[BigJeepAZ]

Im not really sure if you guys can help me, but i havent found nyone else online, and im sure u guys know custom setups pretty well.

My problem is that my jeep will overheat like crazy here in arizona. It does not matter if it is idling or runnin at 35, 45 or faster, it will always overheat. It takes it about 15 min maximum, and then it will be 260+ degrees and boiling over everywhere. I think it might be an issue with my timming (hence this is an engine swap, and im possitive it isnt timmed right).

Here are my specs.

I have a 89 4.3l Chevy V6 (262) - NOT Fuel Injected
The induction is through a edlebrock 1401 carberater (i think thats 650cfm).
I have replaced the original jeep radiator for a 2 core aluminum griffin (22"x19")
No thermostat
th350 trans
there is an electric fan, its a 16". I run it all the time, and i think its about 900cfm.
the mechanical fan is small, a flexolite, maybe a 16".

Im not really sure about what to do next. I cant fin the factory timming specs anywhere, since the engine used to be efi, so i have been adjusting it back and forth trying to find a generaly good point. otherwise, i have checked everywhere for vacuum leaks and found nothing.

i know it shouldnt overheat, because last year i drove it all summer with no problems.

Thanks in advance guys

[Shortblock]

BigJeep,

Put a thermostat back in the motor. Try a 160 degree thermostat. Running without one can let the water flow through the radiator so fast that it can't give up any heat. Also, if you are running the distributor from an EFI engine, it doesn't have any sort of timing curve. You just have the timing that you set at the damper. You will need to get an earlier model distributor that has a mechanical and a vacuum advance built in.

[Shortblock]

After turning my brain on I see that you said the 4.3 wasn't EFI. The problem may be that the timing is run by the Computer, so you will still need an older style distributor.

[engineguy]

I think Shortblock is right on with the thermostat diagnosis. Without the 'stat the coolant does not spend enough time in the radiator to transfer heat to the outside air. The distributor should be a non-computer controlled application with vacuum/centrigugal advance. Heed this advice, as well as having a good fan and shroud, the Jeep should run cool.

[blndweasel]

Did you make sure your water pump is flowing? Yeah you definitely want a thermostat in there. Do you have a fan shroud installed on the mechanical fan? Without a shroud, and with that 900cfm electric fan, it seems to me like you don't have enough airflow across the rad - which since its aluminum and doesn't transfer heat as efficiently as copper or brass, and since its only a 2-core, along with the fact you're not running a thermostat... this might be the issue.

What are you running for coolant? Make sure you're running Antifreeze to raise the BP, and try throwing in a quick dash of dishwashing soap to lower the surface tension, or buy some of that Redline Water Wetter or equivalent royal purple or such coolant additive. I usually only add about half a bottle of that stuff, cause a little goes a long ways, and it seems to decrease the effectiveness of the antifreeze for raising the boiling point.

Just some ideas. Let us know what you find out.

The Blonde Weasel
San Diego, CA

[gumby]

totally different train of thought. But, late model 4.3 chevy engines run a reverse flow water pump. could you have the wrong water pump?

[BigJeepAZ]

to answer the questions on the distributer, i am running an older HEI destributo with vacuum advance. so there is no computer controlled distribuor left. Im sure i have the water pump runing the the right dirrection. The only thought that i have is the mechanical fan. Since everythin is packed so tight, i bought a regular rotation fan (this engine runs a serpentine belt system, and the fan rotation should be reversed). I did this because the width of the fan was pretty small, but i had to remove the rivits and flip all of the blades to get the air to flow in the right direction.

do any of you guys know where i might get a small (diameter and width) mechanical fan to put in there?

Im going to try and put the thermostat back in right now... thanks alot guys.

[CJ2AWILLY]

Bigjeep, I have a 48 '2A with a Chevy 350 and had the same problem. I returned the thermostat (160) and because I only have 1/2" between my radiator and waterpump I run an electric fan on the front of my radiator. Before the 350 I had a Buick V-6 and used a fan from a B18 Volvo due to it's small size. The hottest the old '2A has gotten with the elec fan is 210. The advantage with the elec fan is that with an additional switch I can control when I want the fan to turn on when I'm out 4 wheeling. If you want to stay with a mechanical fan, just take some measurements and head for the wrecking yard.

Good luck...

[BigJeepAZ]

i just finished putting the thermostat back in and taking it for a test drive. I was going to drive it to the gas station and back, but it heated up way to fast. I wasent running the ac or anything, and i wasent driving up hill either. Does anyone have a 4.3l that can give me the correct timming specs? I have it set to 4 degrees BTDC right now, an i had it at 8 just last week, neither of these worked out to well. I might try to pick up a 160 thermo on the way home tonight, but i have to go to work right now.

[trees]

Did I understand this correctly: you have a serpentine belt on a GM motor which means you must have a reversed fan, so you took a regular fan, removed the rivets and turned the blades over??? Dont think this will work correctly. I did some pretty hard figuring when I could not find the correct diameter reversed fan and considered doing the same as you, but for some reason, I thought the curve in the blade was not correct. Also, re-riviting a flan blade is semi risky. Hope you used new, tight fitting rivets and got them seated very good. A wayward fanblade is a Tasmainian Devil under the old hood, not to include the havoc the out of balance fan can do before you can get it shut down. Not good in the Arizona Deserts. Even though it is cramped in the Jeep engine bay, there was most likely a fan in there before and the correct reversed fan should work.

Trees

[MHenricks]

I'm really familiar with the 4.3 but I thought I'd throw this at you. Is it possible with the engine swap that maybe the water pump was designed to run the opposite direction. This has happened before when swapping 350 is early model versus late model. Early models using regular belts run one direction while late models with a serpentine belt run in the opposite direction.

You may have already checked this, just a thought.

Good luck

[engineczar]

Is it possible that with the engine swap that the thermostat housing and/or the top of the engine is now higher than the radiator cap and that there's a lot of trapped air in the motor?

[willys36@aol.com]

Have you had the radiator cap off ahd watched the water? With the engine warm and the thermostat open, you should see a lot of turbulence indicating good water flow.

I don't like the sound of your dual fan setup. A 950cfm fan is fairly small and the combo you have may be restricting air flow. It has been my experience that poor air flow is the cause of the majority of overheating problems in modified cars. Is there room in your engine compartement for the hot air to escape?

In summary, you have extensively modified both water and air flow circuits and one or both are performing inadequately. You just need to do your detective work.

Also, this topic has been covered in great detail in the past on this board. Do a search for more info.