Swoping from strombergs to Hif44, rover v8

I've just swopped to a set of Hif44s which were cleaned up, float hights, jet tube hights and throttle stops set as per lots of reasearch. The carbs were treated to all new seals and o'rings supplied in a genuine su kit.
My problem trying to set a reasonable tick over prior to checking the mixture.
The left hand carb will not respond to adjustment of the throtle stop screw, its pulling loads more air thhan the right hand one with the screw backed right off.
The only I can get the reves down is too weaken the mixture right off.
The piston is moving freely and lands with a nice clunk (same on both carbs).
The over run valve appears to be closed ok.
Should I fit new needles and tubes, or is there somthing i can try first, any hep much appreciated, cheers George


Well-Known Member
Did you replace or remove the butterflies? If so did you centralise them when you put them back?
Make sure that the fast idle screws aren't making contact with the choke cams and holding the throttle(s) open.

PS Are the butterflies fitted with emission poppet valves?
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I've not removed the butterflies and the fast idle screws are well clear of the choke cams.
The butterflies are fitted with the poppet valves. I've checked the one one the carb I'm having problems with, manually operated it and rotated it, given it a spray of wd40 and as far as I can tell its seated ok
There was no play in the butterfly spindles and I fitted the latest spec seals with the open side looking out (found a diagram that showed them fitted the other way around for turbo application's). Used a dab of grease when fitting all seals.


Well-Known Member
I've not removed the butterflies
Providing the last person who fitted them centralised them you should be OK then.

The butterflies are fitted with the poppet valves. I've checked the one one the carb I'm having problems with, manually operated it and rotated it, given it a spray of wd40 and as far as I can tell its seated ok
Personally I'd solder them shut, that way you know they're not going to cause problems. (Or fit solid butterflies). Engine vacuum overcomes the springs and increases the idle speed.


Well-Known Member
I guess you have to start looking for a vacuum leak, maybe on the bolt up flange, breather pipework, distributor vac pipe, manifold etc. Anywhere that carb can get extra air that is not passing the butterfly.
I don't feel needles and jets are the issue in a fast idle problem.


Well-Known Member
What Cobraboy and Harvey said. I doubt it’s needle and jet related. I’d be almost certain it’s a mis-alignment of a butterfly or a poppet valve issue. If the bushes or spindles are worn that can also cause the issue. The seals on the outside will reduce air being sucked past but a badly worn spindle or bush will cause the butterfly to not seat correctly.
Hi, i removed the carb and have checked the shaft and seals I cannot blow air into the carb past them. I centralized the butterfly when refitting however when fully closed if I hold the carb with the butterfly horizontal looking in at it from the engine side and spray WD40 around the edge it leaks past.
Should the butterfly form a perfect seal?
PS. I have read that the non popet butterflies as used on MGC and MGA Twin cam which were fitted with 1,3/4 SU's will fit the HIF44.
I intend to purchase a pair and to eliminate the popet valve as a potential problem. Cheers George
Hi Harvey, inthe Haynes manual it says to fit the butterfly and leave the screws slightly loose and operate the butterfly several times and then tighten the screws.
On the HIF44s i have the butterfly retains the shaft, there is no fastening on the opposite end to the opperating leaver so I let the shaft have a little end float in either direction so the butterfly would be able to self centre.
On another note I much appreciate your and others advice and time spent helping


Well-Known Member
I hope that you wound the idle screws right out before you did it. Once you've done that open the throttle fully by hand and then let go and allow the butterfly to slam shut due to the return spring acting on it, then without moving the butterfly, tighten the screws. Then screw the idle screws back in to give you a starting point when you run for tuning.