SO like here's the run through.

Its a 4160 that has been converted over to a metering block.

74 jets in front (perfect dead on cruise jet as per my O2 sensor)
81's in rear (have no idea since i have a little issue)
white accelerator pump cam on 2nd hole
31 squirter

vacuum secondaries with a quick change spring housing and a purple spring (one level easier to open then the stock 'plain' spring)

OK. my secondaries don't open. I diconnected them from the diaphram and drove around and the performance was the same. I replaced the diaphram itself and installed that quick change spring top and still they don't open.

I know the diaphram is good because you can suck on the top of the vacuum housing now because there is a big hole that gets covered by a top plate....so if i leave the top plate off and just suck on it a little, the diaphram does as it should and the secondaries open.....car off of course heh.

THe seal between the vacumm diaphram housing and the carb is brand new cork one that came with the secondary quick change spring top.

logically, i must not be getting a vacuum signal to the diaphram...

It has a check ball which is installed....

any thoughts?

 

Need more info:

Carb size, engine size, engine mods (exhaust, cam, heads, intake, etc.).

(I edited the subject line for you to indicate a VS rather than DP carb.)

 

More info coming right up... i just figured it probably wasn't necessary since i'm thinking there is some sort of blockage or issue with the carburetor rather than anything else and was hoping this might be a semi-common thing.

750 cfm carb

14 mmHG vacuum at idle

350 engine
protopline 180 cc intake runner heads
224/224 .528/.528 @ .050 cam
Vic Jr intake
8.6:1 compression


shorty headers and 3inch exhaust

 

It's important because a 350 won't start opening the secondaries until about 3500 RPMs. It probably won't fully open them.

Try putting a paper clip on the secondary rod, right at the bottom of the secondary vacuum housing. Take a full throttle to redline run, and see if the paper clip has moved down. If it has, that's how much the secondaries have opened. Change to a lighter spring, rerun the test, see if they open more.

In a properly tuned VS carb, you won't feel the secondaries open.

 

thanks i will try that.

however, as far as i can tell, there is no performance difference between having the secondaries disconnected and attached at any WOT run.

i'll go do that now and get back to you about it shortly.

thanks