I am Way Too Rich!!!

[John Kuzman]

Not me, my ’59 Bugeye! Finally got around to doing a tune-up on my recently acquired BE. I knew from the first time I ran the car that it was running on the rich side, especially when up to temp. At idle, you could see the black suet spitting out the exhaust.
I changed points (set at .015), condenser, coil, rotor, cap, plugs (Champion N9YC @ .025) and wires. Set static timing at 5BTDC (as best I can tell from looking at the marks underneath). Rather than struggle with changing the points in place, I set up a spare DM2 distributor, then swapped out distributors.
Fired right up, idle is fast (about 1200 rpm) and timing with a dial-back light is way advanced (25+BTDC @ 1200 rpm. Vacuum advance line is disconnected.
Ran up to temp., pulled plugs, black as coal! In fact, there is enough carbon on all plugs to fire an old coal furnace!!!
I usually follow the theory that 99% of all carburetor problems are ignition related, but is it time to mess with the carbs? Would a higher heat range plug make a difference? Float problem allowing too much fuel? Jets appear to be flush when I manually lift the pistons.
I believe the carbs are later HS2s, 1.25”. The tags on the float chambers do not make sense to me. They are AUD69F and R. The engine tag is missing, but I think it is a later 948, I can see what appears to be a 950 stamping on the block, below the intake side.
Any advice appreciated.

John Kuzman
’59 AN5
’63 BJ7
’69 Corvette

 

[jcatnite]

Not real familiar with the HS2's but if you know your ignition is good (check low tension leads and coil resistance as well) then you might take a look at the choke settings. Make sure it isn't partially still on which would make you run rich as well. I'm sure someone who is familar with those carbs will be along soon.
JC

 

[piman]

Hello john,
if your Sprite is a 948 cc they shoud have a pair of H1's, ref AUC863, AUD 69f and R (Front and Rear)are from an M.G. 1100 saloon car.
However, they should work OK on your engine, depending on the needle fitted.
One, the jets should not be flush with the bridge, they should be down two full turns of the jet (mixture) adjusting nut. Points to check are:-, the needle shoulder should be flush with the bottom face of the piston, the choke is not sticking, although that seems very unlikely if the jet is flush as you say, the carburettor(s) is not flooding.
If you take the piston\dashpot assemblies off, and switch on the ignition, fuel should be seen about 1\8" below the top of the jet and the fuel pump should not be ticking at that level. Finally a simple check to see that your air filters are not badly clogged.
Plug type will not cure your problem either.

Alec

 

[ThomP]

John. One of the things that happens to old cars is that the fuel lines get crudded up. When this happens, the fuel does not stay at the proper level in the fuel bowl. With the fuel level too high, the car runs rich. If you haven't serviced your fuel system lately, give this a check, it's easy. Remove the 3 screws holding the cover on the fuel bowl. Look at the bottom; if it has junk, then it is likely the needle valve in the float chamber is not closing properly and the overfill condition is happening. The temporary solution is simple. Clean the fuel bowls, replace the rubber fuel lines near the carb and add an in-line filter. I prefer the see through types so I can see is the remainder of the fuel system is providing more junk.

If the jets are flush with the bridge as you say, it is a sign that the previous owner tried to lean the overrich condition caused by the flooded fuel bowls, but (of course) couldn't get it lean enough. Piman is right, two full turns down (12 flats as some manuals would say) from flush is a good starting point for tuning once the flooding problem has been eliminated as a problem.

1961 & 1962 948 sprites came with HS2 (AUC990). I don't think that the AUD69 set was original to your car, but they should work just fine.

One other thought the standard needle for an 1100 was "D3", while the standard needle for the 948 was a "V3". I don't know the difference between these needles, but it is worth a check to see which set you have. I wouldn't suspect this as the problem, until the above issues have been addressed.

Good luck

 

[piman]

Hello all,
a point that has been mentioned before, but worth repeating is that all needles (of the same size group) have virtually the same idle dimension, so the needle is not a factor in setting idle mixture. That is not to say that any needle will work well, but don't say the needle is wrong if the idle mixture is wrong, the needle doesn't matter at idle.

