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Carb Noise

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J

JJS

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I have a '60 3000 with a BJ8 cam and HD8 carbs. It runs well, but the carbs make a lot of noise during idle. Like a big sucking sound. Once I give it a little throttle the noise drops off. I wouldn't have thought anything about it, but a friend asked me what was wrong with the car? Is this normal?

Thanks

Joe
60 BN7
 
Check for leaks around the intake manifold by spraying with windex or carb cleaner where the manifold meets the head. I had a wierd noise which might have been similar to this when I mounted my headers as the thickness was slightly different from the intake manifold which caused an air leak. I wound up doubling up on gaskets on the intake portion of the manifolds.

Another possibility is the guts of the air cleaners have gone away, resulting in a sound similar to that of no air cleaners.
 
JJS said:
I have a '60 3000 with a BJ8 cam and HD8 carbs. It runs well, but the carbs make a lot of noise during idle. Like a big sucking sound. Once I give it a little throttle the noise drops off. I wouldn't have thought anything about it, but a friend asked me what was wrong with the car? Is this normal?

Thanks

Joe
60 BN7
Click to expand...
The HD8's on the BJ8 have a very noticeably louder "hiss" than other carbs on other big Healeys. If idle is fine that may be what you're hearing. If they're "hissing..their fine", as it was explained to me over 40 years ago by a "real" Healey mechanic.
 
Patrick67BJ8 said:
The HD8's on the BJ8 have a very noticeably louder "hiss" than other carbs on other big Healeys. If idle is fine that may be what you're hearing. If they're "hissing..their fine", as it was explained to me over 40 years ago by a "real" Healey mechanic.
Click to expand...

Patrick, I have had some trouble adjusting the idle to below 1200 rpm when the engine is warm. Could this indicate an air leak in the manifold?

Joe
 
JJS said:
Patrick, I have had some trouble adjusting the idle to below 1200 rpm when the engine is warm. Could this indicate an air leak in the manifold?

Joe
Click to expand...
The only way to adjust HD8's is to have them warmed up. If you leave the car sitting for a while and then try to adjust them you'll have eratic readings. Be sure to drive the car around the block if you left the car sitting for any length of time while working on it.

Also, one of the biggest problems of misadjustment with HD8's is the slow run valve adjustment. Most people don't understand how it works. Be sure you've got the carbs rich enough too or you'll never get it to idle. Be sure to have them syncronized and make sure the throttle linkage is set so that they both open at the same time.

Air leaking at the throttle shafts will make the engine idle faster too. Is your shafts good and snug or can you feel a little play in them?
 
I've got HD6 on my car. Basically the same as the HD8. They make this hissing sound when the slow run valves have been used to adjust the idle. The throttle discs are shut. If you would close the slow run valves and adjust the idle using the throttle disc screws like you would on many other SU carb designs, the hissing sound disappears. That's how it works on my car. . . . . But I like the hiss.
 
johnea said:
I've got HD6 on my car. Basically the same as the HD8. They make this hissing sound when the slow run valves have been used to adjust the idle. The throttle discs are shut. If you would close the slow run valves and adjust the idle using the throttle disc screws like you would on many other SU carb designs, the hissing sound disappears. That's how it works on my car. . . . . But I like the hiss.
Click to expand...
I believe the slow run valves eliminate the readjusting of the throttle linkage between the two carbs after doing carb adjsutments. Getting the linkage set just right can take some time and is best checked with the carb tools...the ones with the small wires that attach to the oil reservouirs inside the carbs. The HD's seem to be slightly better adjusted with the slow run valves and cracking open the butterflys a "skosh". I'm told that this eliminates any hesitation when starting from a dead stop.
 
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