What Needles?
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What Needles?
I run a 3.5 V8 with ported and polished heads, a race cam and omega pistons......the rules for my sport allow me to use uprated needles from standard......any suggestions which needles would be a good replacement to get top performance??
Hello Jamie,
If for argument sake you are running twin SU carburettors, being a non standard setup, none of the needles available will be perfect from idle to red line, although some will be closer than others.
You may find some will be spot on through the low and mid range, but too lean at the top end, while others may be too rich at the top end. Some may be lean in spots and too rich in others.
Polishing needles and using a using diagnostic equipment to measure air / fuel ratio at all points in the rev range, running on a rolling road is the perfect way to go.
Ron.
If for argument sake you are running twin SU carburettors, being a non standard setup, none of the needles available will be perfect from idle to red line, although some will be closer than others.
You may find some will be spot on through the low and mid range, but too lean at the top end, while others may be too rich at the top end. Some may be lean in spots and too rich in others.
Polishing needles and using a using diagnostic equipment to measure air / fuel ratio at all points in the rev range, running on a rolling road is the perfect way to go.
Ron.
4.6 Rover 3500 P6B
Sorry yes they are SU's. The only equipment i have at the moment is airflow meters to go over the trumpets. I race on 400-500 metre ovals so i'm after the better response coming out the corners at low revs (2000ish rpm), although obviously a good pull down the straight is important too. Thanks for any advice received.
Hello Jamie,
The idle mixture which is largely governed by the first two measuring points on the SU needles are virutally the same for all needles that would be fitted to a Rover V8.
So, best to buy a batch of different needles and do some testing.
BAK is a good needle to start with, but if that proves to be too lean, then in order of increasing richness....BAF and BBW.
Any signs of hesitation while accelerating, stop and swap in the next richer pair oif needles.
Reading the spark plugs can be a good indicator, as will the colour of the exhaust pipe interior. Dark grey with a brownish hue will show that you are pretty well "right on the money".
Best of luck and do lets know how you get on.
Ron.
The idle mixture which is largely governed by the first two measuring points on the SU needles are virutally the same for all needles that would be fitted to a Rover V8.
So, best to buy a batch of different needles and do some testing.
BAK is a good needle to start with, but if that proves to be too lean, then in order of increasing richness....BAF and BBW.
Any signs of hesitation while accelerating, stop and swap in the next richer pair oif needles.
Reading the spark plugs can be a good indicator, as will the colour of the exhaust pipe interior. Dark grey with a brownish hue will show that you are pretty well "right on the money".
Best of luck and do lets know how you get on.
Ron.
4.6 Rover 3500 P6B
I'm busy planning my re-build project and will need to do a similar needle hunt, is there a way of narrowing things down to "likely" suspects?
My project will be a 4.6 on 3.5 heads under standard Landrover v8 SUs.
I found and have been looking at winSU, however, not having run the engine in the vehicle on a rolling road I dont know what it's doing. Is the best plan to find out what the existing needles do to my mixture raio either rolling road or rig up and oxy sensor and drive it about? Then begin the hunt with winSU?
My project will be a 4.6 on 3.5 heads under standard Landrover v8 SUs.
I found and have been looking at winSU, however, not having run the engine in the vehicle on a rolling road I dont know what it's doing. Is the best plan to find out what the existing needles do to my mixture raio either rolling road or rig up and oxy sensor and drive it about? Then begin the hunt with winSU?
Simon.
4.6 on SUs in 110CSW
4.6 on SUs in 110CSW
hi
there are several threads on 4.6 engines on SUs, a search on this section would save you alot of time and gain you more responces but in summery.
The inch 1 and 3/4 is a bit small for the 4.6 engine, to use a pair you need to first select the right spring so the piston on the 1 3/4 does not top out at too lower revs, when selected however you will be have too much air velocity through the carb and it will be difficult to select the right needle and jet selection and the carb will tend to run rich (and be very sensative to needle selection).
A better solution is to start by fitting a pair of 2" SUs off the jag and open out the manifold to match, then select a spring so the piston on the carb reaches the top at about 500 revs below max, then select jets (both the jet with the needle and the jet at the base of the jet feed tube) to get the mixture right fo this bit of the rev range richening slightly as you reach max revs. Finally select a needle for the jet that will control the mixture to what you want as the revs rise.
Personally for a 4.6 I would go EFI and aftermarket ECU as by the time you have done all the above set up for the SUs on a rolling road you will have spent more than you would have on an EFI set up.
Mike
there are several threads on 4.6 engines on SUs, a search on this section would save you alot of time and gain you more responces but in summery.
The inch 1 and 3/4 is a bit small for the 4.6 engine, to use a pair you need to first select the right spring so the piston on the 1 3/4 does not top out at too lower revs, when selected however you will be have too much air velocity through the carb and it will be difficult to select the right needle and jet selection and the carb will tend to run rich (and be very sensative to needle selection).
A better solution is to start by fitting a pair of 2" SUs off the jag and open out the manifold to match, then select a spring so the piston on the carb reaches the top at about 500 revs below max, then select jets (both the jet with the needle and the jet at the base of the jet feed tube) to get the mixture right fo this bit of the rev range richening slightly as you reach max revs. Finally select a needle for the jet that will control the mixture to what you want as the revs rise.
Personally for a 4.6 I would go EFI and aftermarket ECU as by the time you have done all the above set up for the SUs on a rolling road you will have spent more than you would have on an EFI set up.
Mike
poppet valves rule!
