Need some opinions, have 91 502 mags, had original housings-2hoses to each manifold, went to 496 ex manifolds couple years ago took the two for each manifold and y'ed them to 1 ran it in the bottom of manifolds worked fine, now want to change to newer style merc housing with only two outlets 1 for each manifold- when I look inside I can see water can only flow to manifolds when thermostat is open my question do I just drill 2-3 small holes in thermostat base ring as I have read about or do I need to put a fitting in one of the avail holes in housing and use check valve etc for pressure to maintain water flow during warm up
thanks Randy

When you use that housing the thermostat fits up into the housing and is held in place by a plastic cup. It does not sit in the intake like you might be thinking, so water is always flowing to the exhaust.

If you take a look @ some middle 90's schematics it should be clearer than my description. Here's a link

I believe that may also use a "by pass" thermostat housing like the ones used on crossover systems. You would plumb the by pass hose from the water circulating pump to the thermostat housing which would then feed out to the two hoses feeding the manifolds, (one hose to each manifold).

Cliff

The housings with only 2 outlets have an internal bypass that keeps water flowing to the exhaust.

Thanks Guys upon further looking in holes it does connect