When they removing the lead from petrol it made plug colours pretty irrelevant...

As mentioned earlier, outside plugs always look leaner than the inside ones ..because of the port design.

Compare 1 with 4 and 2 with 3....

Could be bit more oil in 2 ...but what does 3 look like?

The thread on 2 looks a bit scungy ..but that's not a tuning issue...

And SUs are variable venturi carbs so size doesn't reeally matter (within reason). The carb flows as much air as is needed. The main problem is that the needle works over a different range ..

Just get some new plugs... 4 years use out of a set seems quite reasonable. 60/70 BMW engines were much more finicky..

Cheers, Ian

G'day Ian,

Plugs 1 & 4 look much the same as each other as do 2 & 3 - 3 looks pretty much the same as 2. I cleaned up the threads in the head best I could with a pointy screwdriver thing to clear out any carbon in the threads and then with a rag soaked in kero. New plugs screwed in easier and by changing them more often, there shouldn't be as much carbon build up on the end of the threads.

The bloke who did the initial tune said it was overfuelled slightly so maybe that's why 2 & 3 have the carbon buildup if more fuel is going into those 2?

Cheers, Rocky

Is the guy who tuned it actually familiar with SU carbs?

That will help us determine what's really happening and what "over fuelled" may have actually meant.

_________________
1986 Mayfair (998 auto), 1974 S, 1974 Van, 1972 PMG Van

Too many minis

Yeah he only works on English cars and there were a heap of Minis, Austin Healeys and a few MGs in his workshop. He reckons the carby was set up ok but from the way he explaind it (or as least I understood it ) I probably could have just used a HS2 instead of the HS4. When I got the car, it had twin HS2's on it but they weren't a matched pair and were bolted to what looks like a homemade inlet manifold

I had the carby fully rebuilt over in Adelaide (not Minisport) and he asked what motor it was going on. I told him it's an standard 850 (40thou oversize and a set of extractors) and he reckons he'd set it up to suit.

Cheers Rocky

Rocky, from the look of plugs 1 and 2 I'd say your tuner not spinning stories.

There's and old saying "how fa$$t do you want to go?". You can spend big bucks getting it "right" but I strongly doubt you'd notice any difference. Both the SA carb supplier and your local (?) tuner came to the same conclusion so it looks like you'r setup is pretty much in the ballpark. The "overfuelled" comment suggests to me that the tuner may have thought a different needle might be justified but thought the effort not worth chasing...

Twin SUs can work better than a single but it really depends on how good the manifold is. A twin manifold (even home made - and expensive ones can be made of welded steel tubing so can look pretty basic) should flow better as it has less bends so can even out the flow between cylinders.... However, the carb (or carbs) only feed one cylinder at a time.... so it doesn't really matter how many you have..... or (for SUs) how big it is. A bigger carb doesn't supply any more air than the engine wants. A carb that's too big or too small will be "slightly" less efficient - but we're not talking sheep stations.

The threads in both the original pictures looks pretty clean. The ends of the plugs protrude into the combustion chamber so will always have a carbon build up. As I said before the inner cylinder will always run richer on a single carb. My concern was the actual thread on plug 2; look at the peak of the thread at the outer end ... to me it looks flattened. Maybe the plug was dropped onto a hard surface??? If it was then forced into head it may have damaged the threads in the head?? You should be able to insert a new plug using light finger pressure ... only the final nip up would need a spanner (don't put any oil on the plug threads).

I wouldn't worry.... A Series are incredibly tough .... and durable. I drove a (mate's) Squealy Fright from W'gong to Sydney once. Its was pretty smoky on the highway. When we pulled it down we found most of the piston rings missing...

Good luck, Ian