Running rich

[fordtrucks4ever]

My 67 has always run rich. The plugs and exhaust are dry black. I have been thru the carbs twice in the last 12 years. Engine starts and runs fine. Always get at least 17 mpg. Everything is original or stock replacement parts. I have tried different oils in dampers with no affect. I dont know what needles are in carbs. Is there a way to identify which ones they might be? The car runs well with exception being a little sluggish on accelleration. It doesnt miss or hesitate, just slow to rev up. A Healey owner had mentioned that to me after driving mine. I have never driven another big Healey to get a comparasion tho. Any suggestions would be greatly appreciated. Thanks, Terry.

 

[Michael Oritt]

Terry--

Working one at a time to avoid confusion remove the carb bell housings, set them carefully aside and remove the carb pistons and invert one in your hand so that the needle is sticking up. Notice that there is a hole with a locking screw along the circumference of the piston perhaps 1/8" below the top edge and with a small slotted screwdriver you can loosen the screw and remove the needle.

Get a magnifying glass and on the raised shoulder of the needle there will be a series of numbers/letters etched into the surface--that is your needle type. BTW is the needle straight (roll it on a piece of glass), scratched, pitted, etc? You can straighten and polish them if need be. Also do the pistons fit well in the bell chambers or are there scratches, gouges, etc.

Be sure and make a mental note of just where the shoulder was in relationship to the piston--it should be flush and if is oo far in or out you should correct this, which in an of itself will affect the mixture as it effectively changes the needle's taper in the jet and leans or richens accordingly.

You may also want to examine the springs-what is their color,length, etc. Data on correct needles and springs are in your manual.

Report back.

 

[BUNDYRUM]

Hello fordtrucks4ever, to determine which needles are in the carbs you need to remove the tops and lift out the pistons.
The needles are located in the bottom of the pistons with a screw in the side of the piston near the bottom.
There are 3 main sections of the needle. The parallel section at the top is called the shank, just below this is a groove and then the tapered section that determines the amount of fuel delivered.
Before removing the needles look at where the needle is positioned in the piston.
The correct positioning for the needle is the upper edge of the groove (which is the same as the lower edge of the shank) should be level with the lower face of the piston
You only need to undo the screw 1/2 of a turn at most to allow the needle to be removed.
On the shank of the needle (the part of the needle that locates in the piston) there should be 2 letters stamped. This is the model of the needle and for a BJ8 it should be UH for the standard needle.
The choice of oil in the damper is apparently a bit like underwear, everyone swears by their choice, yes I have my choice also.
Best regards,
bundyrum.

 

[steveg]

My 67 has always run rich. The plugs and exhaust are dry black. I have been thru the carbs twice in the last 12 years. Engine starts and runs fine. Always get at least 17 mpg. Everything is original or stock replacement parts. I have tried different oils in dampers with no affect. I dont know what needles are in carbs. Is there a way to identify which ones they might be? The car runs well with exception being a little sluggish on accelleration. It doesnt miss or hesitate, just slow to rev up. A Healey owner had mentioned that to me after driving mine. I have never driven another big Healey to get a comparasion tho. Any suggestions would be greatly appreciated. Thanks, Terry.

My car with UH needles runs rich all the time and delivers 16-17 mpg at best on a trip. A good deal less in spirited driving. I have 2 K&N Air/fuel meters and they show the car runs all rich all the time - with the mixture at the power end of the range even at cruise.

Moss has listings for the standard UH, as well as one richer and one leaner needle - UL.

Joe Curto in Queens
https://www.joecurto.com/
can sell you needles, as well

IMHO I wouldn't go to a leaner needle than the UL without installing an air-fuel meter - due to the danger of holing a piston if running too lean.

The big piston return spring comes in two colors: red & green - this in combination with the damper oil constitutes the accelerator system on the SU.

 

[Michael Oritt]

Steve--

If you are simply shutting down the engine from fast idle or whatever the chances are that the plugs are always going to look like they are rich.

On the Elva race engine admittedly I am more concerned with my mixture in a a rather narrow RPM band (4-5K) but I always try to switch off the ignition from WOT and coast to the pit wall, then pull the plugs one at a time and see what they tell me. I'd bet you would see a difference in the color (very possibly more to what you seek) on the insulators doing it this way with no other adjustments having been made.

 

[Bob_Spidell]

Steve, is your car positive-ground? If so, how did you set up the K&N mixture monitors?

 

[fordtrucks4ever]

Is anyone using the leaner needles on stock setups? Was there much noticable difference?

 

[Randy Forbes]

If the center jet bearing in the SU is not set exactly right, the needle will rub on it, with the resulting wear changing its profile; in other words, making it run richer by allowing more fuel to pass by the needle.

Take a good look at your existing needles under a magnifying light, if possible, to see any signs of wear. You may be able to run fresh standard needles and clear up the condition.

Considering your location, I doubt it is the altitude affecting your tune.

 

[Keoke]

My 67 has always run rich. The plugs and exhaust are dry black. I have been thru the carbs twice in the last 12 years. Engine starts and runs fine. Always get at least 17 mpg. Everything is original or stock replacement parts. I have tried different oils in dampers with no affect. I dont know what needles are in carbs.


Is there a way to identify which ones they might be?---Yes If you remove the Needle you will see engraved on the shank the Mixture code for the needle.Fwiw--Keoke


The car runs well with exception being a little sluggish on accelleration. It doesnt miss or hesitate, just slow to rev up. A Healey owner had mentioned that to me after driving mine. I have never driven another big Healey to get a comparasion tho. Any suggestions would be greatly appreciated. Thanks, Terry.