[seattle gmc]

I'm wondering how you have it hooked up? I bought a katz 800 watt heater this summer, and it's not working all that well. My newly this summer purchased 90 gmc has become my daily driver work truck, and It's getting cold. Tonight will get down to 12 degrees, I would like to plug in truck and have the thing warm up quicker. I no longer live in Seattle, before you start wondering why I would like a coolant heater for the truck.

I also have an old tank heater on my 1970 gmc k2500 and it works very good. But that heater pulls in coolant off the bottom of the block, through the heater and into the top of the intake manifold warming the block very well.

The issue I have on my 90 gmc is the heater has 5/8 nipples and a 5/8 y fitting. So I have the heater drawing in coolant off the bottom of the engine block, through the heater into the y fitting and into the 5/8 heater core hose. Instead of the coolant going through the heater core and and into the top of the manifold, the heated coolant is going back through the y fitting and into the radiator, and only the radiator. I guess the radiator is higher than the heater core?

I see a few plugs on the top of the intake manifold, one behind the tbi and one in front. I'm wondering if one of the plugs is a coolant passage? The other option could be to buy some kind of 3/4 to 5/8 fittings and tap into the 3/4 heater hose that comes off the top of the manifold. I haven't seen any good options for those adapters and I would like to avoid having a bunch of clamps and adapters.

Any advice would be appreciated, thanks.