Bigger exhaust manifold for a 1Y

[caveman]

If the manifold holes were smaller, there would be a problem with the pressure differential where the column of air enters the larger chamber in the head. In our case the problem is the air getting buffeted where it touches the face of head,and tries to find it's way in. There is a reason high performance and even stock motors have those channels match.

[weldore]

hmmm...ill have to get some photos up as my inlet manifold holes are a perfect match with the bottom of the ' D ' ports but they are a full circle as opposed to being a ' D '.when the 1y gasket is placed on the 1.6 gasket there is no interferrence...ill have another look tomoz tho just to make sure