Thread: jet size for 101 carby

Originally Posted by iain reed

hi all
just to put it out there , need to up the size the jets for my old 101 as to convert 3.5 to a 4.6 litre what jet size do i need ???
thanks in advance

You cannot put a question out there like that and then add that you are going to a 4.6.

Didn't you dispose of a 4.6 to another well known 101 owner who is just letting it sit in his shed doing nothing?? So have you acquired another 4.6?? or building something up?? Where did you get it??

What are your plans???

Garry

He has been holding out on us.

So he had 2x4.6s

There are many paths to the top of the mountain!

Originally Posted by iain reed

hi all
just to put it out there , need to up the size the jets for my old 101 as to convert 3.5 to a 4.6 litre what jet size do i need ???
thanks in advance

not that simple. i think bigger carbs would be the go but manifolds are the limiting factor here so forget that.

you could do your self a favor and fit a couple of O sensors, if not its going to be old school.
i would say best to work with the needles and not the jets themselves.

do you know how to balance your carbs and all the normal tuning of SUs?

thanks
never holding out on you guys, did not want to report it as it still a work in progress, so needles are the way to go ? mmm will look into it any advice for the carbys going to leave old manifold on as i dont want muck around with the chassie , yes ron i do carry the old gear circilp plyers etc with me,

OK
This is where I would start with the problem.
Find some spare 3.5 CD stromberg carbys which should be easy.
Use the spare carbys as the ones you change and leave the ones which worked on the original 3.5 alone as a reference point.
I would get ahold of some number drills and slightly enlarge the size of the exsisting main jets.
The main jet size is your top end power and the needle does every thing else.
Get the needle and place it in a drill chuck and spin it .
Whisle spinning it hold some sand paper on it to make the needle slightly thinner.
The end of the needles point is 3/4 throttle mixture.
the top end of the needles shaft is idle though to 1/3 throttle mixture .
The needle can also be adjusted for mixture 1/2 to 3/4 throttle by moving it in its adjustable hole in the diaphram body( three positions ?)
In the old days I could set up a english motor bike carby by ear and looking at the exhaust pipe for colour and playing with the needle and jet.
This is much , much harder today is there is no lead in the exhaust and the exhaust pipe will not change colour much with fuel mixture.
I would be getting a hold of a air/fuel ratio mixture sensor either hand held or in built in the vehicle(wide band O2 sensor) and that will give you a idea of how the vehicle is burning the fuel.
Note 101s standard 3.5 carbys were set up from factory very rich for maximum pulling power and to run on MT army fuel and the jetting was different to the range rover motor.
Setting up the carbys will be trial by error and you need some gear to do it with experience.
Doing it on a 4wd dyno saves time with a A/F ratio sensor but could still be done by road driving it .
Ron

Iain - pre fuel injected 4.2 six cylinder jags had the same CD carbs - engine is just a bit smaller than the 4.6 but power will be similar or better so needles etc would be similar to what you need. If you research what settings they had might be suitable.

Likewise - the early 3.5 V8 101s had SU carbs which some say are a bit better than the CD carbs. Again a set off a early 4.2 six cylinder jag engine could be an option.

Garry