HIgh speed engine heat

Hey guys,
I need some opinions on this one...

I've been working on keeping my van running cool for quite some time now and generally speaking, its been running great!
I currently have a new, larger core rad with a front pusher fan & back puller fan , i've got a belly pan with a modified wing to ensure air is getting up into the rad and the engine itself is pretty tuned as far as timing goes..
At low speeds, (under 50mph) the van runs cool.
As soon as I start getting upwards of +60mph or hitting longer hills on the highway that demand higher RPMS, the engine starts to really heat up..
My engine is a 170.
I'm somewhat stumped. In low air-flow situations, the van runs great. In high air-flow situations at speed (highway) the engine heat climbs.. You'd think it would be the opposite.
I was thinking about adding a heavier motor Oil (10w50) or adding an air damn at the top/front of the rad to ensure air is only passing thru the rad.. But I'm kinda grabbing at straws now.

I don't have the exact temps as my temp sending unit in my van is incorrect for the gauges. (I'm still trying to find the original size of the sending units for a '65 with a 170cc)
The gauges aren't accurate but they still respond to heat.. Ie: climbing & falling ..

I love any suggestions on this one..
Jes

Ill ring in here- my 1st question is -what is your actual rear axle ratio?? Next realize a 170 cube engine when designed in our older vans wasnt really designed to run 70mph on the highways.Small cubes!.Therefore back to my 1st question?? Also=remember when we are pushing a box thru the air @ higher speeds =we are dumping more fuel in the engine to achieve the speeds we desire. More fuel = more heat (burn) =Higher temps! Rellizing this =is the crank/ignition timing set as to factory specs? What about =total advanced timing?? Whats that value also? Many parts over the years have been added =like distributor vacumn 's replaced yet usually no one ever checks the advanced timing. Is it higher than what engine was designed for?? If centrifical advance distributor is used?? whats that total advanced value? Remembering that type timing is advanced by centrifucal force overcoming some springs-ie:= worn & weaker springs=???? over time . Is the distributor changed & updated to newer type?? Now if all is the same & as designed ?? Back to not only air flow but water flow inside the engine?? Coroded inside? water flow must be controlled yet also must have time to have the airflow take that heat away too!! Also =realize this as you state = the radiator has a pusher fan & a puller fan?? Can you actually be defeating ariflow thru the radiator with that dual combination?? Very possible @ faster speeds=air is just being blocked by the 2 fans?? Looke into all & remember =pushing a box thru the air takes more fuel & =that equalls more hear generated! 

When tooling around town it stays cool but when you hit open road and cruise at sustained high rpms then it gets hot...this condition is usually caused by a timing issue. In another post you indicated upgrading the ignition system - new distributor? You might want to set your initial timing using a vac. gauge (highest reading and back off 2) and then use a light with an advance indicator to make sure you are actually getting advance at high rpm. You might want to re-think using a puller and pusher at the same time. Two opposing fans usally disrupt the airflow rather than help it. Pullers are more effcient than pushers, so after you reset the timing, if you can run with the puller only I'd give that a shot.

Hey Twinpilot001,
My rear axle is a 3.50 7.25".
Pretty much right in the middle for 170 to still give a bit of push in 1st gear/2nd but not rev too high in 3rd at speed.

Concerning the distributor, I was having a horrible time trying to get my old load-0-matic to work properly. I played around with a new coil and added electronic points but in the end, The distributor I had kept failing. After a few tow truck experiences  , I ended up converting to a DuraSparkII with a Dyna Ignition Module and inferno coil. After I installed this, I had the timing set at a shop that works with a lot of older cars. (they seemed pretty knowledgeable) There was a pretty massive difference compared to the load-o-matic but until this past weekend, I hadn't really hit the highway or driven at speed for a while so maybe the time was set too advanced?

Concerning the ADVANCE TIMING, I'm not going to lie and claim I know a lot about these old engines and in truth, i think I spend more on line researching the function of each component than i do working on my van.. So keeping that in mind, I don't really understand the difference between the ignition timing and the advance timing? From what I've learned, the ignition timing is moment in which your distributor releases spark to plugs in relation to the position of each piston on its up/down path. This is set to ensure that each piston is getting spark at the exact right time for a smooth & proper combustion. (or that's my understanding anyway..LOL)
Now where does the advance timing come into play??

Concerning the water flow or any obstructions, it should be super good.. My engine was fully rebuilt several months ago and I've swapped out the hoses & rad so there should be solid flow thru the system..

After thinking a lot about it let night, there are a few areas that I think could be causing the problem..
1) As you said, it's a small engine with a mid-size gear ratio so at higher speeds, it's going to working it's ass off.. (solution: Cruise at 60mph!)

