I have an 82 Vette that had a coolant leak at the back of the intake manifold. When I removed the intake, there were plates on the intake gasket blocking off the rear coolant passages. The front ones were left open obviously, or the coolant could not have gotten to the thermostat. The manifold (crossfire injection) has a passage under it from the rear ports to the front and to the thermostat. This leads me to believe that the ports should be open for coolant to flow from the rear of the heads to the thermostat, and to warm the floor of the intake to assist in fuel vaporization. I have 2 questions.

1. Are the ports supposed to be open or blocked per Chevrolet?

2. If they are supposed to be open, why would someone block them off?

Thanks in advance for your input.
Gumby

 

The rear water jackets are supposed to be plugged using the special gasket set that is used for the CrossFire '82's and '84's only. That set also includes a lid gasket and is awfully expensive as compared to the sets used for earlier years. Rather than buying the '82/'84 sets I have always used plain old 1980 gasket sets then plugged the rear water jackets with common Bondo about 2" deep. Then I use Permatex Ultra Blue or Ultra Black silicon to stick the lid on. The reason those rear water jackets are plugged is because it was impossible to cast in the huge water jacket that runs under the center without having the ends open to get rid of the casting sand. And if those water jackets aren't plugged then coolant will rise up out of the rear of the heads and pass straight thru the bottom of the manifold and out of the thermostat housing while disrupting the cooling in the block. Every Chevrolet V8 manifold ever produced had the rear water jackets plugged except for the CrossFires because of the "getting rid of core sand" problem. But rather than using your CrossFire manifold over again I suggest you buy a Renegade from DCS in Arizona. The original CrossFire manifolds will only flow around 425 cfm but the Renegade will easily top 700 cfm.