1954 Carb popping

[Ted K.]

A good running 1954 with everything pretty close to specs. When under acceleration or racing up the engine from under the hood there is a popping sound that comes from the rear carb.
Any ideas???
Ted

[Chris S.]

Re: 1954 Carb popping

check /adjust your mixture screw - on top - or check for a vac leak

[Edward J.]

Re: 1954 Carb popping

A good running 1954 with everything pretty close to specs. When under acceleration or racing up the engine from under the hood there is a popping sound that comes from the rear carb.
Any ideas???
Ted

Ted is it possible you may have a valve adjusted to tight?? maybe on one of the last two cylinders.

[Ted K.]

Re: 1954 Carb popping

It idles pretty smooth so I wouldn't think a tight valve, but what else is there. I will check it out.
Thanks

[Ed S.]

Re: 1954 Carb popping

Correct me if I am wrong but the only way you can get popping back through the intake system (in this case a carburetor) is for combustion pressure to be vented via an open or partially open intake valve. You indicate that a) you are confident of the adjustment and b) it happens when accelerating (I assume higher RPM ranges). A weak or incorrect valve spring will allow a valve (or valves) to "float" - to remain partially open at higher RPMs - this would allow for the popping noise you are hearing. At normal or lower rpm ranges they work perfectly - it is only until you get up into higher RPM ranges that the springs will fail to do their job - that is - force the lifter to "follow" the cam lobe and at the same time allow the valve to close properly.

[Ken A.]

Re: 1954 Carb popping

Pull the valve cover & check for a broken valve spring. If OK run a compression check. Sometimes you can reseat a valve with a good "whack"
using a brass hammer.

[Ted K.]

Re: 1954 Carb popping

Good information. Going to be out of the loop for a few days, but will let you know what I find.
Thanks