Is it normal to smell petrol when you open the bonnet?
I have looked for leaks but everything looks OK. Is this normal with SU’s?

 

i've found to be pretty much the case on any car with SU carbs, as the floatbowls are open to the atmosphere through their overflow tubes. only when it pervades the interior, do i get concerned.

the common use of electronic fuel injection on more modern cars has practically done away with it altogether.

 

Thanks. No smell inside the car.

 

My experience is that SUs produce little or no petrol smell compared with Dell'Orto or Weber. Of course, some fuel vapour will escape from any carburettor that is open to the atmosphere unlike modern injection systems that are completely closed. It's all relative.

 

If you have a small of petrol under the bonnet it is fairly normal for all the reasons above but an excess smell can mean a vapour leak from the SUs. A common place for the SU to leak fuel is from just below the front carb where there is a bridge between the carb and the AED (choke). At the bottom of the bridge a re two brass banjo bolts one large one smaller. These can come loose with the vibration of the engine and fuel can leak out. It might not be a dripping leak but you will smell it. To check if yours are leaking the best method I have found is to get some blue paper towel and lie this under the carbs first of all. Fairly close to see if there are any drips of fuel. The light blue paper turns dark blue when it comes in contact with the fuel. If there are no signs of a drip on to the paper try wiping the bottom of the carbs around the bridging piece. If you locate an area where the paper is getting wet and going dark blue you will find your leak. The banjo bolts on the base of the bridging section are very difficult to get to and they are an odd Whitworth size so finding a suitable spanner to fit is also a challenge but cinch these bolts up a fraction and it should clear any leaking of vapour. Do not over tighten as they are a brass bolt in an aluminium housing. If cinching the bolts up does not work then you need to replace the Fibre and Aluminium washers numbered 42, 44, 46 and 47 in the diagram. Part numbers listed below. To do this is means the carbs need to be removed.

The bridging piece is 41 in this diagram and the Banjo bolts are 42 and 45.



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Thanks. I will take a look this weekend

 

in my experience it is usually the AED (Auxiliary Enrichment Device) that leaks.
One tiny drop leak causes an enormous fuel odor.

Another possible leak is at the Glass Bowl Fuel Filter, which has IN / OUT banjo fittings.

The size of the banjo Bolts is a pain to figure out so I have used the small adjustable wrench from the Tool Kit.

 

i'd have to double check, but IIRC boltheads may be whitworth. at least its the first thing i check when working on my old british cars. ...makes sense that a "tool kit" type wrench would fit. as they would supply a whitworth wrench if necessary.