If the helicoil is below the top surface, that should be fine. Is there a plastic spacer plate between the carb and manifold? The holes in the spacer plate could be made slightly larger, to ensure it fits nice and flat. It does seem kind of odd to have a large leak at the base of the carb. But any air leak needs to be fixed. Before worrying about how well the actual carb works, first take care of the 3 first steps of carb set up.... 1) ensure proper fuel flow and pressure, 2) ensure the ignition works and the timing is correct, 3) ensure no vacuum leaks. If all that works then it should run, even if the carb jetting is off by a couple jets sizes. Once it runs then it can be tuned.....
Typically there is a plastic spacer plate, to reduce heat getting to the carb.
In reply to TED_fiestaHP:
Sadly no room for a spacer on the Vette. It's difficult enough finding a manifold/air cleaner combo that will clear the hood.
Typically the spacer plate is less than 1/4 thick, some type of plastic, to reduce the heat transfer.
But regardless of how it's mounted can't have any air leaks around the base of the carb, but then I am sure you already know that....
You are so close to making this thing work, we all want to see you happy with the end result. At this point it should be fairly simple and the end result should be close.....
I installed a new gasket & gave it a thin coat of oil/fuel resistant sealant. The top gasket is the one I originally used. I chose it because I thought with my dual-plane manifold it would seal the carb from each side. However, it's a very thin gasket - literally index card thin - so I chose the bottom gasket to replace it.
Did I make the right choice? IDK, but it started, and after bumping the idle speed up 1/2-turn seemed to idle smoothly without any Hoover-like whining.
I took it for a short drive around the block, there's still some occasional slight hesitation, but it didn't die at stops. Hopefully the vacuum leak doesn't return. I'm calling it a temporary victory at least. 
I really need to figure out what's up with the throttle though. It takes about 10lbs of pressure on the accelerator to get any movement, and only slightly loosens up about 1/2-way down. I'm using 2 return springs, as that seems to be mandated by most sanctioning bodies, but the cable moves freely unloaded. I also lubed the cable from the carb end, and lubed the throttle shaft. And ideas to help improve it?
Where is the stud on the carb ebd? At some point its a simple lever problem....
In reply to Dusterbd13:
Here's the current location. I'm not sure if any of the other holes are really an option?
There is a hole directly above where your stud is now. That will provide more mechanical advantage, thereby making pedal effort easier.
However, that may berkeley with the ratio for the tv linkage. Check with holley.
Other option is to change the rear location of the throttle springs. Change to big hole on top should lessen effort as well.
In reply to Dusterbd13:
You're correct, the TV bracket needs to remain in that location. I'll check if I can possibly modify it to gain enough clearance to put the stud in the top hole.
Would it work any differently if you connected the springs a different way? Maybe connect at the top cable and then run them to the left? Or maybe you have to much initial spring tension... Just something to try, the spring may have to much initial leverage.. If you move the linkage by hand, how does it feel?
slip the springs off and work the throttle, if its easy then hook them to the top hole and to the front as DB said,Those look like some nice Stout Springs so that is likely it,And or try it with just the Large spring there at the house to check effort.
If I run the springs forward from the top of the throttle lever, what should I attach the other end to? Is there a typical method most people use?
I bend up a tab with rwo holes. On for mounting under an intake bolt, one for the spring.
What dusterbd said- put the throttle cable in that big top hole. I don't believe that will berkeley with the TV linkage- you're not changing how that moves, the ratio of the carb arm to the trans should be the same if you keep that in the same hole.
And obviously verify that the linkage/butterflys aren't binding on anything or interfering with the air cleaner lid (if you have a wicked drop base one) and that the linkage moves freely without the cable attached.
edit: I used my eyes- the linkage obviously isn't hitting that air cleaner. Skip that step. ha ha ha.
Pete...doesn't the carb actually have a spring on the shaft assembly? So with 2 additional springs doesn't that give you THREE springs?
In all my years of racing never had tech saying I needed 2 auxiliary springs. All for redundancy but .....
Anyway...you seem to have some stout springs on there.
In reply to Ovid_and_Flem:
Good point, it does. I believe I read it in the Challenge rules, and I presume it's part of the NHRA ruleset, as I don't remember reading it in the SCCA Solo rules. The fact these springs were packed & appear to be concentric, and also have quite different rates, made me think they were intended to be installed together.
I'll try using them one at a time & see which one gives me the best throttle modulation.
In reply to Pete Gossett:
For some reason I think this issue was addressed in an SCCA fastback ruling..but I could be wrong. Or stupid. Or both.
the butterfly's (throttle plates) are Off center to Facilitate closing If the Throttle cable were to break. A lite spring is all that is needed to over come the foot feed drag(or pull) but two are in case of OOp's.
I did a bit of CAD work tonight.
I need a blockoff plate for the radio opening, and place to mount my toggle switches. I found a scrap piece of diamond-plate aluminum, so I'll use it, but it's getting painted black to match the interior plastics.
I got the switch/blockoff plate cut out, bent, & trimmed.
I actually got the holes drilled and a coat of paint on it too, but no pics yet.
I took the car out for a short drive again & tried laying tinto the throttle a bit, but it completely bogs at anything approaching/beyond 1/2-throttle? Any ideas what might be causing that?
In reply to Pete Gossett:
Not enough accelerator pump shot,
Or
Vacuum advance attached to manifold vacuum rather than ported vacuum.
In reply to AngryCorvair:
The vacuum advance is connected to the angled port under the front bowl of the carb. Is that the correct one?
Either accelerator pump, or main jets to small. Running tad lean then goes flat when accelerating...
Which vacuum source to the advance can works better is debated and supposedly varies from engine to engine (has to do with the mechanical advance curve IIRC), but in my limited experience moving the hose from manifold to timed/ported really woke the car up.
In reply to BrokenYugo:
I switched to the timed port up top, but no change on performance. By the time I got back around the block I could hear a vacuum leak, and discovered the mounting bolts had worked loose a bit - I may end up using some Loctite on them eventually.
I had another thought though - I hadn't considered that my carb has a vacuum secondary. If it wasn't opening/working correctly, could it cause the problem I'm having?
Always more than one possible solution, I would run without the vacuum advance. Just run the mechanical advance, figure a total advance of about 35 deg. Should see full advance by about 3,000 RPM. Sometimes the Vacuum is actually retard, which allows more no load advance, then under load or acceleration the vacuum reduces the timing a little. Just running the mechanical advance is a little simpler.
