Like Bottlefed70 stated, if you pulled them open with the engine running and it didn't bog down, the fuel is flowing. No more than you can open the primaries without over revving it in neutral with no load, you can only crack the secondaries slightly and the amount of fuel they draw will not be visable. Work the throttle with the engine off, and see where, on the driver's side linkage on the carb, connecting the two sides together you can insert a machine screw and nut to convert it to mechanical operation. Do this and then drive the car, you will be guaranteed to have full secondary operation and then you will be able to "feel" if they were opening on their own without the screw. The only other way to see if they're opening is to remove the hood and drive it without the aircleaner and get a freind to watch the secondary linkage and see if they're opening. That or do it on a chassis dyno.Cobain03 said:engine off, the butterflies are closed. i have pushed them open before while the car running and it sucked air like crazy and no fuel came out.
DJCarbine said:I just swapped out my vacuum secondary spring a few minutes ago.. it was the black one, which according to the chart doesnt BEGIN to open past 4k rpm, and never fully opens. I put in the yellow spring, which begins to open around 1500, and fully opens a little past 5k i beleive. WOT, no stumbles.... I am going to try the short yellow spring later on.
Black spring FTL.
DJCarbine said:Negative, the vacuum secondary spring kit came with a manual and a chart. It estimated on a 350CI engine, at what RPM @ WOT the spring would begin opening, and also when it would fully open. It also had a chart for a 454 CI engine. I derived the approximate RPM's for a 289 engine with that info.
I should have added that the RPM's were approximated @ WOT, with the airflow and efficiency of the engines in the chart estimated at stock/normal values. The chart came in a kit for 4160 Holley carbs.
Also, vacuum source for the secondary diaphram... I am unsure if it is manifold vacuum, or ported... or perhaps some special vacuum source. The manual was very specific in adding that there were ball bearings in some model carbs secondary diaphram ports that should not be removed because they served some special purpose. I'll scan the manual later tonight if you would like
ashford said:ok here it goes vacuum secondaries 101.
lets start out with the pod. it is a vacuum diagphram with a mechanical linkage. on the top side of the diagphram there is a spring(this is also the vacuum chamber)opposite of the linkage. at rest the pod pushes the linkage out closing the throttle plates. when vacuum is applied the diagphram pulls on the linkage and compresses the spring.
next is the vacuum source for opening the secondaries. IT IS NOT MANIFOLD VACUUM. it has its own special port on the underside of the venturi. which basically utilizes bournoullis principal, air moving over a curved surface creates vacuum- more flow more vacuum(same damn thing as main metering system). so more cfm means more vacuum.
add that vacuum to the pod and you have vacuum secondaries. so the more cfm thru the primaries the more the secondaries open. put in a lighter spring and it happens earlier.
Keep your beerBottleFed70 said:Awesome! That explains alot thank you. I had always though it was manifold vacum.
D.Hearne: Your right... can't get the secondaries to open while the engine is off. I owe you a beer!
Cobain03 said:so.. more airflow = more cfm = more vaccum right?
airfilter vs no airfilter on a carb. your getting a whole lot more air which is more vaccum. that would screw things up wouldnt it?
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