holley 4160 vacuum secondary help

[gravdigr]

My 86 blazer has a holley 4160 vacuum secondary carb the PO installed. How do you check to see if the secondaries are opening? It is only a 305 and maybe it's because I'm used to running a 350 but it feels very underpowered and I think maybe the secondaries aren't opening. My edelbrock has manual secondaries and I've never worked with the vacuum type. I'm also new to holley carbs. I tried revving it in neutral and they didn't open but maybe it needs a load?

 

[Wingnutt]

On a 4160 it's actually hard to tell by feel when the secondaries are opening when it's tuned right. You are correct about it needing a load to open correctly. About the only two ways I know of to tell when they are opening short of having a person sit in the engine compartment and watching it are to remove the air filter assembly and listen closely when you floor it. Or you can purchase a set of secondary tuning springs and start with the weakest and try each one until you can't tell when the secondaries are opening then go back down one. But you should be able to hear them opening starting at about 1500-1800 rpm or so with the air filter off.

 

[m j]

actually you should never be able to feel the secondaries opening
if you do, they are opening too fast and what you feel is a bog

 

[gravdigr]

Hmm, OK. On my edelbrock 1407 I can hear and feel the secondaries open. It's a kick in the pants, but maybe it's because they are manual secondaries. I'll try with the air cleaner off and see if I can hear anything.

 

[pauly383]

[ QUOTE ]
It is only a 305 and maybe it's because I'm used to running a 350 but it feels very underpowered

[/ QUOTE ]

Your gearing will make a difference too. I still have my 305 (383's cost a LOT) and I can hear it open when I really get on it , but thats about it. I can even hear it when underhood flooring it but it takes a lot of rpm. If you have highway gears it will be slower until you get rolling /forums/images/graemlins/k5.gif