I took my truck on it's first trail ride. Hit 220F with a 180F thermostat / 190F fan switch. I have an aluminum Howe radiator, aluminum heads, medium-hot 302, 2000cfm 18" puller fan. Everything is new. Low range, 2nd gear, 3000 rpm for 20 minutes at 6000ft. and 80F

I don't have room for a mechanical fan..... should I add a pusher fan?

You sure it's bled well? Seems your setup should be plenty good... How many cores on the radiator?

J.D.

That sure seems hot, I was having issues like this with my 460 with a 4 core rad. and a pusher 16" electric fan 180* T stat. Found that I bumped my distributor with my arm the last time I was messing around and when I re set my timing it ran cooler.

ditto on burping the radiator and checking the timing

I assume there is a fan shroud ?

IMHO nothing beats a working clutch fan set up which can be achieved if you convert to an Explorer serpentine set up

Same question as Rox. Are you running a shroud? Those make a huge difference.

I'm running a very thin puller electric fan that has a small shroud built in. I recently filled the entire cooling system.... slowly while the engine ran and bled it at the top, back of the intake and the upper hose.

I have a small exhaust leak at the header flange AFTER getting the motor hot, too.

Can you tell by the gage that the t-stat is opening?

Might see if you can park it nose high and try to burp more air. Sometimes it's a real bear to get it all out.

J.D.

Around town, I can "see" the thermostat opening / closing around 180F. But, I have had trouble triggering the fan switch sending unit (top / rear of the intake).... probably because of air pockets. It wasn't an issue when I overheated......the fan was howling the whole time.

I think I'll make some bleeders for 3/8 NPT fittings and put in one or two in the top of the intake.

How big is this puller fan? You want one that.will cover more of the radiator. Also a lot of cfm. If you can find the dual taurus fans to put on. Each is dual speed too. I've had great luck with my clutch fan and a big pusher when wheelin. I usually don't get over 195 with the electric running.

16" puller, 2000cfm. SInce I already have it and built mounts for it, I'll probably just add another one (pusher) to effectively cover more of the radiator. And, a second relay 10F higher.

What transmission are you running? There's a lot of heat soak that occurs between the engine and tranny, so try cooling the tranny more effectively and see how that effects the engine temps.
HTH, Joe

I run a manual NV3550.

Any tips on bleeding the cooling system? I've never had a problem in the past.

In the past with my 289/302s in my mustang I found that having the coolant flush T adapter in the heater hose helped bleed the air really well. Ive really never had an issue with burping the system, but having that T always helped get a lot of the air out. If you have an overflow tank, make sure you have a good cap and there is coolant in that overflow, when the engine is hot then parked, as it cools down the coolant from the overflow will get sucked into the radiator.

You also said that you ran it for 20 minutes at 3000 rpm? Thats a lot. Why dont you shift? That alone will build a lot of heat for any system unless your moving at atleast highway speeds. I very rarely turn over 2000-2500rpm when wheelin, unless snow bashing. Also one thing to check is to see if it's running lean. That causes heat build-up.

3000 was max. 2000-3000rpm for 20min or so. I worked in engine dyno cells (production car / light truck / gas) and higher engine speeds required less cooling. More of the heat escapes through the exhaust with higher engine speeds and there is less load on the motor.

I'm worried about being lean..... idle speed was 1500 when engine temp was 220. At 180F, idle is 800. And, the motor dieseled / ran backwards for 2 seconds when I shut it off at the high idle speed. And, I burned the exhaust gasket!

All in my first time out!

sounds like fuel mixture and timing to me.

Honestly.... I havent' checked timing since I bought the rig. And, the PO didn't know compression ratio or any camshaft specs. And, I jetted down 2 sizes since I'm over 6000 ft and the truck was built for 30 feet.

302. 195cc AFR's. Roller cam. Full length headers. 600 Holley. MSD distrubutor with adjustable(?) vacuum advance. Daily driver.

Timing recommendations?

I checked the timing.... 26 at idle!! And, the mechanical advance bushing / nut had fallen off. Thank god the springs were the stiffest that MSD sells or I would have had even more timing issues.

I have no idea why the engine builder used those springs, but it might have saved me from even more of a meltdown.