Issues with running HOT on freeway after switching to aluminum heads

[painterdude923]

My 1997 2wd ranger with a carbureted 302 ran at the right temp always when I had the cast iron 351 Windsor heads, then I switched over to a set of flotek heads,intake and cam upgrade, now runs TOO hot at freeway speeds but just fine around town and at lower rpm. I've been running a 4.0 radiator the whole time. Don't know what's going on now?? Any thoughts??

 

[19Walt93]

More compression and more cam usually mean more heat. What are you running for a cooling fan? A more aggressive belt drive or electric fan might help but a bigger/better radiator is probably in your future. How hot is "too hot"? Do you still have the stock gauge or one with numbers on it?

 

[Sharky]

a hose may be collapsing at hi way speeds or a partial block in the radiator will do that.

 

[painterdude923]

I'm running a Taurus sho fan with a 180degree high flow thermostat, autometer sport comp gouges. It runs about 180-190 around town and 210+ on freeway speeds! So I get off the freeway and take the back roads.

 

[19Walt93]

If the problem is at highway speeds it's not the fan, it's the radiator. Either the rad is too small or airflow is restricted, at speed you shouldn't even need a fan. The fan shroud isn't restricting flow is it?

 

[painterdude923]

Didn't have any cooling issues before the head,cam and intake swap. Same radiator and Taurus SHO fan. Made sure the radiator was flowing by running hose at full through both ends. Guessing since now I'm running a little higher compression, the 4.0 radiator can't keep it cool enough. Even bought a nice aluminum radiator for a v8 explorer, just wouldn't fit between the frame rails at the bottom. So I sent it back. Waiting on refund.

 

[tinman_72]

210 really isn't that hot, but it is unusual that it runs cooler in town.

 

[RonD]

I would agree that 210deg is not a big concern, you would do that driving up a longer grade or pulling a load

But you shouldn't see that just driving at highway speeds
Its possible you don't have enough cooling capacity in the radiator, you can test that by turning on the heat in the cab and running blower at HIGH, adds extra cooling capacity to the system
If you see temp drop down and stay down then larger rad may be needed with those heads

You can use a temp gun on upper and then lower rad hose, should see a 15deg drop, 20deg with fan on, at highway speeds it would/should be close to 25deg drop

Its possible the thermostat is not opening fully, which was not an issue with cast iron heads
Thermostats are not all that complicated, just wax that melts at certain temps so while reliable they are subject to odd failure modes
If you wanted to test that you could gut an old thermostat and install that, you need the restriction of the thermostat plate
Then see if temp stays down at highway speeds, if so the radiator can do its job

Are you running an under drive pulley?

 

[Junglejoe]

Trapped air, clasping hose, bad thermostat, dirty radiator or to small radiator

 

[RonD]

You had to use MLS head gaskets with aluminum heads, or should have, lol

Did you compare it to the old head gaskets as far as the coolant passage holes?
Long shot, but not a no shot

 

[painterdude923]

No underdrive pulley. Normal explorer fead. Cut off the threaded portion off the water pump pulley and running a Taurus fan. Tried running it without the thermostat to take that out of the equation. Still the same so I put in a high flow 180degree thermostat. Going to get a different radiator next month when I have the money. Not sure which one yet.....

 

[Shran]

What's the ambient temp outside when this is happening?

Mine will usually run around 180-190 on typical summer days when the temp is under 90 or so. If it's hotter out, I see engine temps of 210 or higher if I'm really working it off road as well as on the highway but at 70mph I am guessing I'm running over 3000rpm. We had one day this fall where it was almost 100 degrees out and it crept up to 230 on my way back to camp.

FWIW I have the old Duff V8 swap radiator (now made by Northern I think) plus a high flow water pump, 180 degree thermost, two electric fans in a pusher/puller arrangement on a stock 80's 302.

Just a thought but on mine the upper radiator hose is slightly higher than the radiator cap. I have to fill the radiator and then put a lot in the overflow reservoir and let it suck from there and fill itself, otherwise I get an air bubble in the upper radiator hose and weird engine temps. Maybe an issue on yours?

 

[painterdude923]

In central Florida, been upper 80s lower 90s. Even when I'm only going about 70mph.... like anything over 1600 rpm it starts getting hotter! I haven't drove too far cause of it! Before when I was running cast iron heads i drove back to Michigan and Florida a few times! Never had a cooling issue. Feel like I should have left well enough alone ya know?? Lol

 

[19Walt93]

Are you sure the head gaskets are oriented properly? Most are marked with "front" and it will look like one is upside down. My favorite 302 head gaskets are Felpro 9333-PT1's and they have tabs that stick out a little at the front lower corner of each head. Running the heater on high as suggested is a good way to test if the radiator is adequate.

 

[painterdude923]

I had those gaskets for the 351 heads, I loved those! I have had the heads off and replaced the gaskets and paid close attention to that! Been a headache for me that's for sure! Still drive it just not distances and just not comfortable with it running above 210 ya know? I have thought about cleaning up the cast iron dooe 351 heads and putting them back on and keep trucking!