A friend of mine has a 52' coupe with a 230 and overdrive unit, he spent the better part of a year chasing the "percolation" thing nothing seemed to work, (this guy is no dummy ether) ended up separating the manifolds by removing as much material as possible were they bolt together and making block off plates to "cap" them and put some insulating material in between the two caps,I would not have noticed the mod except for the insulation, worked out just fine. He's been driving the coupe for about 30 years did the mod 20 years ago. That's some nice work Don!!!