This plug fits the intake manifold, exhaust crossover on the bottom of a 1957-1961 Buick 364 nailhead engine with a 2 or 4 barrel stock intake manifold.
For an easy installation, insert the plug into the bottom of the manifold and hit the center with a hammer, this will flatten and expand the plug for a secure fit.
If you have the Buick 401/425 Engine and require the 2" plug, please click this link here.