Packard Forum Index » Pre-War (1899-1942)

Hello-

I have a 6 cyl with an updraft Detroit carburetor.

. When the engine is cold it does not start if I choke it even 50%. If I use the engine primer cups without any choking, it starts right up.

I always pull the spark retard all the way out and then quickly push it in as soon as the engine fires.

If I choke it, the choke only pulls out 1/2" maximum. (internally the carb is fully choked) I usually try and pull it out about 1/4" which sets the carb at about 1/2 way. Either way, if I crank if more than 3 seconds I will get gas dripping out of the lower air intake.

Any thoughts on this?

Thanks

Hello Gar, I have a 533 with the same carb. I also have heaps of English motorbikes. Cutting to the chase. I turn the vac tank on and lift the float needle until fuel runs out of the inlet. I then get inside and operate the starter with probably half choke and it fires right up. In my experience
( with approx 65 bikes) You have to flood the carb on all Twenties and Thirties English bikes, yes, even Brough Superiors. I would suggest that the problem is that you are retarding the ignition. Totally unnecessary as your comp ratio is approx 4.8 to 1 and you are using around 90 Octane fuel instead of around 65 Octane. And, if all else fails, what's wrong with using the priming cups? They are also great for finding a cylinder that is misfiring. Good luck. Peter Toet.

Peter:

I will go over to the garage and try your suggestion.

I identified the trouble of cold starting my car. It seems that there is about a 1/32" air gap round the aux air valve. Because it doesn't seal correctly, it admits too much air into the carb when it is cold and it wont start. If I manually close this gap, it starts up on its 2nd attempt. Everytime.

The aux air valve doesn't close correctly because the cam, which pushes up against the air valve on full choke, is not hitting the bottom of valve correctly. Any suggestions on fixing this issue? Is there an adjustment on the cam that I am overlooking?

Thanks

Is there a thick gasket between the air valve assembly and the body of the carburetor that can be removed?
If its not that it would be a simply matter to build up the cam a little, its not a critical profile, its only function is to hold the air valve shut when the choke is operated

No gasket.

I am thinking that I could make the cam push more securely against the aux air bell by adding a drop of solder on it.

Any thoughts on that?