Overheating 350

[starkey]

Like the title says.. She's overheating.

Got this truck on trade for next to nothing, and here's what it had:

74 Chevy with 92 carbed tbi 350
Edelbrock 600, stock GM 4 barrel manifold, HEI dist.
Original v-belt system.
Direct driven Flex Fan, correct rotation.

What it was doing when I got it fired up:
Getting hot (240, verified with temp gun) at idle within 2-3 minutes.

What I did to try and remedy the situation:
Flushed radiator, replaced water pump (correct rotation w/ v-belt)
No thermostat
heater core bypassed
new plugs and wires, radiator hoses
Set timing at 8 deg at 750 rpm with vac advanced unhooked and plugged.
Pressure tested headgaskets, no bubbles.

It's better, but still getting hot within 5 mins of idling. I can spray the radiator
and the temp will come down.
Now, I have not verified that the intake manifold gaskets are correct.
I need advice on what gaskets to use for the TBI to Carb swap.

Thanks,

Stark

[Captkaos]

Does it have the TBI or carb?  Reason I ask is because of your last question..
Does it have a fan shroud?  Clutch fan?
What temp is it running now? 
I would recommend putting a thermostat in it.  180 degree.

[starkey]

It's got the edlebrock 600 carb on it.
Original fan shroud in good condition,missing no bolts.
Direct-drive Flex Fan - no fan clutch


I had a 160 thermostat in it, heated up way faster than without a thermostat.

After 5 minutes of idling, it'll be sitting at 240. Spray the radiator down and it'll come down to 210ish. Doesn't matter if i kick the rpm's up or not, it's going to climb to 240.

[Captkaos]

Is the water moving in the radiator?

[starkey]

Yes.

The reason I asked about the TBI to Carb swap is to gain insight on what gaskets are used to mate the old style GM 4 barrel manifold to the swirl port center bolt heads.

Stark.

[Fairlane514]

I would also use a thermostat, 180........you may have some air trapped in the cooling system.  I would also get rid of the flex fan and go with a fan clutch and OEM fan.

How many rows does your radiator have?  How old is the radiator?   I know you said you flushed the radiator, but it may be blocked significantly enough to cause your problem.

[zieg85]

By chance is the waterpump going the right way?  I believe '92 serpentine belt set up ran the waterpump in reverse so the fan blades were also pitched opposite.

[starkey]

Yes, the water pump and fan are turning clockwise, just like the engine (looking from front to rear)
I went to the parts store and bought a brand new water pump for a 74 chevrolet with a 350. It is the correct water pump, as stated in my first post.
The fan is pulling air through the front of the radiator.
The fan shroud is in place and not compromised.

I'll probably mount an external electric fan in a pusher config, along with the current fan setup, and see what happens.

I don't know how hold the radiator is, but it is OEM.

I'm thinking the yayhoo who put the intake on used the incorrect intake gaskets. There is just not alot of water moving through the top hose. Next time I work on it, the cast iron manifold is coming off. 

[Fairlane514]

It seems to me, if you have a restriction in the flow of water, spraying cool water on the radiator while its running would have no effect, but you say it does.

You really shouldn't need extra electric fans to make the system work properly, especially on a stock motor.  If its an OEM radiator, I would remove it  and take it to a radiator shop and let them evaluate it.

I have a 1984 C10 with a Goodwrench 350.  I have a new standard flow water pump, new fan clutch with original fan, new 3 row aluminum radiator and original shroud and 180 thermostat. It runs 180-185 with A/C on, here in Houston.

[starkey]

Thanks for the insight Fairlane. Won't be able to work on the truck till the second weekend in July, i'll jerk that rad out and see if I can't get another one.

And yeah, if you spray the radiator with a hose, the temps come down.

With your comments, i'm leaning towards the flex fan being the main culprit.

I haven't had a chance to run it down the road yet, the master cylinder was out, no brakes. Put the new one on, just didn't want to crawl underneath the truck in a patch of stickers to bleed the front brakes.  I'm betting it would cool down once there was a large amount of air rolling through the front end.