Alec

 

[John Kuzman]

I am Way Too Rich!!! - Update

Well, excellent advice from all responders. ThomP and others may have hit the primary problem. Pulled the covers off the fuel bowls and there was some "crud". Cleaned the bowls and reset the float to spec. I am now able to get the idle down to about 800 RPM without bellowing thick, black smoke. Also able to get the timing @ about 8 BTDC at idle per my dial-back timing light.
I know there are pros and cons to the use of the colourtune device, but I gave it a shot. Nice burn at idle, but still rich on gradual acceleration to 2500 rpm. No adjustment left on the jet adjusting nut, i.e. pretty much all the way up.
I am going to clean the plugs and run the car for a few days and look at the plugs again. I may even experiment with leaner needles if I start feeling adventurous! In the end, I may pull the carbs after the driving season and ship them to Joe C. for a complete going over.
Thanks for the words of wisdom.
John

 

[piman]

Re: I am Way Too Rich!!! - Update

Hello John,
there is still something wrong, as I said needles have little or no effect at idle, so a different needle will still have your jet adjusted far too high. Are the needles' shoulders flush with the piston?, this is a basic rule.
Ensure that the jet is a 0.090" jet and not a 0.100 which is fitted to larger HS carburettors. (the idle dimension of the needle is 0.089" so there should be very little clearance if you put the needle fully into the jet, this is a quick check)
A point with colortune, if there is oil getting into the combustion chambers they will show rich.

Alec

 

[ThomP]

Re: I am Way Too Rich!!! - Update

John, It is my understanding that the carbs are supposed to be rich on acceleration. This is the SU equivalent of an accelerator pump found in fixed jet units. Rich on acceleration is OK. I think your approach to checking the tune is good: Use the car for a while and check the plugs.

As an aside, depending upon other engine components, some LBCs really want to run rich to run happily. My big Healey is an example of this. I have the carbs set using a gas analyzer. They are set to about 3.5%, because any leaner and I backfire for the first hour of operation (not fun). At 3.5%, the choke needs to be out for about 15 minutes befor she'll run happily. The plugs are brown to sooty black on this car. My favorite mechanic keeps telling me to make her richer, so far I've resisted, because the plugs say "rich", but he's seen many more 3000s than I have, so I'll probably give in and tweak it a bit further.

 

[piman]

Re: I am Way Too Rich!!! - Update

Hello Thomp,
it sounds to me as if your engine is far too slow in getting up to operating temperature, and I would not be inclined to make it any richer. It does not do your engine any good to have the choke out for so long from a wear point of view, (apart from the cost of fuel, particularly in the UK at 90+ pence per litre).
An engine on the rich side will give most power but you can go too far; you may also like to look at your ignition timing as you may need a little less advance.

Alec

 

[ThomP]

Re: I am Way Too Rich!!! - Update

Hey, 26 MPG on the highway. How many Big Healeys get that? (Ok, Ok 15 around town like normal). Put a gas analyzer on these engines. You'll be surprised how rich they run!

Thanks to the lack of octane, the BJ8 and the Corvair are both retarded 2 & 3 degrees from "factory"

 

[Dave Russell]

Re: I am Way Too Rich!!! - Update

Getting back to the original problem,
There is a very real possibility that the jets and or needles are worn. Even a thousandth or two would screw up the idle calibration. It doesn't cost very much to replace the needles & jets. This woud assure you that one part of the combination is correct. The D3 & V3 needles both have the same diameter on the first two steps - .089" & .085". The GG needle would be leaner on the second step at .087" which might help.
D

 

[startech47]

Re: I am Way Too Rich!!! - Update

Is there a good reference on SU needles and jets?

 

[piman]

Re: I am Way Too Rich!!! - Update

Hello ST,

www.burlen.co.uk, jets are the same for a specific carburettor and I think are three basic sizes, 0.090", 0.100" and 0.125". Needles have a much bigger range and must be matched to the correct jet. You can get a very detailed S.U. maintenance and parts book from Burlen and they also publish a needles reference book listing all the available needles and their dimensions.

Alec