New carb socket fits loose

I have not yet figured out the problem. I need to take my drip tray back off and remove the doubler plate and redo the fuel tank sealant between there. My best theory at this time is that maybe I put it on too thick and the clamping I used maybe allowed inner areas to get squished less than the outer areas where the clamps were contacting, and maybe that's bowing the socket outward a bit, making it fit looser around the carb. Not sure. I'll definitely update this thread when I figure anything new out.

Kelsie, I guess I’m not understanding what you’re up against (not your fault!) If you remove the air box, mount the new socket to the intake manifold, then the carburetor to the socket, tighten the socket clamp, the carb still rotated easily with light finger pressure? Can you post some pictures showing your setup? That may allow others to visualize the issue. 
Another thought, if your aircraft is certified as a SLSA and this problem is not already addressed in current technical data for your aircraft, isn’t it up to the manufacturer of your aircraft to provide you with approved instructions as to how to repair this problem? Have you reached out on the Vans forum?

Jim Isaacs wrote:

Kelsie, I guess I’m not understanding what you’re up against (not your fault!) If you remove the air box, mount the new socket to the intake manifold, then the carburetor to the socket, tighten the socket clamp, the carb still rotated easily with light finger pressure? Can you post some pictures showing your setup? That may allow others to visualize the issue. 
Another thought, if your aircraft is certified as a SLSA and this problem is not already addressed in current technical data for your aircraft, isn’t it up to the manufacturer of your aircraft to provide you with approved instructions as to how to repair this problem? Have you reached out on the Vans forum?

The RV-12 uses the conical K&N air filters, one per carburetor, rather than an airbox. But your description is exactly what I am describing otherwise. I have attached a picture of the setup without the carburetor attached so that you can see better. This is a stock setup per the kit assembly instructions from Vans. The fuel tank sealant and small bit of fuel hose at the bottom of the drip trays is a vibration dampener, and is also according to Vans' kit assembly instructions. 

There is an o-ring in the circular channel on the manifold which creates a seal against the doubler plate on the back side of the drip tray. The doubler has a large hole in the center for the intake airflow, and two smaller holes for the carburetor socket bolts on the sides. The doubler is bonded to the back of the drip tray with fuel tank sealant, per Vans' kit assembly instructions. The drip tray itself also has the same large hole for the intake airflow and the two smaller holes for the carburetor socket bolts. The carburetor socket sits directly up against the drip tray front side and the bolts run through the assembly into the intake manifold.

With the carburetor mounted into this assembly, and the clamp tightened down to the spacer, the carburetor on the 2/4 side can indeed still be rotated with a single finger with moderate pressure. The carburetor on the 1/3 side, with the exact same setup, cannot be rotated with even a whole hand of heavy pressure. The carburetor from the 1/3 side inserted into the 2/4 socket is exactly as loose as the 2/4 carburetor inserted into the 2/4 side. Both carburetors measure the same size diameter on the intake side with a vernier micrometer. Thus I have concluded the issue is not the carburetor itself.

I have also ruled out the socket as I have replaced it multiple times now, always with the same result. I also have used a socket that was hand tested by Dean at Lockwood before sending to me, and I had the exact same issue with it. So I have concluded that the issue is not the socket itself.

The two remaining possibilities that I can think of are that the manifold mating surface is warped, or that my drip tray is the problem. I just built this drip tray to replace a cracked one, so the most likely answer is that the issue is with the drip tray. Since there is fuel tank sealant between the doubler and the main tray, and since I used clamps to squish them together, I suspect uneven clamping pressure may be the cause for uneven spread of the sealant.

I hope the attached pictures help clarify things a bit. Thanks.

The only plausible explanation is the one you currently suggest.  I believe your drip tray is creating a slightly bowed mounting surface for the socket, and thus distorting the socket. With the socket bowed, you are getting limited contact with the circumference of the carb throat. Thats probably why the VANS instructions call for a “very thin layer” of sealant.  

Jeff Blakeslee wrote:

The only plausible explanation is the one you currently suggest.  I believe your drip tray is creating a slightly bowed mounting surface for the socket, and thus distorting the socket. With the socket bowed, you are getting limited contact with the circumference of the carb throat. Thats probably why the VANS instructions call for a “very thin layer” of sealant.  

Another plausible explanation is that the manifold is warped. The engine is known to have overheated before I owned it. However, I do think that the drip tray as you've described here is the much more likely explanation.

I'll update this thread when I know more.