early A 273 ex manifolds wont seal Help!

'65 dart drivers side 273 ex manifold on a 83 318. leaks out the bottom side on the manifold on cyl 5 & 7. I know the contact area is thin so should I ride the gasket high as it will go & WHICH gasket should I use?? thank you for your time. this will be my 4th time on this,I want this to be it PS I did plug the air injection holes.

You have to grind some of the block away. The manifold is making contact with the block. I've done this conversion several times (318 to early A-body).

I have a 84 318 in the garage that I just took out of a 66 Dart with 273 manifolds if you need a pic

What you need to grind away is part of the cylinder head where the air injection port is. I've been there, had to do it. Drop the exhaust pipe, take the manifold off and take the gasket off, then lay the manifold back up against the head. Just behind the steering column, you'll see the portion of the manifold that drops down and curves in towards the block hit the head.

Then there is the joy of reaching it with a grinder.

Good luck!

Jim Burch

Thanks guys & yes please a pic will help guide me on this.