• 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 popping

Share this page

tri_carb_healey

tri_carb_healey

Senior Member
Offline
Hey Guys,
I noticed a popping sound in my third carb sounds like a backfire. Sometimes when this happens a little smoke shows up, but not everytime. What is this a symptom of in SU carbs?
 
Backfire is usually associated with a lean condition, but honestly, diagnosing a carb problem on the internet would be akin to saying "I don't feel well."

There are so many steps to insure that the carbs are synchronized and in tune, that putting your attention on just the #3 carb is just skimming the surface.

Three (3) carbs doesn't necessarily make the job more difficult, just one (1) more carb to deal with, and the all the same steps used on #'s 1 & 2 are repeated for #3.

When was the last time the engine had a complete tune? Starting with setting the valves, replacing and/or setting the points (condenser, cap checked for "tracking", rotor, wires tested for resistance,new or cleaned sparkplugs, etc.) checking and setting the timing are ALL preliminary steps to "setting the carbs."

I don't know who said it first (Steve Smith?), but it's an age-old quote: "most carburettor problems are electrical..."
 
well i was trying to start the car today and it caught fire... from the third carb. I was able to put it out but now everything is coated in flame retardant. I think i'll start by cleaning up the mess and turning my attention to rebuilding the distributor.then finding someone to help me see if the valves are set properly.
 
Whoa, boy if a car catches fire from one of three carbs, although Randy's views are justifiably respected, if you are just a home garage hobbyist, even without taking off the carb,just removing the dome, piston, checking jet, butterfly, float chamber, and needle position should use up about an hour of easy chores before rebuilding a distributor and getting into the valves. Not sure how distributor or valves can lead to excess gas at one carb to extent of catching fire. Maybe even a fuel leak (gas line or carb) ignited by ?, Anyhow, good luck.
Jay
'65 3000
 
why said:
Whoa, boy if a car catches fire from one of three carbs, although Randy's views are justifiably respected, if you are just a home garage hobbyist, even without taking off the carb,just removing the dome, piston, checking jet, butterfly, float chamber, and needle position should use up about an hour of easy chores before rebuilding a distributor and getting into the valves. Not sure how distributor or valves can lead to excess gas at one carb to extent of catching fire. Maybe even a fuel leak (gas line or carb) ignited by ?, Anyhow, good luck.
Jay
'65 3000
Click to expand...
Reread his initial post, then reread my response to that__what other information did I have to go by?

His second post, the third in this thread, discloses the gravity of the situation!

I still stand by my recommendation, because: if the needle valve was sticking, allowing the float chamber to overflow the jet well, then an engine backfire could, and apparently did, ignite the fuel in the carb's throat.

It's still an electrical issue that caused the backfire, there just happened to be an over-abundance of fuel to set ablaze.

And, now we know the whole story, which is why I have to laugh when someone posts (here of on the BMW boards I frequent) "my car's not running right, what's wrong?" Not much to go on, but we make a stab at it, only to be shot down afterwards when the real story emerges.

The internet...
 
yea, I'm still a huge noob. I'm going to clean up the mess made by my extinguisher. order a rebuld kit for the carbs and rebuild the distributor then deal with the timing....
 
I recently rebuilt the carbs on my 62 tricarb, and one of the problem spots will probably be the throttle shaft. It wears and then leaks vacuum. There are two solutions to the problem. Get rebuild kits with slightly oversized shafts and have a machine shop ream the hole to the new oversize. Or, get new bushings to install in the body and use a (new) original sized throttle shaft.

I went for the first option, and it seems to be working fine. The kits came with good instructions and the exact size for the new hole (don't try it yourself--take it to a machine shop). I think that if they ever wear out again, I can still use the second option.

Hope this helps,
Keith
 
Back
Top