HS4 carb needle

[MorrisJohn]

I’m going to be fitting an HS4 to my standard Marina 1275cc engine, along with matching Marina manifold, exhaust and a K&N cone filter. Essentially everything standard Marina, except for the filter.

The carb is a refurb unit with needle AAQ, but this I presume is intended for use with a standard air filter and the K&N will weaken the mixture?

I realise needles and tuning are a bit of an art form, but what might be the best starting point needle wise for this set up?

[philthehill]

I would suggest a good start would be to quote the number on the carb tag.
For example a AAQ needle is fitted to a AUD354 HS4 SU carb as fitted to a 1275cc Morris Marina circa 1971 - 1972..
Once the carb number is known a qualified opinion can be given.

[MorrisJohn]

I would suggest a good start would be to quote the number on the carb tag.
For example a AAQ needle is fitted to a AUD354 HS4 SU carb as fitted to a 1275cc Morris Marina circa 1971 - 1972..
Once the carb number is known a qualified opinion can be given.

Thanks. I believe the HS4 is FZX1189, which I further believe was fitted between 1976-80 to 1275cc units?

[philthehill]

Thank you for the updated information.
For a start I would use the standard needle ADG as specified in the link below
https://sucarb.co.uk/carbspec/carburett ... s/id/1963/

[MorrisJohn]

Thank you Phil

[MorrisJohn]

Might I ask in relation to these upgrades, would there be a benefit of fitting an LCB outlet manifold and one of the water heated mini inlet manifolds instead of using the standard Marina manifold that I have?

As above, I don’t want to create a rocket ship. Just give it a little bit more poke.

In terms of cost versus benefit what are your opinions on LCB versus the standard Marina manifold?

One obvious benefit I can think of is elimination of the dreaded exhaust down pipe connection.

I have a loan copy of Vizard’s Tuning the A-Series engine that I’ll read the relevant chapters of. Admittedly though, some of it is over my head.

[philthehill]

If you do not want a 'rocket ship' there is nothing wrong in using the Marina cast manifold assembly. It would be my first choice as to manifolds and would have preference over a LCB and separate alloy inlet manifold.
With the above I would use the ESM marina to minor front pipe.
https://www.morrisminorspares.com/engin ... ss-p830058
The Vizard book can be a bit of a headache when trying to understand his processes. Some of the Car and Car Conversion tuning books are much easier to understand.
https://www.ebay.co.uk/itm/314381574552 ... R_7z2v7HYQ
There is also a Car and Car Conversions book in the same series relating to the MG Midget/Sprite which again is much easier to read.

[MorrisJohn]

That’s very helpful indeed Phil, thank you. Decision made. I shall go with your recommendation and use the standard Marina manifold. I will also fit the Marina to Minor front pipe.

I’ll keep an eye out for one of those books too

Much obliged.

[MorrisJohn]

Thank you for the updated information.
For a start I would use the standard needle ADG as specified in the link below
https://sucarb.co.uk/carbspec/carburett ... s/id/1963/

Phil, is the needle in that link what would be known as a “top hat” needle?

[philthehill]

Top hat needles are usually to be found in carbs with biased needles. I am not sure that the needle in your carb is biased.
To identify if you have a biased needle or not is the the needle is loose fitted in the piston?

[MorrisJohn]

Thanks Phil. I’ve decided to save hours of faff and guess work by getting an SU carb tuner from the mini scene to set it up for me, profile the needle etc.