do the 4 corner idle adjustable carbs use a secondary power valve . or is it blocked off
Then I have the only HP's ever built with dual power valves. Humm, go figure!Yeah I have some older 4779s that have two power valves. They all used to. I still have one I bought brand-new in 1977.
None of my HPs came equipped with secondary power valves. I've never seen an HP with a secondary power valve (and I've seen a lot of them). Holley first started adding 4-corner idle about 15 years or so ago. Carb shops had been performing the modification before that though.
I don't think any of the performance Holleys come equipped with secondary power valves anymore.
I wonder why they need to change back and forth?All right Al, here's the scoop. I called the Holley tech line (and man was I on hold for a long time to get through).
I finally got to talk to a person and asked him about the HP Series and the secondary power valve. He told me that all of the earlier HP carbs did not come equipped with a secondary power valve. It wasn't until a couple years after the dash one models came out (numbers with -1 after them) that they came with rear power valves. He says that all HPs now being manufactured have secondary power valves. So you must have a new or newer -1 model.
Like I mentioned earlier, I haven't bought a new one in a couple years now but the last one I got from Summit still did not have a secondary power valve. I usually block the secondary power valve anyway but I guess Holley got enough requests from their customers that they finally decided to offer the provision on their newer carbs. I still have a Holley HP 750 that I bought in the early 90s the day they were released for sale. I remember how excited everyone was that Holley decided to produce them.