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 Post subject: Mixture question
PostPosted: Mon Aug 02, 2021 9:26 am 
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998cc
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Joined: Fri May 03, 2019 7:17 am
Posts: 519
1275 engine and No 1 & 4 always burn leaner than 2 & 3 which is a quirk of the A series.
Question is I assume it is better to have 1 & 4 correct with 2 & 3 somewhat rich rather than running the outer 2 cylinders lean?

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 Post subject: Re: Mixture question
PostPosted: Mon Aug 02, 2021 8:19 pm 
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Oh dear, worry, worry...

Joined: Fri Jun 19, 2009 5:31 pm
Posts: 686
Location: North Rocks
Hi Steam
If your mixtures are correct it's not really a problem, but if your are worried about it you can run one heat range colder on 2 and 3 as BMC did back in the day :) in competition, some times they run higher compression in 2 and 3 (one point higher)
Graham Russell

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 Post subject: Re: Mixture question
PostPosted: Thu Aug 05, 2021 10:19 am 
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Joined: Mon Mar 09, 2020 8:06 pm
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Location: California, USA
What air-fuel ratios (using a wide-band O2 sensor to tune) are normally used at cruise and full load?

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- 1968 Australian Mk1 Morris Mini (originally a MiniMatic but a previous owner converted it to a 1275 and rod change box)
- 1964 Lotus 23B


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 Post subject: Re: Mixture question
PostPosted: Thu Aug 05, 2021 8:18 pm 
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Oh dear, worry, worry...

Joined: Fri Jun 19, 2009 5:31 pm
Posts: 686
Location: North Rocks
HI Murty
With the SU caries 14 to 15 on cruise full load 13.5 to 14
With webers 13 to 14 on cruise full load 12.5 to 13
Graham Russell

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"It's better to be not informed than ill-informed"


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 Post subject: Re: Mixture question
PostPosted: Thu Aug 05, 2021 11:54 pm 
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Joined: Mon Mar 09, 2020 8:06 pm
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Location: California, USA
Thanks Graham

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- 1968 Australian Mk1 Morris Mini (originally a MiniMatic but a previous owner converted it to a 1275 and rod change box)
- 1964 Lotus 23B


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 Post subject: Re: Mixture question
PostPosted: Fri Aug 06, 2021 9:38 am 
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998cc
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Joined: Fri May 03, 2019 7:17 am
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GR wrote:
Hi Steam
If your mixtures are correct it's not really a problem, but if your are worried about it you can run one heat range colder on 2 and 3 as BMC did back in the day :) in competition, some times they run higher compression in 2 and 3 (one point higher)
Graham Russell


Thank you Graham, excellent advice as usual.
It is not worrying me enough to change the inner plugs, i will keep 1 & 4 Correct with 2 & 3 slightly richer. All good.

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