Inside the vacuum secondaries' diaphram housing is the port which transmits the vacuum signal from the main carb to the diaphram which activates the secondaries. Most books on Holleys I've read and instruction sheets from Holley which accompany their secondaries spring kit distinctly say to NOT remove the check ball or the action of the secondaries will be too abrupt in opening or closing. Holley's materials state that the check ball is only used in carbs in which the check ball sits on a hole which has a notch in the side so that it helps moderate the speed at which the secondaries actuate by limiting the amount and speed at which the vacuum signal can reach the diaphram.

Many years ago I removed the check ball under the advice of hot rodding friends of mine and I saw no real change in peformance. When I restored the car the 2nd time, I added the check ball back in and saw no real change in performance.

My favorite Holley book has great illustrations which show the check ball and describe how it functions but doesn't necessarily caution against removing it.

HOWEVER, while breezing through my Chevy shop manuals, all three of the ones I have which cover the carb (Chassis Service Manual, Overhaul Manual and a supplemental manual for the 396 and TH-400 transmission) show the secondaries vacuum pod in an exploded view which does NOT include the check ball. Also, the written instructions make absolutely no mention of the check ball. I wonder if Chevrolet versions of the Holley carbs just didn't use the check ball at all? But, given my own experience I don't think having or not having the check ball really makes as much difference as Holley shouts about in their own documents.

Its a trial and error thing. I have removed the check ball on some cars and it has created a huge bog, simply because the vacuum secondaries are just plane flopping open. On other cars I have removed and it really helped it out. So try it without and see.

Dave

I can tell you that you will notice the checkball is missing if you use of any the lighter secondary springs.Especially if you "floor it" going down the road. Hook a vacuum gauge up..and go for a ride. Remember,without it the secondaries open rather quickly instead of gradually and without a secondary accelerator pump you are not getting the fuel out of the boosters quick enough.
I have tried it before w/o the checkball and the tires get easily over powered. Doesn't mean its faster ;)

I can tell you that you will notice the checkball is missing if you use of any the lighter secondary springs.Especially if you "floor it" going down the road. Hook a vacuum gauge up..and go for a ride. Remember,without it the secondaries open rather quickly instead of gradually and without a secondary accelerator pump you are not getting the fuel out of the boosters quick enough.
I have tried it before w/o the checkball and the tires get easily over powered. Doesn't mean its faster ;)

I would think if the secondaries open too quickly you'd get a bog?

I would think if the secondaries open too quickly you'd get a bog?

not if you "roll" the throttle...and they will open quicker than w/the checkball,hence wheelspin. This is with 454+ cubes.But,if you leave the checkball in as Holley intended,you don't have to roll the throttle...just hold it to the floor and let the motor open the secondaries. Leaving the checkball out is more of a "seat of the pants" fun factor IMHO and experience. I prefer to leave it in there.

I got the bog w/o it, even with the heaviest spring install to try and compensate. This was a 870 carb though.

I got the bog w/o it, even with the heaviest spring install to try and compensate. This was a 870 carb though.

..doesn't noticeably bog when you have an automatic/high stall :D

I guess I'll leave it in there, it doesn't seem to make much difference either way in my experience. I just wonder why the GM manuals all make no mention of the check ball.

If you don't notice any difference,the secondary spring is too stiff or you are not achieving wide open throttle. What size cab are you experiencing this with?

This is the 4150 on the L79, it's rated at 585cfm. For a high winding 327 it's probably on the small side but with peak power at 5800 it does just fine through 6000. I think I have the second softest spring in there now. It worked great with the standard spring and a paper filter but when I switched to a K&N filter I had to go to a much softer spring to get the correct secondaries function.

In the past when I had removed the check ball I was still running the stiffer spring and a paper filter, I've always had the check ball in there with the softer spring and K&N. In the past, (stiffer spring, paper filter) it ran just the same with the check ball in there or not. I might notice a difference now with the softer spring, but I'm currently out of those tiny little cork gaskets that seal the vacuum can to the carb body so I can't go playing with it. I've had a dickens of a time finding a way to buy just those little gaskets by themselves without buying a whole rebuild kit.

I did check, I am achieving WOT and I put a telltale on the secondary linkage and it is opening. I can't determine clearly how far they are opening, but it would appear they are opening at least most of the way.

I should disable the secondaries and take a spin just to know what it feels like when they DON'T open.