Kunena :: Topic: Choice of needles for H4 Carb in 1800 MGB 3-main (1/1)

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TOPIC: Choice of needles for H4 Carb in 1800 MGB 3-main

Choice of needles for H4 Carb in 1800 MGB 3-main 11 years 2 months ago #21

clacksman OFFLINE Expert Boarder Posts: 82 Thank you received: 8 Karma: 0	Right, so you have the No.5 needles. These hardly differ from my MBs, except between stations 3 to 7 where mine are actually marginally leaner. Really not much difference. Very interesting. Thanks Günter Regards, Andy
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Choice of needles for H4 Carb in 1800 MGB 3-main 11 years 2 months ago #20

admin	Andy, no I mean standard needles for early MGB. I have the 3 brg engine as it was a direct swap (nearly) Günter
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Choice of needles for H4 Carb in 1800 MGB 3-main 11 years 2 months ago #19

clacksman
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Hi Günter,

I take it you mean standard needles for the ZB(EQ)rather than standard for MGB (5). If so, then I am running much richer than you at wider throttle with my MB needles. I am surprised you can use the EQs - but perhaps I should try them!

My car is much quieter since I fitted the 5-speed box. I was already using the 4.3:1 diff before I changed the gearbox and that seemed an ideal combination with the old 1489 engine. Now that I have fitted the 1800 engine I think a 3.9:1 diff would be even better, so I have acquired one. However, if I fit it now, the speedo will be wrong again and I have only just succeeded in getting it properly calibrated. I had to send the speedo to Richfield twice before they got it right!

Andy

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Choice of needles for H4 Carb in 1800 MGB 3-main 11 years 2 months ago #18

admin	Hi Andy, I have nearly the same modifications you use, except the gearbox. I use standard needles in my carbs and I'm happy with it. 80mph is quite fast, isn't it? I wonder what you have done against the noise? I think my car gets too noisy after 70 or 75 mls. Günter
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Choice of needles for H4 Carb in 1800 MGB 3-main 11 years 2 months ago #17

clacksman
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I am using H4 carbs on my 1800 MGB engine. I am also using Trevor Jones' Derrington style exhaust header with 47mm pipe, Ford T9 5-speed gearbox and currently, an MGA 4.3:1 diff. I may change this for a 3.9:1 at some stage.

After some on-line research I have used MB needles which give plenty of acceleration right up to 80+. My Gunson Colourtune tells me the mixture is OK at tickover and moderate throttle but I suspect that it is too rich at wider throttle.

I know that the only reliable method is to use a rolling road dynamometer and compare needles but this is expensive and probably not justifiable for my type of driving. So I thought I would ask what needles other Magnette owners with similar setups are using.

I would be interested to hear from any Magnette owner who is using an H4 carb with the MGB 1800 engine whether or not they have the other mods that I am using.

Regards,

Andy