4 replies to this topic

[Pavel]

Hi Everyone,

Right I fitted a HIF 38 carb on a MG inlet yesterday to my 1275 metro engine since the old carb was beginning to give problems, and engine fired up quite nicely... At first there was black smoke EVERYWHERE, as the float chamber wasn't closing properly, so the whole carb came off and i fixed it.. after that ran quite nicely.

Using the idle speed screw i adjusted it as much as i could to about 850-900rpm, using an old Audi tachometer in the engine bay.. The problem now is the engine wanders up to about 1050 rpm every so often and back down... its really not running smoothly..

Can anybody help me figure this out?

Ignition seems fine since before that I had my weber and it idled smoothly (albeit at about 1600 rpm). I'll still probably be getting a electronic ignition set with new coil, leads, plugs etc.

Another problem I have is the connections to the HIF carb... there's at least 5 different nipples or take offs on it, and so far the only ones i have conected are the fuel line and the vacuum advance take off just before the inlet.. Can anybody clear up which of these should be connected where?

Thanks

[hammoj28]

When my brake servo started to leak it made the carb take in air and the car wouldn't idle properly. Your servo could have a leak somewhere. Take off the pipe from the servo leading to the carb on the servo end and put your finger over the end. The carb might run properly then. I have disconnected my servo at the moment as it is wrecked and I have blocked up the servo pipe to the carb. it runs fine now.

[Pavel]

Could it be that the engine is sucking air in at some connection on the carb that should be blocked? Since I don't have a servo now (servo take off is blocked)...

Also if there was an air leak wouldn' the engine rev quite a lot? It only changes RPM in minor increments and at pretty much regular intervals... vrrrr..drooom....vrrr...drrooom....vrr...drrooom!

[Dan]

What you are describing sounds like what is called induction pulsing, due to the 5 port head and the firing order and carb/dizzy setup interacting badly. It will vanish when you get it in tune properly as you suspect.
HERE is Mr Keith Calver describing how to hook up an HIF SU properly. Hope this helps.

[Madmax]

calver - god