Sorry, I noticed over 200 threads about this topic and my answer is probably in there but hear I go. 1994 LT1 (5.7) transplanted into '84 elcamino.
Q. Does someone have a legible diagram on how the heater hoses are hooked up for a 94 caprice? This is where I may have the problem. I believe I need to stay with this 94 caprice routing system.(unless there is another routing way to go)
Reason: my 94 Caprice "B" carline Service manual doesn't show the routing clearly.
This is what I do know:
1)Temp. rises up to 260,operating temp is 215-220
2) temp check via electric gauge (OEM 84 elky) and Equus mechanical..reads the same.
3) new 10 yr old thermostat changed out for a new thermostat (with orifice) and system bled via screw on waterneck and with heater on.....inside cabin heat seemed to be of room temp. I may indeed not have completely bled the system...IDK though.
4) as your facing the waterpump, lower left heater hose outlet goes to OEM, 2 port elky heater valve , then goes into heater core, then out of the heater core to upper left heater hose outlet on pump...this is where I think the mistake is, I need a 3 port heater valve but the 3rd port goes to?? does it by-pass the heater core and go back into the upper hose outlet via a T in the line? Note: after 2 yrs of being installed the metal port(on the OEM elky heater valve) end had partially rusted while installed inline and a small amount of debris was still there, seemed it never circulated through the system, which leads me to think coolant wasn't flowing.
5)my radiator is the original replacement for the caprice (new), which has upper radiator outlet and lower rad. outlet (only 2 ports)
Elky is still a garage Queen, 100% restoration in process, has been ongoing for 2 1/2 yrs, finishing up the interior now (that's whats left), I have had it sitting idling for up to 15 minutes at a time with dual electric 3000CFM fans (both on), backed it out of the garage to the end of the cul-de-sac and back (about 200 ft once). Hope all of this is enough info to get started. thanks!!