Carb & Needle ZS CD carb

[wbdvt]

Hello,

When I bought this car, 1980 Spitfire, in the fall the air piston in the carb was stuck. I rebuilt the carb and installed a new needle. There was no brass number tag on the carb, so I went by the table in Moss Motors catalog and ordered a 45N needle. When I took the carb apart the needle was a 45L, which would be for a 1977 Cal car. I doubt that the car is from California and ended up in VT.

I am still running rich and have turned the needle as far left as it can go. Since the exhaust system has been replaced with what looks like a performance free flow exhaust system, could that have necessitated a needle change to get the mixture leaner? I am using a Colortune to judge the mixture.

Thanks all in advance for reading and replying.

 

[Don_R]

Don't be surprised if it is a Cali car. The parts car I have the motor and trans out of is a Cali car and I am in PA.

BTW what is the motor # stamped on the block?

Should start with FM...

 

[wbdvt]

Hi Don,

Ok, maybe I assumed it would not be a Cal car. The number on the block is FM128568UCE

 

[wbdvt]

Hi Don,

I just looked at a chart of engine block codes and it appears that the "C" in the suffix indicates that at least the engine was from a Cal car. But with all the mods done (exhaust system, EGR gone, etc) would this still need a 45L needle? I have no problem re-installing the needle and seeing if I can lean out the mixture more.

 

[Don_R]

Thats why I asked...Don't like to assume...

Its worth a try.... How was the float level when you rebuilt the carb. fuel too high in the bowl might be a problem.

Did you change anything on the intake side. i.e. unsing a high flow air filter?

I take it you already checked the valve lash, timing and plugs, good spark to the plugs.


My spit is a little rich in the exhaust but the plugs look good at Idle so I haven't bothered trying to correct it.

 

[wbdvt]

Hi Don,

It came with a high flow air filter. The float height was okay and I did check the valve lash. The spark originally looked weak and I replaced the coil and the spark looked a lot better.

Thanks
Barry

 

[Don_R]

Barry,

As I have been learning about these carbs, the high flow filters can change the air flow enought to need a different needle.

hopefully someone will pop in that has already had this prob..

I'll be fightin this fight when I get the dual SU carbs rebuilt.

 

[wbdvt]

Don,

Well, the way I see it, if it is the original carb on this California engine, I should go back to the 45L needle and see how much that allows me to lean out the mixture.

I also have a misfire on all four cylinders but that could be due to the soot build up on the plugs. I figure I'll get the mixture correct, put new plugs in and see if I get the misfiring then. Since this has a Allison XR-700 electronic ignition which looks original as it has a RCA canned transistor mounted to a large heat sink, I wonder if it is at it's end of life.

 

[tr8todd]

Is there a chance you are getting unmetered fuel from the choke mechanism some how? Common problem on the TR7 and TR8 zeniths.

 

[wbdvt]

tr8todd,
Good question as the choke is funky. It is a conversion to a manual choke and seems to work only in full open position, try to close it and cuts out engine.

 

[tr8todd]

That's because you have the needles fully adjusted down. Sounds like your running at idle on choke delivered fuel only.

 

[wbdvt]

Thanks, good observation. I will change the needle back to the 45L and see what changes that makes. Should have everything straightened out by the time VT driving season arrives!