• Hi Guest!
    You can help ensure that British Car Forum (BCF) continues to provide a great place to engage in the British car hobby! If you find BCF a beneficial community, please consider supporting our efforts with a subscription.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

Carb Tuning for Cold Starts

Share this page

craigshealey3000

craigshealey3000

Member
Bronze
Country flag
Offline
A trusted friend of mine tuned my Healey SU carbs and it runs stronger than before, but now cold starts are really difficult. How do I rectify this?
1967 AH 3000 BJ8.
 
My SWAG is choke adjustment. Make sure your choke cables move smoothly and easily (as much as possible). Make sure there is very little--you need a little to make sure the arms return properly--slack in the choke cables or the choke control 'body' on the firewall (nothing stops the cables from sticking out at the block which pulls two cables with one). The jet lowering arms should start moving up with (almost) the first pull on the knob. Also, if your car was running way rich your friend may have tuned it too lean; esp. if he tuned with Colortunes (Big Healeys aren't gonna give you a perfect stoichiometric mixture and still give full power). The 'book' says there should be a gap at the throttle adjustment screws; I never like the idea of the throttle plates slamming against the throttle bodies, so I tune mine to just touch the levers, which opens the throttles a tad more. The 'book' also says tune for a 600RPM idle; I'll bet most of us run a little higher than that, esp. with any sort of uprated cam--like the DWR1--and the idle will vary with conditions. Mine, for instance, tends to lug when hot on a hot day (likely from running rich).

A 'trick' I learned years ago is to press the accelerator pedal to the floor before you pull on the choke knob; makes it easier to get full travel on the cables. You can twist the knob to (sort of) lock the choke on.
 
Bob_Spidell said:
My SWAG is choke adjustment. Make sure your choke cables move smoothly and easily (as much as possible). Make sure there is very little--you need a little to make sure the arms return properly--slack in the choke cables or the choke control 'body' on the firewall (nothing stops the cables from sticking out at the block which pulls two cables with one). The jet lowering arms should start moving up with (almost) the first pull on the knob. Also, if your car was running way rich your friend may have tuned it too lean; esp. if he tuned with Colortunes (Big Healeys aren't gonna give you a perfect stoichiometric mixture and still give full power). The 'book' says there should be a gap at the throttle adjustment screws; I never like the idea of the throttle plates slamming against the throttle bodies, so I tune mine to just touch the levers, which opens the throttles a tad more. The 'book' also says tune for a 600RPM idle; I'll bet most of us run a little higher than that, esp. with any sort of uprated cam--like the DWR1--and the idle will vary with conditions. Mine, for instance, tends to lug when hot on a hot day (likely from running rich).

A 'trick' I learned years ago is to press the accelerator pedal to the floor before you pull on the choke knob; makes it easier to get full travel on the cables. You can twist the knob to (sort of) lock the choke on.
Click to expand...
Great advice, thanks! The choke cable is working and I brought the fast idle up a hair and it is better. I wish I could find the right Choke knob without buying the entire cable, my knob has a fan symbol on it! Next project: insulation for my "hot box" warm weather is coming!
 
Back
Top