Heat riser bushing gone.

Back when I was tinkering with the 2bbl (Super Six) set-up ,I had the same problem.Ended up taking the heat riser out and tapping/bolting the holes shut.The car would just take a couple minutes longer to warm up.Alot of people remove the heat riser.

Here is a company wherte you can buy a new replacement exh manifold.

www.1aauto.com

$110.00