Intake manifold

Pan intake manifold Tees are somewhat crude in design. Air leaks at the seals are fairly common. To combat the problem, leak testers are used with about 12 -15psi pressure. Soapy water is lathered over the seal area, carb gasket stack and adjacent area including known leak points like rocker cover screws, etc. A continuous stream of bubbles is a fail and needs addressing for proper engine behavior and health. Take care to wash the soapy residue away after testing as it rusts/corrodes some metals.
Snoop leak detection liquid is said to give superior results over soap and is available from Swagelok.

My DIY leak tester made to suit Linkert flange manifold.

A simple adjustable air regulator, gauge, push-lok fittings and air coupler