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Discussion Starter #1
I just read Johnpro's post regarding finding his missing HP due to his secondaries
not opening from too little throttle travel. I just went out and checked mine and now I'm
confused. I have a 1406 too and as I look into the throat of the secondaries, I can see the
blades mostly closed. But even when I open the throttle linkage as far as it will go,
I don't see those blades moving. (Johnpro, how did you tell when your secondaries
were opening?)

The Edelbrock manual says that the secondaries open at about 65% of the mains,
but it doesn't say how. I don't see any linkage and it appears these are not
vacuum secondaries. I suspect my throttle linkage isn't right (I'll have to check
that in the AM with SWMBO in the car to be sure), but I need to understand
how this setup works.
 

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Discussion Starter #2
Follow-up.

I discovered that what I thought were the secondary blades are really the
counter-weighted air valve which opens when there's enough air moving
over it. But looking past this I can see the actual secondary blades, and
they are barely moving, and certainly not really opening, no matter
how I manipulate the throttle linkage. Can this be right? Is there some
way I can verify the secondaries are opening under actual operation
(other than strapping a moron under the hood while I do WOT blasts
up and down my street)?
 

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You will feel a burst of power, not quite like a quadrajet, but still it will be a kick in the pants.

I had a similar problem on mine with a 1405. Turned out the carb gasket I was using was just a hair too small in the port going into the manifold. The butter fly caught on the edge and wasn't fully opening. Boy that was a 50 hp gain just fixing that problem!
 

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Rich, I already responded to your PM, but will post it here as well, for the benefit of others. I'd hate to see other people driving around with fancy 2 barrels, like I did for a year /forums/images/icons/wink.gif.

Rich,
There's 2 things to look at, and 2 "gottchas". Gotchas first: First, there is a air valve above the secondaries. You cannot see the secondary butterfly without pushing open the air valves, which just look like another secondary butterfly. The other gotcha is that you can't do any of this with a cold engine. The secondaries, as I discovered on both mine and my son's '65, will not open at all with a cold engine. You need to warm it up a little first.

The 2 things to look for is the secondaries opening below the "forced open" air valve butterfly. The other thing, and IMHO, the way more important thing is to look at the secondary butterfly stop on the passenger side. If you look at the linkage on the passenger side, you'll see a "tab" on the secondary butterfly rod. As the carb gets to WOT, this tab will come around and contact a stop on the base of the carb. If this isn't comming in contact, you're not opening the secondaries all the way.

I could have the stop come around and hit the carb base if I operated it by hand under the hood. But having a helper put the "pedal to the medal" (engine off of course ), I could see that IF the secondaries were opening, it was just barely. I ended up getting almost another 1/2" inch of travel on my car, and even more than that on my son's.

The way I got the extra movement I needed, was to just put a breaker bar (it's one of the flat ones that has a notch in the end for pulling nails) against the throttle rod just above where the small "wire rod" screws into it at the top. I just shoved with a lot of force toward the firewall, and bent it the 1/2" - 3/4" I needed. You cannot tell that the rod was bent from looking at it.

The car is downright scary now. I'm sure I just picked up another 40 hp, as I basically just had a 2 barrel before.

Hope this helps some, feel free to ask more questions if you have them.

Later,
John
[/i

One thing I didn't mention ... since this is done with a warmed up engine, and you will end up giving it FULL throttle, probably several times, so don't be surprised if you flood it ... but it's well worth flooding it once, for that amazing difference if you're secondaries are not opening.
 
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