holley street avenger vac secondaries never open

[willard]

I have a 770 holley street avenger carb on my 383 with #60302 lunati cam, stock intake/exhaust. While the engine responds nicely I see that the secondaries never open (checked with a paper clip, while accelerating under load). I checked the diaphragm, the linkage, the spring (silver one) and everything seems to be ok. Carb is brand new out of the box (now has about 300 miles).
Maybe the carb is too big and the engine doesn't make enough airflow?

[Hemi Dude]

I can assure you your 770 is no way too big for your engine. A healty 383 can flow well over 800 cfm air at 6000 rpm under full throttle. You will never be able to determine correctly with vacuum secondary carbies if your secondaries open or not unless you are at full throttle under load accelerating. The safest way to do this is on a chassis dyno, or at the track. If you can find a performance shop that has such a dyno you can stand next to your car and watch yourself while someone else driving it on the rollers. While you are there they can monitor correct air/fuel ratio and adjust ignition timing properly at the same time. The whole exercise should not cost you more than $200. It is money well spent to prevent an expensive engine overhaul.

Good luck
Hemi Dude 

[CUDA JAS]

I have a 770 holley street avenger carb on my 383 with #60302 lunati cam, stock intake/exhaust. While the engine responds nicely I see that the secondaries never open (checked with a paper clip, while accelerating under load). I checked the diaphragm, the linkage, the spring (silver one) and everything seems to be ok. Carb is brand new out of the box (now has about 300 miles).
Maybe the carb is too big and the engine doesn't make enough airflow?

Is the silver spring the lightest spring?

If not, pull the spring and put in a lighter one untill they open.

[willard]

The silver one is mid-light one, I tried with another, very soft one but it did not work.
I made several 1/8-1/4 mile passes at WOT and I think that the secondaries should open in these circumstances.
As the vacuum passages are not clogged, throttle blades move freely the last thing that came to my mind was overcarburating...

[moper]

IMO, it is too large. Plus, as I said in your other post.. the engine seems down on power and the cylinder pressures are a little low. VS carbs work on air flow thru the carb to get the secondaries open. If they dont want to, you either dont have enough air flowing to open them, or the spring is too stiff. They use Holley springs too, I would put in the purple for starters and see how that works.

[heminut]

I agree with Hemi Dude, the carb is not too big. I've got a Holley 3310 (750 vac. sec.) on my 5.7 hemi (345 C.I.) and it works great!

[Chryco Psycho]

there is no way it should be too big , the only thing I can think of is if the vacuum passage is blocked or leaking from lack of seal between it & the body or if the ball inside the vacuum pot is blocking vacuum flow , try removing the ball