OK, so I searched, and found the replies to be for the exact opposite of my problem. I heat up when on the highway. 50mph and below, I never get over 205-210. On the trail, she's at 200. On the highway at 65, she'll run close to 230 with the heater on full blast!

It's a SBC 305, JT outfitters 4-core, and a big (i think 16") electric puller fan. Stock 195 t-stat & water pump.

I think the air can't escape fast enough from the engine compartment at speed, and is creating backpressure, not allowing air to flow thru the rad? I've tried turning the fan off at speed, and it makes it worse.

I dont' see how a lower t-stat would help, since mine is fully open, and trying tis best..a 180 would only make it open sooner, but would still get just as hot, no??

The timing WAS off when I bought it, as I could see the headers glowing on the highway thru the holes in the floorboard. (Shorty blockhuggers). I've now set the timing, and it helped a little.

So, what to do, preferrably cheap? Water wetter is going in tonight. I can't take the fenders completely out yet.. maybe trimming a bunch off the inner fender would help?

I had the exact same problem.

Your fan is inhibiting the air flow at speed. One way to get around this is to cut some holes in the shroud with rubber flaps that will flip open with the pressure is high enough. You will have to play around with it until it works right. If you check out cars like VW's that came with a electric fan they will have just what I am describing. it's like a door that pops open and lets the air flow through at speed.

You can also get this kind of problem with a hose that collapses under high RPM. The cavitation and flow of the pump can cause the hose to collapse. That is why some hoses need a spring inside of them...

Try taking the fan out and test-driving it at speed. On the highway, you should not need a fan at all.

I have also seen trucks do this that had a hairline crack ABOVE the water line on the top tank of the radiator. Just enough for some pressure to get out and cause the engine to overheat.


-Stumbaugh

Thanks for the info....

I know it's not the rad... I just put it in Saturday... new.

There's really not much of a shroud around the fan, but I'll try what you mentioned, cutting holes... I've seen what you talekd about with the flaps...always wondered why they did that! :D

I will also check the bottom hose to make sure it's got a spring in it...

Good advice! Thanks!

I had a similar overheating at higher speed problem. Turned out that the distributor was bad. I swapped in a "new" one from a junkyard and haven't had the same problem since.

I had a shop (dare I say it aloud) look at it with the proper tools to determine if it actually was the distributor and they confirmed my suspicions.

I am voting for the collapsing hose. Mine did this. The guy I bought it from install the bottom hose with out the spring and mine was overheating at high RPM, same thing basically. So if I dropped it in low, grand 1 st, and hit 2500 for any lenght of time it would start to heat up.

I have been fighting heat as long as I have had my Cruiser. One other thing to look for is a bad vacume assist for the brakes. any vacume leak will lean out you air/fuel ratio and then you run hot! also you can add an oil cooler they help quite a bit.

try removeing head light bezel.

Originally posted by Cruzilla
One other thing to look for is a bad vacume assist for the brakes... also you can add an oil cooler they help quite a bit.

I would check that, but my cruzah doesn't HAVE power brakes... Gm master cylinder, no power assist.. It's a good workout.

I looked closely at the fan last night, and there's not enough plastic around the fan to cut even a 1" hole in it...

Me being the big dummy, I totally forgot to see if there is a spring in the lower hose...:zzz:

Adding an oil cooler isn't a bad idea at all regardless...

If you are running a winch in front, and it's mounted above the frame rails, it is likely redirecting airflow at higher speeds to OVER your hood and not into the radiator. This is common on offroad trucks with high-speed overheat problems. One solution is to move the winch to between the frame rails with the fairlead thru the front bumper.

I've also heard that adding hood louvers can help, but they aren't cheap to have created...

Yup Brian, I sure am, it's an OLD Ramsey 9k that needs a re-build, so I might as well take it off.... and yeah, it's on top of the frame rails...

Also, my hood has louvers on it... I was wondering how much it could run to have more made, but I'll try the cheapie mods first.

Do you have any kind of valve inline with the heater? You should use a valve of some sort to slow coolant flow through the heater core. Often the heater core loop offers a lower flow restriction than the actual radiator and as you can imagine the air flow through that is substanially less. So, two things to do:
Install heater valve, and or put a restricted heater hose nipple in the intake manifold.(it looks just like a normal heater hose nipple, but with a smaller opening, restricting flow through the heater core )

An older mustang I have dealt with had a similar problem and a valve and restricted heater hose nipple helped out alot(15 deg)...

Depending on where you live you can cut down on the antifreeze % to about 25%. I set my 305 up with a 25% mixture and two bottles of the water wetter and it hovers around the thermostat opening temp(195) ALL the time.

your winch cant be up higher than mine...hehe. im still runnin the 2f though....so its impossible to overheat that bad boy. ask dogwalker....from cali to colorado in his fj60 w/ a hose leak...no water and never skiped a beat....lol!:eek: :flipoff2: :rasta:
http://www.rivercityrockcrawlers.com/~dcruiser138/images/8274rght.jpg

what happened after you removed the head light bezel??

Well, got out the grinder, and cut the rear 1/2 of the inner fender off...felt good to cut metal!

the lower hose does have a spring in it, so that's not the problem (I wished so bad it was)

I added 2 bottles of Water wetter, and got quite a bit of air out of the system by shutting off the fan and letting it get to 220-225 while holding the catch can over my head, making it the highest point...

Since the POS Ramsey winch that was on the truck is dead anyway, I removed it..

Between all that, I damn well better have solved the cooling mystery!

I really do wanna keep the bezel...without it, I'd get even more "nice J**p" comments! Plus, I like the chevy bowtie cutout that's on the grill mesh. :rolleyes:

I'll report how it works, and thanks again for all the help...

Off-topic, I'm never gonna get alot of posts on here... The search works so damn well that I hardly ever have to post! How's THAT for a "good newbie"? :flipoff2:

well you can get more posts buy helpping others.

I sugested removeing the bevel to see if it helps,

it did on mine but I also like the looks whith it on so compromized and cut the center sections off
then welded up whare I had cut them off.
Not many peopple notice the diference and when they do they say good idea,