Secondary Diaphragm check ball

One more Holley question today for the experts.

I took apart the 750cfm Holley 4160 that we have on our BFN last weekend and attempted to address the on/off nature of the secondaries. When I rebuilt the carb, I installed the lightest spring in there to make sure we could pull them open all the way. Turns out that wasnt a concern, as they ended up acting like a light switch and we couldnt hold speeds between 45 and 50mph.

I went 2 steps heavier on the spring as a starting point, and put on a quick spring change kit to assist in further changes, if necessary. Should be a good starting point.

What I noticed upon reassembly is that we do not have a ball in the actuation circuit. Here is where one would go (picture stolen from the web):



I do not know if there was ever one in there. Its possible I lost it when I had the carb apart last time, but who knows. I searched the web and called Holley- they said there are 2 standard configurations:

1. Brass insert (reducer) installed in this passage, no ball.

2. No brass insert installed, ball should be present.

He said that since ours does not have the brass reducer, it should have a ball in there. The purpose of the ball (or brass reducer in the other configuration) is to slow down the actuation of the secondaries... which is the symptom Im battling.

So, I took apart 6 more spare carbs that I had to see if I could confirm the presence of that ball. 5 had the brass reducer installed, and the other had no brass insert and no ball. Ive had that carb apart before, so its possible I lost that one when rebuilding too, I suppose...

Since I had no ball to steal, the 750cfm went back together without it. Still, I could swap over a housing with the brass reducer if that would help with the issue, or track down a ball to install in this one. Can anyone positively confirm that the ball should be present in a marine carb? The Holley Tech was speaking off the top of his head and not from a parts book, so I'd like to be sure he was right.

Anyone know if the ball vs. brass insert performs differently?

I had a ball in the last 4010 I took apart.     4010, not a 4160.


But it was a marine carb.   I remember chasing the ball down, twice, on hardwood flooring.

Tim I don't have anything constructive regarding the difference between the two designs.

however, the HO 454s had these carbs from the factory, the 9022 List. Mech secondaries and manual chokes wired open.

http://www.holley.com/0-9022.asp

I'm damn curious how your boat will run with one!

Forgot you did those mods! Yes, should be close!

In the three boats I dove that had those, an 83, 84 and 85, they worked quite well.

Sounds like you're close to a solution

Tim,

I know that my 650CFM 4160 has a ball. I've never tried running it without it to see what happens and I also have the lightest spring Holley makes in there with the quick change spring housing.

Everything I've read says that if you don't have the ball or the reducer, the secondaries will just flop open and you'll experience the symptoms that you have now just as the tech told you.

I gotta believe that a ball should be in there and will solve your problem.

Eddie, great datapoint- thanks! I'll pull a secondary housing with the brass insert off a spare carb tonight.

CQ, at least I had them at one point... better than you can say!

I swapped out my housing (which was missing the check ball) for another I had on hand that had the brass insert pressed in. Combined with a slightly heavier (3rd lightest) spring, secondary actuation is now 100% better. They transition as slow as I want them to, and have no problem holding any speeds that were previously problematic (45-50mph). Still getting full secondary actuation based on the new top end speed as well.

Tim, check CL, maybe you will get lucky and find a 1150 Dominator for that beast!

I put in the metering block with replaceable jets... though I havent messed with the jetting yet. I have it jetted equivalent to the plate for the time being, which should be on the rich (safe) side.

I do believe there is some room to improve performance slightly by leaning them out a bit... Holleys tend to be jetted pretty fat from the factory. Rich = safe. Alan probably did the most work with dialing in the jetting on his '81. Rather than rely on the classic plug chop method, he actually ran an O2 sensor and was making adjustments based on his A/F ratio. I believe he ended up a few jet sizes smaller than stock on his highly modified 351w that spun 5500 or higher depending on which prop he had on.

On our BFN, we have a high enough compression ratio (10:1) and an aggressive enough cam that I'd rather err on the safe side for now... if someone edges us out at some point, maybe we'll revisit that, ha.