I have an 87 z28 with the 305, when i drive for at least like 20 minutes below 3000 rpm it majorly overheats. Its not the fan because i installed a manual switch for it on the dash. I also changed the thermostat and have even went without it in. Also all the AC componets were removed from in front of the radiator. I know the water flows throught the block. The water pump is new. But its becoming quite the problem, the starter doesnt have the juice to turn it back on when its turned off. And it's running way off the temperature gauge. I was thinking it was the timing or maybe a head gasket problem. I would greatly appreciate the input and any possible tests i could do. Cus im afraid the car will seize up if it doesnt start workin right. And if it helps it just started overheating like this recently after it sat for about a year after the front of the motor was taken apart to check to make sure the timing chain was all set and then it was simply put back together. It used to overheat but not to this extent. Anything could help, a repsonse is greatly appreciated.

I would look at condition of radiator and the timing. If the car sat for an extended period of time, the radiator may be partially clogged... Also, if teh timing is too retarded, it could lead to overheating ...

Check your Spoiler at the bottom of the radiator. Sometimes they get broken or fall off. It is there for a reason. It directs the airflow to the radiator as you are going down the road. Often the spoiler is missed and is a common cause for overheating.

Retarded timing and/or inoperative vacuum advance will also contribute big-time to overheating.

Check the spring inside the bottom radiator hose has not collasped.
When the engine is on the highway it stops the hose from sucking closed.
Also if the spring has collasped it may very well also have blocked the cooling system.

Bump!

Sound like the rad is blocked when it is hot check it carefully to see if part of the rad is cooler.
Flush that baby out!

Trick

If you have a blown head gasket you'll have water in your oil

If you have a blown head gasket you'll have water in your oil
Not always

If you have a blown head gasket you'll have water in your oil
On a SB chevy...usually not.
Thu u wiill have Co gases in the water system...this can be checked visually for bubbles or better still, a CO test at the local workshop for free to a couple bucks.

My girlfriend's '91 RS overheated twice. The first time was because it had the fan issue that a lot of thrid gen's have, so we had to have a sensor installed to tell the fan to come on at the right temp. The second time was because her upper radiator hose had a crack in it so the coolant spewed out and I put a new hose on it for her. I've read and heard from other Camaro enthusiasts that third gen's tend to over heat. Check the rad and hoses. After we flushed out the rad and installed the sensor and new hose, it hasn't overheated again.