Holley 4160, secondary won't kick in.

[brumbach]

I recently rebuilt my holley 4160. Runs good but didn't seem to have the acceleration that it had before rebuild. I suspected the secondary wasn't kicking in. To test, I tied off the secondary to prevent from opening, drove the car and noticed no difference in performance. All appears okay with diaphram, i.e., not torn. Also vacuum port is free of obstruction. Unquestionably, the carb is only operating on two barrels. What's wrong? How do it fix? Thanks

 

[jerrybramlett]

If you have a Corvette assembly line carb model such as a List #2818, 3367, or 3810, then it doesn't use a restrictor ball in the secondary diaphragm base like most aftermarket spec Holleys. If you installed such a ball in a diaphragm vacuum passage not designed for one, then it will block venturi vacuum from opening the secondaries.

What is the Holley List number stamped into your choke horn?

 

[brumbach]

If you have a Corvette assembly line carb model such as a List #2818, 3367, or 3810, then it doesn't use a restrictor ball in the secondary diaphragm base like most aftermarket spec Holleys. If you installed such a ball in a diaphragm vacuum passage not designed for one, then it will block venturi vacuum from opening the secondaries.

What is the Holley List number stamped into your choke horn?

List number 3367. When I rebuilt it, I didn't install a restrictor ball. Seems if the diaphram is okay and is sealing, then something has to be restricting the vacuum port. What do you think?

 

[jerrybramlett]

That's possible, but not a common problem. That passage sees only clean venturi vacuum.

Did you use the little red cork gasket (between the carb main body and the secondary diaphragm housing) or a rubber o-ring? Maybe it compressed enough to squeeze the opening shut.

 

[brumbach]

Interesting you should ask. While waiting on your response, I took the secondary diaphragm off and noticed that the diaphragm housing gasket was absent. I assume I failed to install. Anyway, went back into my renew kit and used an o-ring I found. Don't know if it was the right one or not. Didn't notice what came off when rebuilding. The one I used was larger than the orfice but smaller than the impression on the diaphragm housing. Took it for another test drive. Seemed to accelerate a little better but not quite what I'd expect at full throttle. Was I suppose to have used a red cork gasket? The only unused cork gasket remaining in the kit after rebuild is sort of brownish-black, a lot thicker than the rubber o-ring and looks like it would have to be inserted into the orfice as opposed to surrounding the orfice. Hope I'm not confusing...

That's possible, but not a common problem. That passage sees only clean venturi vacuum.

Did you use the little red cork gasket (between the carb main body and the secondary diaphragm housing) or a rubber o-ring? Maybe it compressed enough to squeeze the opening shut.