Carburettor AUC 888

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MoggyMatilda
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Carburettor AUC 888

Post by MoggyMatilda »

1958 Morris Minor 948cc with AUC 888 Carb.

948cc with an upgraded cylinder head polished & ported. Car has been running rich & running through petrol at a serious rate. Tried to adjust it but the plugs still soot up. Is this carb up to the task with an upgraded head or should I put a larger carb on?

I tried the carb off my sisters 1098 traveller & the car wouldn’t run at all. Don’t know what I’m doing wrong. PLEASE HELP!
philthehill
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Re: Carburettor AUC 888

Post by philthehill »

Here is the spec for a standard AUC888 fitted to a standard head.
http://sucarb.co.uk/carbspec/carburetto ... s/id/1904/
Check against the link above as to what main needle and jet is fitted to the carb.
The H2 1 1/4" carb will deliver the same basic requirements as the later HS2 1 1/4" carb. In some ways the H2 carb is better than the HS2 carb.
Check the float needle for serviceability and check the fuel level in the float chamber. Search the SU link above for fuel level details - http://sucarb.co.uk/technical-h-type-ca ... -servicing.
What head is fitted to the engine? The casting number which identifies the head is cast into the head just underneath the the rocker shaft.
Can you also please enlarge on what has been done to the head?
Once the head details are known then we maybe able to advise the next move.
Last edited by philthehill on Wed May 11, 2022 3:40 pm, edited 2 times in total.

JOWETTJAVELIN
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Re: Carburettor AUC 888

Post by JOWETTJAVELIN »

Just out of interest, what cylinder head is fitted?
philthehill
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Re: Carburettor AUC 888

Post by philthehill »


MoggyMatilda
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Re: Carburettor AUC 888

Post by MoggyMatilda »

The cylinder head fitted is as follows

12g202 cylinder head
Fully reconditioned
Unleaded seats
Double springs
Skimmed 40 thou
Raised compression from 9.8-10.1

This was recommended to my by MCCS Engineering as they build beautiful A series engines. The same head is used in their 948cc sport package engines. Fantastic work & I’m super happy with the cylinder head itself.

I will cross reference my carb with the link provided & see if the needle etc matches. I’d like to keep the H2 carb if I can get the engine running right.

Also could someone explain to me the reasoning behind weak,standard & rich needles? I’d take a guess that the clue is in the name, but further explaining on why one would need to use either of said needles.
philthehill
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Re: Carburettor AUC 888

Post by philthehill »

As you have a non standard head the needles in the link can only be considered as a start line. You will have to experiment with the needles.
The amount of fuel allowed to pass through the main jet is controlled by the needle so the amount of fuel allowed to pass is in the name:
Weak needle - less fuel flow than the standard needle. Standard needle - normal fuel flow. Rich needle - larger flow than the standard needle.
I would be tempted to try a AN needle which is the standard needle for use with a 1098cc 12G202 head. An alternative is a EB needle which is weaker (gives less flow) than the standard AN needle.
Last edited by philthehill on Sun May 15, 2022 2:22 pm, edited 1 time in total.

MoggyMatilda
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Re: Carburettor AUC 888

Post by MoggyMatilda »

Ok thanks for the help.

I guess it will take some trial & error to get it right as you say I’m not running a standard 948 head.
MoggyMatilda
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Re: Carburettor AUC 888

Post by MoggyMatilda »

Just another question. When they say H2 “paper filter” what do they mean by that? Is there a filter in the carb? Or are they referring to the air filter?
philthehill
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Re: Carburettor AUC 888

Post by philthehill »

They are referring to the air cleaner paper filter.
There is no filter in the carb.

MoggyMatilda
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Re: Carburettor AUC 888

Post by MoggyMatilda »

Ok thanks. I’m pretty new to Morris minors so I’m learning as I go.

I’ve noticed there’s no overflow in the float chamber on my H2, should there be?
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oliver90owner
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Re: Carburettor AUC 888

Post by oliver90owner »

Much better to send excess fuel through the engine and out the tailpipe than leaking in the engine bay. Firstly, safety - and secondly, the rough running should be noticed by the user.
jaekl
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Re: Carburettor AUC 888

Post by jaekl »

The bowl needs to be vented to work properly. Without a vent it can build up pressure which will prevent the valve to close and the fuel will be flow out of the jet in the carb due to the pressure. There is a small vent hole. I don't recall at the moment but it is probably under the formed washer under the top mounting bolt.
philthehill
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Re: Carburettor AUC 888

Post by philthehill »

There are two notches cast into the top of the lid either side of the central hole to the float chamber so allowing the float chamber to vent to atmosphere.
The two notches are under and covered by the top fastening. See link below:-
http://sucarb.co.uk/float-chambers-spar ... t-lid.html
This is the type of float chamber type fitted to the OPs carb:-
http://sucarb.co.uk/float-chambers-spar ... embly.html
See part list link for details:-
http://sucarb.co.uk/carbspec/carburetto ... s/id/1904/
Some H2 carbs have the vent pipe for the float chamber and some do not. Some just have the vent washer or notches.
I would check to see if the float chamber has the two vent notches. If not it is easy to file a couple of vent notches into the top.

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