[starkey]

Ok fellas, here's the skinny.

Got to work on the 74 this weekend. Bled the brakes and took it down the road. Within a quarter mile, temp was on  the verge of pegging. This is: without a thermostat, new water pump, correct fan with new fan clutch.

When I got to back to the house, I noticed that the top radiator hose had no pressure at all, but the heater hose was pushing water back into the radiator, as designed. Keep in mind, this is WITHOUT a thermostat.

I took the radiator out and ran water through the top radiator hose, and water exited the bottom hose, and visa-versa. I did not take the water pump off, although hindsight says I should have.

I installed a new Stant 180 degree thermostat, filled the block with water, installed radiator and filled through the top radiator hose, then topped off the radiator when fully assembled. Started the engine, and after about 2 minutes of idling, temp was pegged, IR gun said the head was at 240. Sprayed the radiator down and it cooled to 210, but the only side of the radiator getting hot is the lower hose side. The top radiator hose is not getting any fluid, meaning there is no flow through the engine except through the heater hose, which is visibly moving water.

I have only two other possible solutions that I've come up with, and I'd like to hear some more from you all. I should add that the radiator cap has a nick in the rubber gasket, which may cause a pressure problem, but I would not think that it would cause the severe overheating issue.

1. the intake gasket is installed incorrectly, causing a severe restriction in the top water passages

2. the block is clogged near the water pump.

Good news is that I found the RPO codes under the half-inch thick dust on the drivers fender well, and this bad boy has factory 4.56 gears! And, while road testing, the speedo even works! 

[Stewart G Griffin]

can you post a picture.  Specifically of the fan+fan shroud?

[Captkaos]

Did you make sure you filled it completely?  Just filling it up with it cold won't allow it to fill completely  If water isn't going through the top of the radiator you either haven't filled it enough and or have an air pocket or your thermostat is stuck.  Did you test the old one in boiling water, did you install it correctly?  Is the overflow working properly, is it filled up to pull coolant in when the pressure changes?

Open the cap and start the truck and see if water is moving through the radiator when cold and let it get up to operating temp (190 degrees) and see if is still moving.

[starkey]

Capt, yes, the system is as full as I can get it. Nose up on jackstands, radiator cap open, the works.

Yes the tstat was checked in a pot of water and it opened. No i didn't use a candy thermometer because I don't make candy. It is installed correctly, I am no dummy.

Overflow is hooked up and filled about halfway. Is it working? who knows. Impossible to tell when the radiator cap is off while filling.

Water is sucked up through the pump and put back in by the heater hose from cold until molten lava.

As i stated in the first part of my last post, there is no water coming through the top hose, regardless of thermostat or no thermostat.

"Got to work on the 74 this weekend. Bled the brakes and took it down the road. Within a quarter mile, temp was on  the verge of pegging. This is: without a thermostat, new water pump, correct fan with new fan clutch.

When I got to back to the house, I noticed that the top radiator hose had no pressure at all, but the heater hose was pushing water back into the radiator, as designed. Keep in mind, this is WITHOUT a thermostat.

The top radiator hose is not getting any fluid, meaning there is no flow through the engine except through the heater hose, which is visibly moving water."



Stewie, I assure you that the fan and shroud look just like you'd expect on a 74 chevy, because I found a 78 at the junkyard and pulled the fan and clutch off. The clutch was shot, so I got a replacement heavy duty thermal clutch from Advanced. I'd take a picture, but the truck is at my land, which is 150 miles north of me.

[bd]

You may be on the right track with the intake gaskets being the wrong ones.  If TBI intake gaskets were used, they may be reversed end-for-end.  The TBI intake gaskets have a restriction in the heater hose port at the back of the intake.  If switched end-for-end, the restrictions will inhibit coolant flow through the engine and radiator.

Edit:
a) Using your heat gun, do both heads measure the same temp when overheating?
b) Can you post a pic of your heater hose configuration/routing?
c) Before removing the intake, use an old speedo cable to probe the coolant crossover at the front of the intake to determine if the coolant ports are blocked by the gaskets.