Hello all! This site is amazing. I'm wondering if I can get some advice.

I've got a 67 C10 short box I'm driving and building at the same time. I've completely rebuilt the suspension, installed a T5 trans, rewired just about everything, installed power disc brakes up front, and I'm in the midst of dropping a Holley 390 on a Pontiac OHC intake. Everything has worked brilliant up until now.

It's all together, and idled when I first dropped it on. Now it starts under choke, idles very high, then stalls. (feels like the float bowls draining). Sounds to me like a vacuum leak, but I can't find the leak. I'm still a rookie at most of this stuff.

Let me take you back to where the problems started. The Pontiac bolt holes don't line up with the chev, so I used a gasket as a template, drilled and notched new mounting holes in the manifold. It seems to mesh well with the chev 250 stock exhaust (exhaust heat riser is blocked off).

The carb sits on an edelbrock adapter, and sits 90 degrees to the block so that the primarys match up with the Qjet primary inlets on the intake. Fibre gaskets on top and bottom of the adapter.

The heat riser on the intake looked like a huge spot where a vacuum leak could occur, so I used silicone (permatex gasket maker) to seal it up around the inlet holes. This was in attempt to fix the vacuum leak, but didn't make any difference.

Here's what I've got for hoses:
1)Fuel line extended to wrap around to the Holley
2)Vacuum advance from the distributor to the carb
3)base plate port on the holley plugged
4)PCV from valve cover to brake booster with a "T" running to the intake pcv port.

Cables:
1)Choke is a basic setup that works fine
2) Throttle cable is a Lokar cable running all the way around the carb to make up for the 90 degree position of the carb.

I've RTV'd the pcv grommet, and plugged up the port on the front drivers side of the valve cover.

I've adjusted float bowls, but can't get it to idle long enough to be accurate with adjusting anything.

Everything LOOKS good, but like I said, will only start under choke, idle super high, then stall. Vacuum leak, right?

But where?

I know it's gotta be something basic I've overlooked, or maybe just give up on trying to make the OHC intake work, but I thought I'd ask the experts and it's why I'm here. I can post any requested pics of the setup if it'll help.

If it means ripping out the intake and replacing it with an offy or clifford, I'd gladly take a right hook to the ego to get my truck back on the road.

If anyone has any tips, I'd appriciate any help. I'm totally stumped.

Thanks!