I'm back with another question in hopes of maintaining my 88 IROC.
I have been having problems with my car seeming to overheat while I'm driving down the highway, then when I come to a stop and idle for a couple minutes it cools down.
I had a coolant leak, replaced the waterpump last night and I don't have a leak anymore. It has a stock 1974 2 bolt main 350 with an intake, 650 cfm edelbrock, stock manifolds and a v-belt driven clutch fan.
The radiator is stock for the 1988, with a 1982 shroud over the top of the fan. The radiator is in decent condition, and seemed pretty new when I got the car 1 year ago. I do not have the lower shroud under the bumper to direct air into the rad, but I also do not have the lower shroud on the mechanical fan.
I am currently hard on cash but need to fix this problem to do my commute to work daily. My question is, where do I start?! Should I but electric fans, a new rad, the lower bumper shroud or the lower fan shroud!? I can't do them all but I know I will eventually need them all. What does everybody suggest?

 

 

Need that air damn to run highway speeds,I made a temporary one out of a strip of conveyor belt 9 years ago,lol,it's still there.

 

Gotta have the air dam. PERIOD. Start there.

Its job is to create high pressure in front of itself (the radiator intake), helping to push air though the rad; and to create low pressure behind itself (the back side of the rad), thereby sucking air through the rad at the same time. It VASTLY improves the efficiency of air flow over the rad; maybe even doubles it.

I like nhgator's suggestion. Similar to my own. My own personal one is, a strip cut off of a 18-wheeler mud flap. Bolt it across underneath the rad with a piece of Home Depot angle aluminum, make it of such a width that it comes within acoupla inches of the ground. Hard enough to hold its shape, soft enough to withstand parking curb strikes.

Next thing would be, replace the fan clutch. Get a GOOD QUALITY one. The "thermostatic" type (stock), NOT "centrifugal".

No you will NOT "need them all".

 

100% what everyone said about the lower air dam. I had an 88 IROC-Z convertible that was doing the exact same thing. Previous owner even installed an aluminum radiator with zero improvement. I bought the car, saw it didn't have the lower air dam, installed an NOS one that I bought for $65, and the problem was solved. These cars absolutely HAVE to have the lower air dam

 

UPDATE:
I have installed a custom lower air dam with galvanized metal, 31" wide and perfectly covers and seals the entire bottom of the rad.
This has definitely HELPED but not solved the problem. I can now drive longer and don't get as hot, but the temperature still slowly creeps up while I'm cruising at highway speeds and cools down at idle and around town.
The next suggestion I read was a new clutch on my fan, I do not believe the clutch is bad but I am sure a new one won't hurt either. I was just wondering if anybody else had this problem. Was thinking maybe run a coolant flush through it, don't seem to be burning or leaking any.

 

Is your transmission torque converter clutch locking up in 4th gear or is it slipping. If not locked up that can put alot of heat into the radiator.

 

Since you mentioned you are low on cash, I'd hold off on the coolant flush, and just run the car with radiator cap open (at idle, in the driveway), and make sure it is exchanging water periodically once the car warms up. you should see a nice healthy flow of water when the thermostat opens and subsequently closes (stops) once the new cool water is brought into the engine. from what I understand, this will also help get any air pockets out that could be in there.

 

This very well could be a problem. In 4th gear my rpm can still fluctuate up around 1000rpm before making an impact on the trans.
any suggestion for diagnosing and fixing this issue? The trans was rebuilt a year ago and I put a new 1500 stall lock-up torque converter in it

 

Pics? to ensure you re talking about the air dam that is missing...


Put on an air dam if you are...... nothing you do will halp unless you are getting good air low to the radiator....


you can fabricate one or go find something from another car etc... you can use in the junkyard for now since you are low on funds...