MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG Midget and Sprite Technical - SU needles

Can anybody give me good starting point for needles for my new engine.
1275 with Twin HS2 Carbs . ITG filter and ram pipes , 3 Branch exhaust , MG Metro cam , standardish head and 1.5 roller rockers. I have no needles as I have built up the carbs and I guess standard needles will probably be too weak.

Thanks
R Mcknight

Assuming you have fixed springs i'd recommend AF needles plus red springs.

I bought some from minispares.com recently. They also stock genuine SU dashpot oil
graeme jackson

Try a pair of AH2, or maybe M and set a little rich at idle till you get to rolling road. Std blue springs.

Hi Graeme, the AF looks very rich for cruising and even more so with red springs, have you tried them on the rolling road?

Peter
Peter Burgess Tuning

Moss do an S.U. chart.
http://www.moss-europe.co.uk/Shop/ViewProducts.aspx?PlateIndexID=18420

There's a handy guide in the Moss catalogue too on page A22. Like Peter, they also suggest AH2 (or AF)though there's not an exact match to your engine specification.
Nick Nakorn

Hi Peter, no, I haven't been on a rolling road yet (and i'll be changing to a 1 3/4 SU soon anyway). I got my spec from the Moss catalogue recommendations -
Bored to 1293, piper 270 cam, larger inlet/exhaust valves, 1.5:1 roller rockers, LCB exhaust manifold and K&N filter.

interestingly, moss don't recommend the 'M' for anything bigger than 1098.

Graeme
graeme jackson

any chance you could post that moss guide?

Im in a simular state with a pair of HS2s from another car, no idea what needles are, seem very rich at top and bottom.

948 bored + 60
standard cam
HS2s
K&N cones
3 to one
12g295 Head
1.3 roller rockers
Compression 9:1
D Paul

Graeme

I have worked with Moss for a long time, they are worried someone may fit needles they recommend and run weak and kill an engine and get sued, hence recommending rich and sometimes very very rich needles.

You also have to remember no one can dyno test everything (if anything)they sell, this means Piper, Kent, K&N etc etc.

You have to remember the fuels and engines are evolving so needles,jets and timing figures change too and ones from books written ages ago will most likely not be correct today.

The threads are as good a place as any as folk can give their own findings.

We go back nearly 30 years of rolling road testing so have a lot of real time testing under our belt.

To cause even more bother and plenty of food for thought....over the last year and a half we are finding the AFRs we have obtained have changed when we retest cars, this goes hand-in-hand with increased ethanol content. Ethanol content is due to increase even more over the next few months.

I attach a graph of a Morgan with TR4 engine running SUs.
It experienced serious misfires and running problems at Classic LeMans. Including excesssive high idle rpms off throttle at the end of the long straights. The engine was running on 102 octane superethanol from the race circuit. It seems this was the cause of the problems.
We tested before and after changing fuel to Shell Nitro +. The Shell made more power everywhere without any octane booster. The engine ran poorly at LeMans as the fuelling was all over the place, even with fettling the AFR the Shell was better as shown in the graph. The problem of the excessive idle rpm was carb freezing, a problem exacerbated with high ethanol content!

Peter


Peter Burgess Tuning

Every time I read comments like Peter's it makes me want to throw up my hands and switch to fuel injection. It seems classic car owners are constantly chasing a moving target to keep their cars working properly with modern fuels. Maybe I should skip the fuel injection and go straight to an electric vehicle conversion. ...rant over.

BTW, I appreciate Peter's input, my rant is against modern progress. I'm now a grumpy old man that just wants those damn kids to stay off my lawn.
Trevor Jessie

Welcome to the grumpy old man club, trevor your white shoes and white belt are in the mail.

I 2nd trevor in thanking peter for his comment on ethanol in fuel.

Trevor and I share the same region of the usa ..Kentucky and missouri so also have same fuel standards ... the rest of the usa has verying degrees, also our fuel stndards change twice a year ... winter and summer, so in actuity, there is probably in.the area of 20 differant types of fuel, so its a hassle for our cars in this ever changing/moving target of fuel standards, im not sure even efi can save the day as im totally convinced that its bad fuel thats killing head gaskets on older engines like my toyota 22re engine in my toy pick up, the engine leans out so badly and the fuel burns so fast the dissy just sits there and looks at me, like, "what are you looking at me for, I didnt shoot liberty valance" ...haha
But yes ... fuel is getting to be a real.issue on everything and everywhere.

Luckly ive still got one pump in town that sells non ethanol 95 octane...and god what an amazing stuff that is... and a matching price tag
Prop and the Blackhole Midget

Just some insight

In danial stapletons book, which mine is for sale for only $8300.00 he does have a dedicated chapter for reprofiling SU carb needles for those that are unfortant to not be able to use a rolling road,

That said, id do the rolling road esp from peter burguss before id reprofile 2 matching needles, but as a last resort, danials method looks like a fun saterday afternoon if your into that kind of thing

prop
Prop and the Blackhole Midget

Paul D
I am running a spec not far from yours 567 cam, 9.5Cr, but std rockers. HS2s with V3 needles and blue springs.
Alan
Alan Anstead

This thread was discussed between 15/08/2014 and 18/08/2014

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.