and has never caused run-on issues.
For anyone rebuilding the bushes are also a lot easier to cope with when they need replacement. This will be a topic for another post – along with reaming. But this got me to another benefit – the rubber seals for the throttle shaft. For most HIF4 and HIF44 I have done so far – just changing the shaft and seals was enough.
There were two three things I wanted to be sure about. A) o-Ring and the thin paper seal of the choke mechanism have to be in place. B) throttle plate (I choose ose the one without valve) needs to fully close and c) seal for the main throttle shaft need to be in place
The rebuild kit also includes the washer for the jet bearing. While I replaced them I believe that this is an item that might last forever. The ones I took out looked always perfect. In the various diagrams you find online the needle seat sometimes is shown without a washer. The rebuild kit also does not include them. I ordered a few from a shop that does sell them separately as the MGb workshop manual includes them. Don’t overtighten the seat – otherwise it will snap off easily. Ask me how I know….
It is important to make sure that the o-ring seal for the fuel enrichment screw is renewed – they were brittle on all of the HIF carburetors I have now rebuilt. Another benefit of the HIF4 is the fuel temperature sensing adjustment of the jet. This needs to sit correctly on the fuel adjustment screw. During assembly already make sure that the jet is set to base position.
Some people say they don’t like the HIF4 because it is impossible to adjust the float when the carburettor is in the car. True, but to be honest – adjustment is done easily during rebuild. A straight edge across the base and the middle of the float needs to be 0.5-1mm below. Do this against a light source – super simple to set. Once done – no need to check it again as far as I can tell.
The new seal for the float chamber needs to sit in the groove and the baseplate needs screws with spring washers. The chamber for the piston has three screws – those are installed without spring washers. That’s basically it. After I finished the spare ones I repeated the procedure and double checked the ones I have on the MGB. Main reason for this was to validate that the throttle plates close fully.
In my next post I will update you on my trip to Peter Burgess and if the carbs where any good
Fixing C6622 
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