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SU Needle Selection

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SU Needle Selection
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  This topic is about my 1970 MG MGB
benhutcherson Avatar
benhutcherson Gold Member Ben Hutcherson
Louisville/Frankfort, Kentucky, USA   USA
1970 MG MGB
I need to order replacement needles for my HS4s, and since it's mostly Greek to me I was wondering if I can get some suggestions:

18GH engine with 2923 head for ~9.4:1 C/R
Stock cam(for now)
Ported vacuum
Generally run 89 octane gas
"Cooper Cans" with stock type Wix paper filters



Edited 1 time(s). Last edit at 2017-12-06 03:08 PM by benhutcherson.

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tvrgeek Avatar
tvrgeek Silver Member Scott S
Hillsborough, North Carolinia, USA   USA
1965 MG MGB
STOCK needled, as specified. I was looking for one slightly leaner inidle, but they don;t have one and learned, MGs don't like slightly leaner idle.

Do buy them from SU. I have had issues with non genuine SU parts like the jet coming apart.

http://sucarb.co.uk/cf/vehicle/list/?manufacturer=MG&vehicle=M.G.B



Cogito ergo sum periculoso

ClayJ Avatar
ClayJ Silver Member Clay Johnston
Mt. Olive, MS, USA   USA
1972 MG MGB
What is leading you to think new needles are needed?

I normally contact Joe Curto for SU advice and parts.

I assume these are later HS4s with biased (spring loaded) needles?

The number of the metal tab under one of the float bowl lid screws would help.

New jets might also be in order if you think new needles are needed.

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ClayJ Avatar
ClayJ Silver Member Clay Johnston
Mt. Olive, MS, USA   USA
1972 MG MGB
Also, here is a reference for stock parts by year:
http://teglerizer.com/mgstuff/SUcarbs.htm

tvrgeek Avatar
tvrgeek Silver Member Scott S
Hillsborough, North Carolinia, USA   USA
1965 MG MGB
AUD is actually the answer. Buy from Joe or direct from SU. Buy the real SU rebuild kit. Yea, it costs three times as much but is worth every bit.



Cogito ergo sum periculoso

riley1489 Avatar
riley1489 Gold Member Bruce H
Great White North, QC, Canada   CAN
1953 Jaguar XK120
1959 Riley 1.5 "King George"
1973 MG MGB
In reply to # 3640958 by benhutcherson I need to order replacement needles for my HS4s, and since it's mostly Greek to me I was wondering if I can get some suggestions:

Ben,
Nothing special about your engine so I suggest install the standard metering needle, AAE.

Why do you "need replacement needles "? are they damaged?

B



Check your ego Amigo!

Basil Adams Avatar
About 12 miles from Sears Point, CA, USA   USA
Ben, If you have the stock, solid needle (not the spring loaded ones, a standard #5 needle will do. I have them in stock. You don't need to buy the whole rebuild kit to get a new needle. Thanks. Basil 707.762.0974 basiladams@yahoo.com



Basil C. Adams
1956 MGA Coupe (Show Car)
1957 MGA Roadster (Driver)
1958 MGA Coupe (Racecar)
1959 MGA Coupe (unrestored)
1960 MGA Coupe (unrestored)
1960 MGA Roadster (Driver)
MKIII Elva Courier (E1056)
1967 427 Cobra
1972 Alfa Romeo Montreal
A coupla late MGBs
1960 Austin Healy BN7
More Cars than Brains

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Donthuis Avatar
Donthuis Don van Riet
Rijswijk, ZH, Netherlands   NLD
IF your 1970 B has a lot of mileage behind it after 48 years, you could renew both needles and jets. Fluid passing past both, wears the material VERY slowly away. This means the needle position must used will get the wear to this position in the jet too, meaning idle rpm setting and higher carb "stations" are no longer as they should be. New needles are tapered in alignment with as yet non-used jets

I renewed the jets in my HIF's once only, after about 40 years of usage, PO period included..... eye rolling smiley

Speedracer Avatar
Speedracer Platinum Member Hap Waldrop
Greenville, SC, USA   USA
1967 MG MGB Racecar "The Biscuit"
In reply to # 3641253 by Basil Adams Ben, If you have the stock, solid needle (not the spring loaded ones, a standard #5 needle will do. I have them in stock. You don't need to buy the whole rebuild kit to get a new needle. Thanks. Basil 707.762.0974 basiladams@yahoo.com

I'll add this, if any of you have bias needle carbs and want convert to fixed needles, Joe Curto sells a very simple and inexpensive solution, it is a brass bushing go into bias needle carb's piston that allows you to use a fixed needle, like Basil speaks of. Another tip for you that know these carbs, early fixed needle carbs have jet bearing that when viewed from the bridge have a gap around the hole in the bridge, hence the reason for jet alignment. Jet alignment in early HS carbs can be a real SOB, to put lightly, trying to get that jet bearing perfectly aligned so you get a good clean drop on the carb piston. However later biased needle carbs use a different jet bearing the fit the hole in the bridge snug, hence no alignment. well if use one of these later jet bearing in combination with a fixed needle you will perfect jet/needle alignment with out all the hassle, I have been doing for years on race prepped HS carbs. Als FWIW, all jet bearings in all size of HS carbs interchange.

There again the factory did not create biased needles because they were better, just easier to deal with. On stock probably doesn't matter much one way, or the other, on a performance car, it is for sure better with solid needles.



Hap Waldrop
Acme Speed Shop
864-370-3000
Website: www.acmespeedshop.com
hapwaldrop@acmespeedshop.com


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benhutcherson Avatar
benhutcherson Gold Member Ben Hutcherson
Louisville/Frankfort, Kentucky, USA   USA
1970 MG MGB
Thanks everyone.

I wasn't sure if stock would still be correct with a higher-tha-stock C/R, but it sounds like that doesn't make a difference.

As to why replace them-I guess that's what I get for only giving what I thought was pertinent information. Primarily, I actually am replacing the jets due to wear(I can see under magnification that both have ovalized a bit), plastic tubes in questionable condition, and some other issues that hamper the operation of the car. It was my understanding that, with a biased needle at least, the needle and jet should be replaced as a pair.

I've never dealt with fixed needles. I like the "don't worry about it" part of the biased needles, but I know inuitively that a fixed needle should be better in every way. I know that fixed takes a bit more work to set up and that I likely won't see any benefit, but I'll go ahead and take the time to change them.

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