You might try putting a nylock nut on the 1/4" stud, before you put the scoop on. That will allow the scoop to be trapped between it and the wingnut, and not tighten against the filter. I use nylocks under the scoop on both of my cars, and never have issues with loosening.
If that doesn't do it, then you can make a brace from a piece of aluminum and mount it to the rear bottom of the scoop. Then run it down to one of the carb base studs, and add a 2nd nut to clamp the brace.

 

Not entirely sure I follow Vall. You're saying put a nylock on the stud, then tighten the wingnut against that? I'm also not sure if this scoop is the same as the hilborn style's you're using. Here's a pic of what this setup looks like sans scoop. The scoop itself just screws onto that small plate underneath the filter element. There's another piece that screws onto the bottom front of the scoop (in pic) and the wing nut holds the entire thing in place. I don't know if that's the same as yours. I'm going to take it for a quick ride so I can try and get a clip of the WOT bogging. I just started the engine for the first time since the new fuel pump and another set of plugs. Same vacuum readings as before, not sure what I was thinking might change it but was still hoping. I hooked up the new 2" vacuum gauge I bought to mount inside and got a reading of about 6" on that one. I did notice that as soon as the rpms get just over 1000, the gauge was reading 11-12" hg. If you could try and clarify from these pics about the nylock and wingnut, I'd appreciate that very much sir. Hope to have that clip on here this evening also.

 

Here's the clip. Only tried it from a gradual WOT, usually doesn't spit like it did the second time, but still bogging. Everything else is working fine from what I can tell.


http://vid1298.photobucket.com/album...psxa13xyi4.mp4

 

I do not feel like that is a lean condition strictly going off how my car runs. Do you have a larger air cleaner you can try? My 350 wouldn't run when i had a 10" or so K&N round filter, it wasn't until i put the K&N filter top on it that it would run right. Could be a similar problem?

 

Seems to me it's nosing over about the time the secondaries are trying to open. It's likely starving for fuel for some reason? I'd look at float levels, and also at fuel pressure. Another thing to consider is distributor advance. If it's rpm related, it might not be advancing properly, if it always stumbles at the same engine rpm.

You're correct on the scoop. It is different, but not very much. Since yours is retained the same way as mine, it needs to be fixed the same way. First make sure you have a lock nut on the 1/4" stud that locks it against the carb. Tighten it snugly down where it screws into the carb's air horn. That will keep the stud from turning. Then put another nut under the air cleaner top. Set the height on that nut so the top tightens against the air cleaner element, but doesn't compress it so much. Then when the chrome air cleaner top is installed, it will be sandwiched between the nut and the wing nut. Should hold the scoop from turning easily.

 

Thanks Vall, I understand what you mean now about the lock nuts. I'll work on that today. Appreciate the tip! Sudstoy, I do have a 14" air cleaner, but no element for it right now. This is the small element that comes with the shotgun scoop and I don't like it at all. That was my very first thought when I realized there were issues with WOT weeks ago. I don't know if that's what's causing the problems but I agree with you, it's not staying on there much longer.


I'm thinking that the bogging has something to do with these Air Valve Secondaries and the adjustment flap on top. This Thunder Series carb is different than the 600 Performer carb that I used to have on this engine. I'm going to experiment with adjusting that flap tighter/looser today and see if that helps. I read last night about that flap and from what I understand, it essentially chokes the secondary to provide vacuum to draw fuel through the jets. The tighter it is, the more vacuum and fuel, the looser, you get less etc. Going to call Edelbrock and talk to someone there first. I most likely need weaker step up springs for the metering rods also since idle vacuum is so low they aren't being kept in the up position, but that's something different from the secondary issue it's most likely having. Of course it's raining again today, hopefully it'll let up so I can try and get this sorted out, TODAY.

 

With engine off, have you looked down the carb while working the throttle linkage to make sure the secondaries are opening all the way? Does your carb have a choke linkage/secondary interlock like the Quadrajets have, and that it's working right?

 

I haven't done that with the engine off Chuck. Forgive my ignorance but I wasn't sure they would even do that being they're not mechanical secondaries but rather this air valve deal. Maybe that makes no difference, I don't know sir. They seem to work fine not under load however. WOT works fine while in park and working the throttle with my hand so I would have to say they are operational, just not under load. The carb has an air flap over the secondaries that is adjustable. I don't believe it is the same as a Quadrajet. I talked to Edelbrock and was told to try and tighten the flap one full turn at a time to see if that helps. That's what I'm going to try today now that the weather is nice. Hopefully I can get it working properly and get a better video clip to share!

 

Been working on this WOT deal and it's still giving me fits. With the engine off I checked and the secondaries do open with the throttle. They don't appear to open extremely far with the engine off, is that due to them being vacuum operated? They don't open to the point where they are vertical to the carb base. I started the engine and worked the throttle to the point where the secondaries start to open and got a pop through the carb with a bit of fire. That sort of turned me off to trying to put my face over top of the carb to see if they were opening all the way. I got the blue springs for the metering rods today and put them in there. Throttle response is great, have noticed no lean spots at cruise mode and power mode at all while driving. It's only when the secondaries start to open. Tightened the air flap per Edelbrock's instructions one full turn, twice now with no beneficial change. Timing is still set and advancing properly (just finished checking again with the light.) Fuel pressure good also. Guess I'll get back on the phone with Edelbrock.

 

Correct me if I'm wrong, but aren't your secondary throttle blades (in the base plate) mechanical and when working it with engine not running, supposed to be wide open when the primaries are fully open? At least, that's how the manual describes it. Then you have counter-weighted secondary air valves above the throttle blades, as well as the adjustable secondary air flap at the top.