Killergrl

ok, i've posted over in the cooling sections and baffeled everyone, including me on my over heating problem....got a 90 RS had a 305 TBI in her swapped out to a 350 tbi changed to the larger injectors the new engine has a mild cam in it. Ever since it's been running warm, it always runs about 220 around town and on up but never really goes in the red. just stops about 240 or so. weird thing is, is that it heats up more at higher rpms like on the interstate...around town its about normal on a cool day if its warm out then its about 220 in town.
I have gotten a new radiator for it, new thermostat, even tried taking out the thermostat, checked timing, checked for blown head gasket, new water pump, there is no blockage anywhere, air dam is there and fine, fan is fine and running right, not running lean, and since the radiator was brand new i thought POSSIBLY it could be a defect so we changed it out and put a 4 core one in so for sure it should run cool........but no. NOW my question IS....the ecm is the same one that was with the 305tbi, would that cause it maybe to not advance the timing enough at higher rpms (which is when is pretty much does the running hot)????????????????

RednGold86Z

iTrader: (1)

Is your base timing at the distributor set correctly? Is the EST bypass wire connected correctly?

vernw

iTrader: (2)

Might check that the fans are running the correct direction to pull air through the radiator.

midniteplowboyy

iTrader: (1)

How many water pumps have you tried on this engine? Is it correct for your belt rotation? Could be blockage in a head casting or intake gasket.

Killergrl

only have the stock single fan and yes its pulling air INTO the engine.....yes its the right water pump for the engine and belt set up. all the timing and such is all correct. for awhile there i thought i would need the dual fan setup with the upgrade BUT that shouldnt make it still run hot on the interstate it should get plenty of air out there.

RednGold86Z

iTrader: (1)

Collapsing the lower radiator hose?

RBob

iTrader: (1)

Is the TCC locking on the highway? What kind of RPM is the engine turning while highway cruising? What 350 is the engine, or where did it come from? Do you know what the head casting number is?

RBob.

twadam

iTrader: (1)

Just asking ... 'cuz the ECM being from the 305 should have a 350 PROM/.bin in it. Meaning the cylinder size and injector flow would both be larger. More fuel = cooler. Make sense ? Not sure this is your problem. Also are you using the 305 injectors or 350 injectors.

What kind of BLM's are you running ?

I made this mistake on a TBI once and got fed up and sold it. I had a 350 lower end and bolted the 305 top end on it. Stock 305 PROM, 350 injectors, 305 heads (inherently increased Compression) ... it was a mess. No wonder I never got it running correctly. If I remember correctly, I believe I was constantly getting a code 42 lean condition ? Now, knowing what I know (able to burn new PROMS) ... I would have a fighting chance.

Killergrl

its running about 2000rmp at about 70 mph
the 350's out of a truck we swapped all the sensors and top end over and put the larger 350 injectors on it. not real positive on the number will have to check.

I may be running lean actually, will check on that and let u know. other than the running warm problem she runs great!!

RBob

iTrader: (1)

OK, with 2K @ 70, I'd say the TCC is locking (if it wasn't a lot of heat would be added to the system).

The reason I ask about the engine it that different heads require different SA timing. If the SA timing is too low that will dump heat into the engine.

Try this, advance the timing at the distributor by 4 degrees. If now set at 0 BTDC, change it to 4 deg BTDC. See if that helps. If so then they are heads with a camber design that requires additional cruise timing.

You mentioned that the belt set up is correct for the engine. Measure the diameter (or circumference) of the crank pully and the water pump pully. If the crank pully is smaller then the water pump pully it will run warm. I've run into this before. Some GM setups under drive the water pump, I don't know why they did it, but they did. 'Upgrading' to a different setup where the water pump is overdriven took care of the engine temperature issue. Like yours, it had always ran hot on the highway.

To check if lean, put a scan tool on it during a highway cruise. If the BLM tops out high along with the INT being greater then 150, then it very well could be lean.

RBob.