Open or restricted riser gaskets?

[nextboat1]

Hello,
I just purchased a new set of Sierra risers and manifolds for my 5.7 with an alpha drive. My old risers had restricted gaskets. Should I use restricted gaskets again or should I use the open ones. I seem to recall reading a bulletin somewhere that said I should use the open ones. My engine serial number is 0l020702. My manifolds only have one hose each running from the thermostat housing to the bottom of the manifolds. No hoses to the risers. Thanks.

 

[Bt Doctur]

use the restricted ones if not using riser extentions. with riser extentions, open ones on the bottom and restricted ones on the top

 

[itzmepete]

use the restricted ones if not using riser extentions. with riser extentions, open ones on the bottom and restricted ones on the top

Correct answer. Although some later raw water cooled can be replaced with all open gaskets between the manifold and riser, check your engines S/N for applicability. The manual also shows all open gaskets between the manifold and riser on fresh water coolant cooled engines. The block is cooled by anti freeze coolant fresh water then raw water flows thru the heat exchanger cooling the coolant, exciting thru the manifold, and out thru risers being discharged with the exhaust. Also, I've heard on the forums there are some freshwater cooled in which he exhaust manifolds are supposedly also cooled by anti freeze coolant fresh water and the riser is the only raw water cooled implying a blocked gasket is used.
I did not see this in the manuals and im skeptical as the exhaust manifolds are extremely hot causing the coolant to get very hot and possibly overheat the engine.