old truck guy

I just finished installing my new 355 and drove it a few times and its running hot, sitting still and going down the road. The build is as follows - fresh L05 shortblock, vortec heads, crusader marine vortec/tbi intake (identical to gmpp's w/o the egr provisions), 46mm tbi, headers and comp 252XFI HR13 cam.

I used a new extra capacity radiator, new ac delco 195 deg thermostat, new hoses and a new vortec style water pump and installed the external bypass to the front of the intake. Thermostat opens right at 195. Still working on tune but have been nothing but rich so far. Tuner pro is showing engine temps between 210 and 225 while driving 200-205 sitting at idle. Confirmed temps with a heat gun and a snap on scan tool. Unplug the sensor and it goes to -40 and it displays accurate ambient temp before start up so I'm pretty confident sensor and wiring are good. Truck temp gauge only reading 180-190 off the head and heat gun shows 10-15 deg cooler at back of intake (at heater hose connection). Highest heat right at t-stat.

After more research the last couple of days, I think problem lays between the intake and the bypass. Read a GM bulletin on tbi intakes and cooling today and it said the back coolant passage restrictor plates found on tbi intake gaskets are essential and that the coolant flow should go from the front of the intake to the rear, out the heater hose and back to the water pump. No restrictor and flow is reversed thru the intake causing uneven heating. Suspected problem #2, bypass never closes not allowing enough coolant to go thru radiator.

These are just my thoughts. Looking for knowledge and what has and has not worked for others before I go making changes.

Thx

Ozz1967

iTrader: (4)

Factory electric fan set up?

If so, factory fan turns on at 225, if dual fan, second fan turns on at 238.

Just a thought as the cars were designed to run hotter for emissions purposes. So even with a 195 thermostat, the car will run in the 220 range by the factory fans.

Also,and you may have already done this, but you did burp the cooling system after putting it all together right?

novaderrik

retarded timing will cause an engine to run hot... are all the air deflectors and what not in place to direct air thru the radiator?

but honestly, your engine isn't running too hot. you might be giving up a couple of HP on the top end, but if it isn't boiling over it really isn't overheating so as long as it doesn't ping and rattle when you go WFO i wouldn't worry about it.