6 replies to this topic

[johnpaul]

is there such a thing as a turbo only carb or can i use any hif 44 carb in my project?

im building an old school non ecu car with the keep it simple mind set.

cheers johnpaul

[nicklouse]

yes there is a turbo spec SU but i think you can mod a normal one from what i have read. sorry dont know the details though.

[Anthony30]

Think you just buy the turbo rebuilt kit, if I remember rightly.

[Turbo Phil]

You can use a non turbo carb. The main difference is the internal passageway to pressurise the floatbowl isn't there on non turbo carbs, but this is easily overcome by pressurising the floatbowl externally.

Phil.
 

[Retroman]

is there such a thing as a turbo only carb or can i use any hif 44 carb in my project?

im building an old school non ecu car with the keep it simple mind set.

cheers johnpaul

The early turbo HIF 44 had an external pipe from the bolt flange to the float chamber .(see photo)

 

It used manifold pressure from the flange drilling to the top pipe on the float chamber which is the vent / breather on NA carbs.

 

Later carbs had internal drillings to allow manifold pressure into the float chamber.

 

So you can use any HIF44 and either drill the bolt flange, manifold or a manifold spacer and connect to the top pipe on the float chamber.

 

[Ethel]

The external pipe is a bit of the "part throttle weakening device". Some non turbo carbs also have it, the passage Phil's referring to comes through the rear gasket face in to the plenum outside of the flow restrictor that creates the pressure differential for boost sensing.

 

The one that breaks the symmetry here:

 

It does connect to the part throttle jobby, but there's another flow restriction in the pipe the hose is on, making it unsuitable for boost signalling. The vent/overflow pipe is the one below the hose (needs sealing off when running boost, Metty's had a solenoid valve at the other end of the hose). You could use that, and to add to the confusion, if there's no part throttle device the vent pipe takes its place and the lower pipe is omitted.

 

The other main difference is the better seals on the throttle spindle. Also a beefed up float to resist being crushed and improved float valve - which can also be found on some non turbo carbs.

 

Oh, and the clamp and groove to secure the piston damper.

[Turbo Phil]

is there such a thing as a turbo only carb or can i use any hif 44 carb in my project?
im building an old school non ecu car with the keep it simple mind set.
cheers johnpaul

The early turbo HIF 44 had an external pipe from the bolt flange to the float chamber .(see photo)
 
It used manifold pressure from the flange drilling to the top pipe on the float chamber which is the vent / breather on NA carbs.
 
Later carbs had internal drillings to allow manifold pressure into the float chamber.
 
So you can use any HIF44 and either drill the bolt flange, manifold or a manifold spacer and connect to the top pipe on the float chamber.
 

That's just nonsense. You're talking about the part throttle lean off pipe. All turbo SU's have this. The floatbowl is pressurised internally as I mentioned above. The plenum contains a restrictor before the carb to cause a pressure drop accross the jet, and hense why the pressure reference for the float bowl is taken before this restriction where pressure is higher.

Phil.