[Healeys] Another backfiring question

[Bob Spidell]

I dunno if it can cause high RPM backfiring (I think it could), but the 
airflow on all (2-3) carbs has to be the same--or, at least, very 
close--at all throttle positions. This has to be checked off-idle, 
obviously, but if it's good at, say, 2,500RPM it should be good at all 
speeds; if not, you have to disconnect the throttle connect shaft to set 
them. I suppose a crack Brit-car mechanic can test with the recommended 
'hose-in-the-ear' technique--my ear hose is collecting dust 
somewhere--but I use a Uni-Syn.

To paraphrase the TV commercial we've all (probably) seen a thousand 
times: "If you don't have a carburettor synchronizer, get one."

Bob

On 1/29/2021 6:13 AM, healeyguy--- via Healeys wrote:
> Len and Listers
> Pushing the pin up to lift the piston is the start of the "test the 
> mixture setting" exercise. You begin the push, ever so slightly,  and 
> listen to the idling engine. The idle goes up.  What do you do next? 
> You continue to raise the pin  to see what happens. If the idle 
> continues to rise you know you are in a rich condition. If the idle 
> stops going up and starts to drop off the mixture is pretty close. If 
> the idle does not increase from the start you usually assume you are 
> in a lean condition.  This gets the carb mixture close at idle which 
> in theory means the carb is going to operate throughout the RPM range.
>
> There is one other assumption here, that being that the carbs is in 
> the same condition as new mounted on an engine operating as new. That 
> is when allot of other stuff comes into play.  The carb float bowl 
> items, needle/seat and float level  must be set correctly. Float must 
> not be leaking thus making it sink. Carb must have the correct main 
> needle and jet and they have to be installed and adjusted correctly. 
> Flutter at high RPM may indicate that the piston spring in the suction 
> chamber is weak or the incorrect spring installed. Ignition timing and 
> condition and setting of ignition points.
> The list goes on and on......
> P
>
>
> -----Original Message-----
> From: Leonard Berkowitz <DrBerkowitz at hotmail.com>
> Subject: [Healeys] Another backfiring question
>
> Hi all
>
> Just finished repairing and reinstalling the carburetors on my BJ7. I 
> thought I had everything adjusted properly. According to my Haynes 
> Manuel the engine speed should increase slightly when you lift the 
> piston a very small amount. Mine does that.  My dwell angle is where 
> it needs to be and the car starts and idles nicely. Also sounds 
> beautiful when I punch the accelerator linkages. The problem is that 
> when I get it up to 60-70 mph I get what sounds like backfiring into 
> my carburetors. Also sounds like it doesn’t have a whole lot left in 
> the tank, so to speak. Does that sound like I am running too rich or 
> too lean?
>
> Len Berkowitz
>
>
>

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