HIF or HS

[sii803]

Ok I have a 1275 from spridget, still sitting on floor and it has a pair of HS2s fitted to it. I'm not trying for masive HP ,55 would be fine. I want it to be simple and reliable.

I want to get rid of the HS2s and fit either a 1 3/4 HS6 or a HIF44. Already have new intake manifold, but havent yet decided what to do with exhaust, it could be either 1000 manifold, spridget manfifold or small bore extractors.



Is the HIF any better than the HS? I can get the HS much easier and chaeper in Australia. I also think it looks better under the bonet.

[bmcecosse]

The HIF is a superior carb - after all - it is a later model designed to eliminate some of the earlier flaws. The integral float bowl does away with spluttering on corners - which is a major benefit on Minis - not so important on Minor. Power will be the same to all intents and purposes - best of course if you can spend the time 'Vizardising' the carb - althougha single 1.75" carb is more than enough for an otherwise standard 1275. In fact - a single 1.5 would be enough for normal running - slight loss of top end power, but better mid range running. As you say - the HS model is more in keeping with the age of the car. An MG Metro (or copy) alloy inlet manifold is by far the best type to use for a single carb - and don't connect the water heating!

[JimK]

Quite a few people connect the manifold heating into the cabin heater return. You tend to need the two things on the same cold mornings, anyway.

[bmcecosse]

But any heating reduces the charge density. The twin manifold has no water heating!

[sii803]

Thanks for the feedback. I have heard it mentioned that the HIF is easier to tune, has better temperature compensation and is more ecconomical. Anybody able to colaborate this, or blow it down?

bmcecosse - I might be going for slightly more horsepower, just dont want to compromise the durability. When recently visiting the UK i found myslef an aftermarket aluminium manifold which I think is ment to be similar to the metro one:)

JimK - I problably wont need the water heating, as it is rare to have problems with freezing here in aus.

[bmcecosse]

Yes - the HIF is all of these things. Dunno about economy - one wee snag is that the spring loaded needle rubs on the jet all the time - so over the years it eventually ovalises the hole allowing more petrol to escape. You can compensate for this at idle ok - but when it's running more is going to come out than was intended. So - a new jet may be a good idea if you find the economy poor. Water heated inlet doesn't help with icing - it's too late! The icing occurs in the carb - only way to cure it is with hot air intake from over the exhaust manifold. And as you say - unlikely to trouble you!

[Roni]

The HIF does have a thing called an additional weakening device. This leans out the mixture when higher vacuum conditions exist (e.g. at part throttle cruise). When the vacuum vanishes, under acceleration etc, the carb reverts to full strength. This happens all over the needle range and should help the economy. For a fuller description of how all this works it is all explained in Vizard's book as well as how to build your own to fit to an HS.
If the carb is not new, change the jet and needle. They both wear especially the jet.

[Packedup]

HIF44 all the way if you have the option

Better cfm, better throttle linkage (if you get the one with the cam on the throttle spindle), better everything really.

The heated manifold does prevent fuel pooling on the walls through condensation (and helps warm up times a little too), but it frees up a fractional bhp improvement without it so not worth plumbing in unless you really really want to. I've run Minis with water heated inlets that I haven't hooked up, and found no problems with icing, economy etc, but then I've found no noticeable improvements removing the hotspot either on an otherwise standard car

[bmcecosse]

Oh the big V shows a very dramatic improvement in power when the exhaust hot-spot is removed - and the engine adjusted to take advantage. In fact - the difference in power of a Sprite 948 to a Minor 948 of the same era is almost ALL (a little is the straight through exhaust) down to the fact that there is no exhaust heating of the inlet charge - the twin 1.125" carbs in themselves are useless !