Holley 4150 vacuum

[Jeremy Hedges]

I have a 65 350hp withe the holley 4150, I have rebuilt the carb, and it seems to run fine but I can't get the secondary to open. The vacuum mechanism to open the four barrel dosen't seem to work, even at full throttle. Is there an adjustment for this? Where does the secondary get a vacuum from to open the four barrel. Any help
thanks

[Clem Z.]

Re: Holley 4150 vacuum

the vacuum to open the secondary comes from a hole in the primary venturi. as the air rushes thru the primary venturi it creates a vacuum to start to open the secondary and there is also a hole in the secondary venturi that helps pull the seconary open once it starts to open. it will not open by just gassing the engine setting still. there is a linkage on the passenger side of the carb that is the wide open stop for the secondary against the base plate. just put a small dab of grease on the baseplate where this stop hits and go for a full throttle run and see if the grease has a mark in it.

[Clem Z.]

PS

i can scan you a page from the holley catalog that shows how this works.

[G B.]

Did you install a "check ball"?

Clem has given you very good advice. If, however, you find that the secondaries really aren't opening in your road test, consider the following.

Several Holley models, including the '64-5 Corvette List #2818, did not use a "check ball" in the vacuum passage to the secondary diaphragm. (Actually, this ball will only slow the opening of the secondaries on carburetors designed for it.) The 2818 does not have the necessary vacuum channel around the ball seat area. If you install a ball in a 2818 secondary diaphragm housing, it will seal tightly against the bottom of the vacuum passage. This prevents any vacuum from reaching the diaphragm.

In other words, if you put a little steel ball in the secondary diaphragm housing of an otherwise stock 2818 Holley, your secondaries will never open.

I mean no offense by suggesting you could have made this error during your rebuild. A whole lot of people do it.

[Jim T.]

Re: Holley 4150 vacuum

Some else to check manually is that the secondaries are not stuck shut. I have had this happen to my Holley recently.

[Everett Ogilvie]

Re: Did you install a "check ball"?

And the purpose of the check ball on carbs that ARE designed to use it, is to help the secondaries close more quickly when getting out of the throttle, right? I think that is what I recall from the Holley book. On these carbs if you remove the ball, what are the consequences?

[Clem Z.]

Re: Did you install a "check ball"?

they also require more vacuum to start to open the secondary so it starts to open later to prevent a bog. they seem to be used in the smaller venturi carbs and that could be because the smaller venturi creates higher vacuum sooner and with out the ball to delay the secondary opening there would be a bog. this is JMHO nothing to back it up.

[John H.]

Re: Holley 4150 vacuum

Also make sure you installed the tiny circular cork gasket between the secondary diaphragm housing and the main body - this seals the joint in the secondary vacuum passage between the two parts.

[Clem Z.]

Re: Holley 4150 vacuum

john i just finished a #1850 holley carb and had a genuine holley kit and those gaskets plus several other gaskets were missing. good thing i buy holley gaskets in bulk so i had extras. i emailed holley about the problem and they said they would look into it. clem