17 replies to this topic

[JamesW83]

Hi,

 

Fitting a stage 1 kit to my 998 Mayfair today: RC40 exhaust; Maniflow exhaust manifold etc. and all was going well until...I snapped a corner of the inlet manifold plate. Dealing with the stud nuts was problematic, i'd like to have had the carb and manifold all as a piece but it feels like there isn't space to do as one, unless anyone has any advice?

 

I didn't realise I'd snapped it, until I started it the engine and what sounded like quite a high pitch squeal coming from the carb. I can only assume it was sucking air in through the crack and that's what was causing it? It's out of dashpot oil (which I'll replace tomorrow) but not entirely sure what the sound was.

 

Would I need to time the engine again as soon I've fitted the kit? New manifold coming in the next few days....

 

Thanks for any advice.

[nicklouse]

Yes you fit the carb and manifold as one.

 

But the carb and manifold might require you to disconnect the top steady so you can make space.

 

you may also find the carb hits the bulkhead if your car was not fitted with that carb originally.

 

yes you will need it set up.

[JamesW83]

Great, thanks - didn't think of that one re: disconnecting the top steady - makes sense.

 

Any thoughts on the high pitched sound coming from the carb area?

[Lplus]

Great, thanks - didn't think of that one re: disconnecting the top steady - makes sense.

 

Any thoughts on the high pitched sound coming from the carb area?

You might have to at least slacken the bolt on any lower steady bars fitted as well.  I tend to fit carbs after fitting the manifold.  A single 11/2 should fit without disconnecting steadies, but not a 13/4

 

Not sure how you managed to snap the corner off a manifold flange (presumably the carb face). 11/2 in or 13/4 in?

 

Also make sure the thickness of the inlet manifold flanges that meet the head are the same thickness as the exhaust manifold flanges otherwise one or the other will not be clamped properly. and may leak.

 

An air  leak due to a crack or leaking gasket might well produce a high pitched whistle.

[JamesW83]

Cheers. I think I just over-tightened the stud going into the manifold, so when I attached the carb and cranked that tight, the stud chewed through the aluminium.

 

Separate question - baseline settings for SU4 carb (swinging needle type)? I've screwed the brass nut all the way up and then slacked 2 half turns, but not sure if this is ok for starting it up again? 

 

Thanks.

[Lplus]

Cheers. I think I just over-tightened the stud going into the manifold, so when I attached the carb and cranked that tight, the stud chewed through the aluminium.

 

Separate question - baseline settings for SU4 carb (swinging needle type)? I've screwed the brass nut all the way up and then slacked 2 half turns, but not sure if this is ok for starting it up again? 

 

Thanks.

Screw the jet nut up until the top of the jet is level with the bridge of the carb body, then screw down 2 full turns.  That's the baseline setting usually quoted in the books.

[JamesW83]

Do I need to adjust the locking nut above it also? Moving the jet nut doesn't seem to be moving the jet up/down.

 

Thanks.

[sonscar]

Try not to loosen the lock nut as it is used when centering the jet tube.Is the choke holding the jet down?Steve..

[JamesW83]

Hope this doesn't sound ridiculous, but even with the adjustment screw fully wound up, the jet was probably 3-4mm off being flush with the bridge. I've used a pair of pliers to bend the armature fractionally, and this has now allowed the jet to sit flush with the bridge. When you say 2 full turns, is one turn a 360 degree turn of the adjustment screw? Appreciate the help.

[JamesW83]

Th

 

Try not to loosen the lock nut as it is used when centering the jet tube.Is the choke holding the jet down?Steve..

Yes, the armature on the choke was holding the jet down. This is the one I've bent to get the jet to sit flush with the bridge.

[Lplus]

Hope this doesn't sound ridiculous, but even with the adjustment screw fully wound up, the jet was probably 3-4mm off being flush with the bridge. I've used a pair of pliers to bend the armature fractionally, and this has now allowed the jet to sit flush with the bridge. When you say 2 full turns, is one turn a 360 degree turn of the adjustment screw? Appreciate the help.

Yes, a full turn is 360 degress or 6 flats of the adjusting nut for an HS4 carb.

[JamesW83]

Stage one kit now fitted and running well - noticeable power increase but running rich (sooty plugs, fuel odour). I've leaned out the jet adjusting screw as far as it'll wind up and it's still too rich. Any ideas what's holding it back? As per above post, I'd bent the link arm to re-set the jet and get it to sit flush with the bridge, so not sure what's in the way. I'm really loathe to remove the carb again, so any in-situ adjustments welcome...

[JamesW83]

Photo attached.

Attached Files

•  IMG_4753.jpg   30.9K   8 downloads

Edited by JamesW83, 01 September 2023 - 09:57 PM.

[mad4classics]

Looks like the jet is not following the adjustment nut.

iirc the ball end of the Waxstat jet link should be underneath and the clip on the other way up.

[Lplus]

Looks like the jet is not following the adjustment nut.

iirc the ball end of the Waxstat jet link should be underneath and the clip on the other way up.

Yep, the ball is below the plate on the HS4 I have. It isn't a waxstat jet.but I don't think it makes a difference.