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| Holley /Vacuum Secondary https://slantsix.org/forum/viewtopic.php?t=3463 |
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| Author: | Trysix [ Thu Apr 11, 2002 8:48 pm ] |
| Post subject: | Holley /Vacuum Secondary |
I'm running the 390cfm Holley 4bbl. How do I tell if my Vacuum Secondaries are opening? I don't think they are...I just don't feel them come on...and the throttle plates are dry and charcoal colored. Soupitup@msn.com |
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| Author: | Doc. [ Fri Apr 12, 2002 11:22 am ] |
| Post subject: | Re: Holley /Vacuum Secondary |
Quote:
: I'm running the 390cfm Holley 4bbl. : How do I tell if my Vacuum Secondaries are : opening? I don't think they are...I just : don't feel them come on...and the throttle : plates are dry and charcoal colored. Good to see that I am not the only one who has had this concern. The *best* way to check this is to get the car onto a chassis dyno and do some "pulls" while you watch. Next best is the dragstrip test. I go to a test and tune session with a handfull of the secondary springs and start tring different ones, the time clock tell the story. Here is another "trick", I mounted a microswitch onto the carb that comes-off the secondary linkage, it is wired to a small light on the dash which comes-on when the secondaries start to open. (I can also trigger my NOS system off this switch) This tells you the secondaries are open but you have to keep re-adjusting the switch's position in a "hit or miss" fashion to figure-out how far the secondaries are opening. (My current SL6 has a hard time completly opening the secondaries on the 600 cfm Holley it's running) DD |
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| Author: | Dave Clement [ Fri Apr 12, 2002 11:57 am ] |
| Post subject: | Re: Holley /Vacuum Secondary |
Quote:
: I'm running the 390cfm Holley 4bbl. : How do I tell if my Vacuum Secondaries are : opening? I don't think they are...I just : don't feel them come on...and the throttle : plates are dry and charcoal colored. If the carb is tuned properly you won't feel them opening. It is supposed to be a smooth transition. That being said; what color secondary spring are you using? The stock natural color spring is stiff (intended for a small v8) and will not allow the secondaries to start openig until quite high in the rpm range. I am using the long yellow spring which is a little to soft (I can feel the secondaries open) but I like the sensation. The purple is likely the best bet. If you follow Holley's recommendation you keep going softer until you get a bog then go up a size or two. Dave Hot-Rod 6 dave.clement@motorola.com |
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| Author: | trysix [ Sat Apr 13, 2002 8:45 am ] |
| Post subject: | Re: Holley /Vacuum Secondary |
Dave, Doc, Thanks for the quick reply. I have installed the Quick Change spring kit form Holley and have gone through the spring progression and settled on the brown spring.I have since found out that a trick way to check the travel is to put a paper clip on the diaphram rod (top next to housing) then make a run. Check to see how far the clip slid down the shaft.I Have'nt tried it yet but I'll let you know how it works.It just bugs me that I can't tell. Doc: I like the Idea of a micro switch because it gives you a constant monitoring...so that you know exactly when it opens. Also I want to try putting a screw through the safty cam on the sec plate shaft. I thing this could be adjusted to make sure they are fully open at full throttle...but experiment will tell. Thanks again I'll let you guys know what happens. Trysix/David Soupitup@msn.com |
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