Thread: Vac secondary test?

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What can I do to check if my secondaries are opening??? Carb is holley 750vac model 4160. Thanks.

That sounds good. I already have a lighter spring in there. I'm just not sure if they're opening at all! After a WOT run, the plugs are clean and white, showing a lean condition. I don't really feel a power surge, more of just a gradual increase of RPM. I've tried bigger jets-no dice. Plugs always come back the same. Is there anyway to ensure the secondaries are opening other than strapping it to a dyno and watching?????

Thanks for the help guys/gals.

-KevD

Go down the road about 10-20 mph then floor it!Be safe about it though!come up to speed and,let completly off of the gas as fast as you can.When you do this you will hear a big "woosh". This will be the secondaries closing.The best way to really adjust it,is to take it to the track and pay attention to your times,and MPH.I started with a weak spring and changed springs until ,my et,mph got it best.When my mph and et started to fall after peaking,I went back to the spring I put in just before.They sell a kit of a few springs(color coated) for I think less then ten dollars.Theres also a little red book holley sells.This thing is a Holley " bible" .Theres another that has more ibfo and tricks ,but I forget the writer.There is also plenty of pics. to help get a better idea of tuning your holley.

I used to modify the linkage, bend 16 d nails weld them on the linckage so I had a mechinical kick in.

This book is a good source of information