I recently just got my 81 z28 back after have a friend do a few odds and ends and some much need tweaking to the motor. After picking it up last night I have a cooling issues, again! The whole way home bout 45mins the temp gauge just kept slowly creeping up. It would hold a steady temp on the highway but any time I had to stop it would slowly creep up. By the time I pulled in the driveway the gauge was right at 220*. Last fall I had a brand new 3 core aluminum radiator installed with a new 18in fan I thought this would fix my issues, but guess not. Another friend looked at the car and said he thinks it's the fan, suggested a possible 19in fan with better fins to pull more air at stop or slowed speeds. Any thoughts??? The motor is a 355ci with all aluminum heads and manifold (Edelbrock top end kit rated at 410hp). Motor is finally running good and strong and most importantely reliably but now I have the overheating issue, please help!!!

Thanks,
Bryan

 

What kind of "odds and ends" did your friend do, and were there more odds or more ends?
Did he "fix" the ignition timing? Perhaps it's too far retarded, which can make an engine run hot, sometimes more so than what being too far advanced can do.
Also, do you have a fan shroud on the radiator? Not having one won't let the fan pull air through the radiator nearly as well.

 

The guy thaT did all the tweaking on the motor knows his stuff. He had to fix all the issues the engine builder didn't take care of (long story). The motor is finally running like it should, it's just running hot. The car does have the original shroud on it. There is no timing issues with the car I believe. Is a 19in fan a better fit in the stock shroud? Any recomendations on a fan that will pull more air?

 

I'm going to go out on a limb here and assume you have the sending unit for the gauge in the most popular place, the head? If so, move it to the intake manifold. Aluminum heads dissipate (move) heat better and faster than iron heads do. This can also mean that you are likely getting a false reading on what your true water temperature is inside the block, that's what really counts. If you want to verify coolant temperatures for your own peace of mind, pick up an infrared thermometer and take some readings, like for instance, at the water neck. And if you want to be really trick, run two gauges...one for the engine coolant temp (intake manifold) and one to read the head temp.

 

You are right, the sending unit is right on the left head. So if I move the sending unit to the intake manifold I'll get a better (true) reading? My only question then is, I've always been told the with aluminum you don't want to go past 210*. With my sending unit in the head now its saying that it's that's hot, is that not really an issues? Thanks for all the help.

 

Even 220, where you say your engine is getting, isn't considered "overheating". Heck, talk to the aluminum head LT1 guys (I have one too, btw), where it's considered "normal" for the engine to get past 220. In addition to internal engine heat, your aluminum heads are also soaking in heat from the exhaust manifolds/headers. Once you move the sending unit, I think you'll be surprised to find out your engine isn't really "overheating".

 

I was looking at the Camaro when I got home and realized my friend had already moved the sending unit to the manifold. So the high temp reading I'm getting is coming from the manifold. Also, I looked at the fan. The fan that's on the car is only a 4 blade with not much pitch to the fins. Any suggestions on a fan that would work and pulls a lot of air at slow speeds? Thanks again.

 

Any recommendations guys???

 

sounds like you have a pretty ancient fan on there if it's 4 blades you could pick up an aluminum flex fan for it that may help. if your still running hot you could always go the electric fan route.
it doesn't sound like it's really running all that hot though.
Dave