reece fish carbs, amal, su

[vmaxscart]

Reece fish carbs , all the old stories say they are great , work wonders etc , anyone in this era used one ?
I've tried 2 , (see vmaxscart on youtube) they always give very rich mixtures when set up according to the instructions . I have a rolling road with wideband gas sensor so its easy to see whether anything really works .
I tried adjusting them to give the correct mixture and have to say disagree with all of the old school assumptions in that it atomises the fuel better than an su , i fact looking down the carb when opening the throttle it just chucks about a tablespoon full (nice metric measurement ) down the barrel completely un atomised !.
I'm trying an amal concentric now which does seem to run better at idle at least to 1 perc co just waiting for some spare time to get it back on the rollers !

1963 850 super deluxe

[mk1]

Stuart,

I tried a 1.5 inch Reece fish years ago on a moderately tuned 1071 & found very similar results to you.

It always seemed to lack adjustment. Right(ish) at tick over, meant lean at high revs & right at high revs meant spectacularly rich at tick over.

I suspect that Clive Trickey's advocacy of these carbs may have had more to do with money changing hands than actual performance improvements.

Mark F

[ivor badger]

They seemed to work on Mini7 racing, being the carb of choice at one time. So maybe they work well at full throttle. i'll see if I can have a word with someone who used to work with them in the 60s.

knew someone who had a pair on a Mini Marcos for sprinting and he seemed to spend the whole day adjusting the carbs between runs.

[Frogeye61]

I was under the assumption they were variable for the whole range, but that sounds too simple. And as a single carb they should work well, NEVER use a double. This much comes from the good book. And no I've never used one.

However in the old days they wanted a good rich mixture. Richer meant more power, but not too much. On the dyno we achieved best power at lambda 0.85, which means air fuel ratio around 12.5:1. If the fish could hold something around this - and it really didn't matter how close - it would work fantastic.

But it won't continuously hold lambda 1 (14.67 a/f) which is critical for catalysts. Therefore engine management systems for the newer cars.

[vmaxscart]

Yep that seems to ring true , although i tried two carbs it was just to check I didn't have a bad one , haven't tried as twins . It can hold full throttle mixture at 12.5 afr good for racing although I still worry about the full 'dump' throttle enrichment . For road use I need control of idle , cruise and mid range . The Amal carb does seem to achieve most of this , it needs much lower fuel pressure at 1.5 psi and its a bit of a pain setting up with upper and lower jets , needle and air bleed screw .
Reinforces how good the old Su is !
It ran 55 bhp with twin 1 1/8 in su's
52 bhp with single 1 1/4 reece
The Amal is 34 mm no figures yet
10:1 comp , 12g202 modified head , 1960's small bore 3 into 1 with 1 1/2 exhaust (od)

[mk1]

I look forward to seeing the Amal figures particularly.

[dazibee]

I have just looked in Trickeys yellow book. He describes how to adjust the cruise air fuel mixture of a Fish carb by adjusting the radial position on the spindle of the throttle butterfly to prevent the mixture being too rich at part throttle

[vmaxscart]

Yes I ran through many adjustments with the fish carb correct mixture at light load meant too rich at idle , moving the butterly disc is an art , moving it such small amounts i could not feel but saw Changes to the mixture on the rolling road .I did drill out the air bleed holes from 2 mm to 4 mm giving more bleed at tick over thus reducing airflow over the butterfly . This did make a better idle mixture but then too lean at light load .
Friday was spent on the rollers trying to get the amal to work , again like the fish 2 out of 3 was achievable idle/ cruise/ full load but not all three.
I was trying to find the best period car setup with this , what I didn't realise earlier is that the hs4 carb was manufactured from 1958 with pre wax stat jet , while I had been looking for a h4 to try .
Today I fitted the hs4 after rebuilding checking etc etc , really it's amazing . I have throttle response ,no flat spots 14 :1 at cruise , 12.4 at load and it's like a different engine , really had me thinking today how good it is for a 850 ! 58 bhp @ 5000 rpm and 45 ft lbs at 4000 , comparing to twin 1 1/8 at 55/33 respectively . Also hydrocarbons down to 350 at idle , twins 800, Amal 1300, Reece 2000!
Single su why did I ever doubt it

[mk1]

Single su why did I ever doubt it.

Couldn't agree more, but for most people the look is as (if not more) important than the performance