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Austin Healey Engine Noise


I have a newly rebuilt engine on my 1965 Austin Healey 3000. When the engine is cold it makes a popping/backfire noise. After the engine has warmed up for 10-15 minutes, it doesn’t make the noise anymore. See this video at 0:19-0:20

Any thoughts?

Thanks in advance.


Sounds like a lean misfire/backfire…See those brass hex fittings on top of the SU carbs? Remove them carefully and check to see that these slide dampeners are almost full of ATF…The carburetor slides must be dampened or they will jump around and disrupt the carburation…

That sounds like the most likely cause, Caddyman. Have you enjoyed adjusting some SUs?

Many, many of them…I got pretty good at it…They are a great design, except for the choke method and function…

I helped my brother sort out running issues with a mid-60’s Healy 3000 MKII. It was tricky but fun taking test rides to see if we had found the sweet spot. As an owner you really need to get into dealing with the carbs on this motor. They are finicky and only a few mechanics today would know what to do with them.

Find yourself a Healy owners club, join and go pick their brains. I was only a helper tool passer on this job, but I heard enough 4 letter words over 3-4 days to know these babies are tricky. Once you get it these cars are just loads of fun by the ton. If you have the free flow exhaust the sound is just music.

Listened again to the video. Are you sure the valves are properly adjusted? It seems carbs most likely. Valves out of adjustment a possible, spark advance not working properly (not sure if this is a vacuum advance, mechanical, centirifical, or combo) but the advance might be slow. Check that with a timing light and watch the timing marks change from idle as you increase rpms. Check the points, either via dwell meter or feeler guage.

I listened to the video and it sounds like the valve lash may be a little tight. I would recheck the valve adjustment first. Once the engine heats up the valve lash will get a little looser so that could be your problem since the noise goes away. If the valves are set right then it’s time to get those carbs checked. The exhaust and intake valves are usually set to two different tolerances. Uncle Turbo is right. The carbs are super finicky and it takes finesse to get them adjusted properly.

I finally had a day to take care of this. I adjusted the valves as suggested, they required a very few minor tweaks. Then I went about adjusting the carbs. When I pulled the damper covers off, and then the dampers, the problem was immediately apparent. The metering needle wasn’t attached, so when the damper lifted, the needle stayed in place. Once that was properly secured, and the carbs were tuned, it ran like a champ. Thanks for the advice!