Non-Speedster mixture question

I rebuilt and tuned the SU carbs on Mike Lempert's '56 Austin Healey 100 recently, and the car seems to be running great, but a bit hot. It also has been running on a little when you turn it off. To me, that says the mixture is too lean. I tweaked the carbs today and it is still running great, but it still runs on. We didn't drive it far enough to see if there was an overheating problem. Prior to rebuilding the carbs, the car sat for a good 6 months. Before that, the car ran ok, and didn't overheat, but it leaked gas like the BP oil rig leaked oil. It's a wonder we didn't have a conflagration, I tell you!

Any thoughts?

SUs are a pain at times..... The variable venturi effect is great, but will allow decent engine performance with a criticaly lean condition..... Find an exhaust analyzer, and get a good diagnosis.... Or it could be LUCAS distributor advance problems. (I cracked a head due to this one.)

Did you swap the fluid out? Makes all the difference in the world on an SU.

angela

Yup, swapped the oil in the dashpots. I'll probably enrich the mixture a bit more and see. Given the time it sat, and Mike's tendency to, um, let things go until they break, it could be totally unrelated.

Run on like your talking about is caused by carbon build up. Once the engine warms up the carbon gets hot enough to ignite the fuel. Run some Chevron Techron throught the system a couple or tanks worth. This should clean up the carbon issue. I do recomend checking the fuel air mixture also as this may be a two part problem. One other thing to listen for is pinging when under load and a lean misfire going on when idleing. If you hear a lean misfire I would check for air leaks.

Needs a good "Red-neck Tuneup" with a jug of Sea Foam to get rid of carbon buildup.

It's running very smoothly, with no misfiring at idle or during cruising. The only time it isn't perfectly smooth is when you downshift - then you get that lovely Healey blurble.

Got some Sea Foam and will try that. I will also pull the plugs and check them. Finally, I will check his radiator to make sure he hasn't let the coolant get low.

All are good suggestions and in addition, check the ignition timing

sea foam... gotta try that.

Once in the long gone days of yore we had some carbon build up in an old truck 350 that'd done several years duty in a station wagon that was used as a delivery vehicle for a liquor store. The engine had run about 40,000 miles with no highway use at all. So of course I yanked it and stuffed it in my old Nova, drove it 100 miles to college and, once there, promptly revved it up to about 5500 in second gear. Came back to the parking lot and noticed she'd developed a hella knock.

Sounded like a rod knock.

So, flat-bedded her home, pulled off the oil pan and looked for broken parts. Found none. All the rod and main bearings checked out, so we put the pan back on and started her up and heard that tell-tale clunk clunk clunk.

The Boss comes over with a little tube like from a radiator overflow. He fills up a drygas container with tap water and puts one end of the tube in that, then unplugs a vacuum port on the carb and plugs the other end of the tube on that.

GRRRUSH! blurble! GRRRUSH!

He's revving the engine up with one hand while judiciously dunking the tube in and out of the water. Ran the whole pint through it. Steam's coming out both tail pipes.

In about 50 seconds it was done. No more knock. She ran good for another 18 years after that--probably is still running good.

check total advance on dist. you should have between 35 and 38 degree, if its less it will see mlazy. last winter i did a morgan wit hthe same carbs , the problem was the dist, petronia sells a new dist with electronic unit in it already. less than 200. the owner loves it. bill

Ed, did that on my Spyder engine when it was newer than now. After about 5000 miles, it was pinging pretty bad. Took the air cleaners off, and revved it while trickling water down the throats, one at a time. LOTS of white steam/smoke, and problem solved. Basically, you are steam cleaning the carbon out of your engine. Works well, just don't pour it in and hydro-lock the engine. You WILL bend a rod, not good! BTW, after talking with Jake on the phone, this is what he recommended I do. Haven't had to do it again since.

Danny, How much water and about how fast did you pour it? I'm sure i could use doing this from running a tad rich.

~WB

We use to do this all the time with the older basic V-8's

Bill, about a pint in each throat, poured in at a drizzle, increasing until you get a nice BIG cloud of white smoke.