2) The engine was most likely rebored and I've read that this can "thin" out the walls making for less insulation between each piston. ( disclaimer: Not too sure what this means exactly but seems worth noting)

3) The duel fan set up is great at low speed as the speed as the air flow is directed right up between the front of my rad and the front of the doghouse. As the air flow ups, the push/puller fan has enough force to get the air flow to travel thru the rad. As i travel faster the air flow gains more force and the bulk of it essentially blows right past my Rad (which is obstructed by my pusher fan) and blasts over the the top of the rad head in the space between the head & lid of the dog box.. Its almost like I've added the basement but no roof.. ( possible solution: remove the pusher fan and added some type of air dam at the top of the rad to ensure the only exit for the air is THRU the rad itself. Not over it..

4) Finally, ( and this is purely a guess) I was thinking about adding a heavier motor oil like 10w50 in the hope that as my engine starts heating up, the 50weight oil will not get too thin. This is just a theory as I'm not sure this will actually work as on the same note, thicker oil means more resistance in the engine which in turn, makes more heat..

Jes

Something else perhaps is an air dam between the rad and engine at those higher speeds created by the air in the doghouse not being able to escape fast enough. Have you tried running it with the Dog house open at the high end of things? Not a pleasant thing to do but would help tell the tale.

with these old engines you should be using  oil with zink there is a lot of info here .  https://vintage-vans.forumotion.com/t21122-zink-and-oil?highlight=zink

Hey Digz,
Definitely worth a shot! I'll give it a try later tonight or tomorrow and see if I notice a difference.

Also a great tip Dix..
I definitely will change my oil tmr and ensure I get one with Zink.. That thread is pretty crazy about how important it is... Kinda kills me as I literally just put about 500miles on my new rebuilt engine and I'm not too sure if the oil in there had Zink or not!! Nonetheless, I'm going to change my oil to be sure..

From what you've been describing I would think that it's a water flow problem.
If all is new you might try replacing the thermostat, maybe it's not opening all the way.

When my radiator was stopped up it acted just like that the faster you went the hotter it got. New water pump already on?

Thanks Magicbus and Econocarl.
There appears to be pretty strong circulation in the Rad when I was filling it and rev'ing the engine but I'm not too sure the last time the water pump changed but I'll check this afternoon . The thermostat was done last fall but its and easy change for the sake of ruling out problems!

Majority of all oils sold today=DO NOT!! have the Zinc in them. TThetre all designed for our roller lifter engines & zinc isnt needed in them! A Fwe racing oils have the zinc in them yet again =FEW!! I always add a Zinc suppliment additive to my oil changes-all auto parts should have -i always get mine at NAPA! Its not cheap yet neither is a cam & metal in the bearings!! 

You are right on about an air dam over the radiator. From the factory the Econolines had a dam of sorts over the radiator. That, combined with a complete bellypan, forces all air taken in from the grill and the bellypan to be directed striaght thru the rad with no other place to go. A puller fan with a shroud works the best as they do not ever restrict or deflect any air from passing thru the rad. If water flow is not an issue then airflow and timing are the likely culprits. As far as thermostats are concerned, they are designed to control the rate at which your engine reaches normal operating temperature at which point they should stay open with as little restriction as possible. ALWAYS run a fail-safe stat!

One other thing to consider is the coolant being bypassed thru your heater core, this water is not passing thru the radiator. Make sure that your control valve is closed.

RipVanArkie wrote:
One other thing to consider is the coolant being bypassed thru your heater core, this water is not passing thru the radiator.  Make sure that your control valve is closed.

Hey RipVanArkle,
Thanks for jumping in with some advice!
I'm going to mock up an upper air dam tonight and give it a shot! It completely makes sense that as speed increases, the airflow travels faster/harder looking for the path thru the engine of the least resistances... The fact that I have a puller van eating up the already limited space would mean that I'm expecting the airflow thats blasting up in front up the rad to make a harsh 90degree turn THRU the rad as opposed to flowing right over the top of it..
An upper dam should limit the direction in which the air can flow making travel thru the van the only option..
I'm hitting the road on another 1000 mile adventure tomorrow so it should be a great opportunity to test out some theories!

Concerning the theory of checking the control valve, not to sound silly but where would I find this to check that it's closed??

The heater control valve is in-line with one of the two heater hoses.

Let is know how it goes!

And you are right, we are forcing the air to go where it would not naturally flow! Even an aircooled VW can easily be cooked if you remove the sheet metal from around it.

RipVanArkie wrote:One other thing to consider is the coolant being bypassed thru your heater core, this water is not passing thru the radiator.  Make sure that your control valve is closed.

I've always though that if your heater control valve is open it was like having an auxiliary radiator.

Great conversation on this topic.

Carl, that only rings true if you have the heater fan on moving air thru the core. Otherwise, that water is just getting hotter and in some engines it is designed to circulate thru the cylinder head so that your heater warms faster, great idea but when you are having cooling issues it only raises your head temp.

New to posting on this site but I would like to weigh in on this. In the 70's I had a E100 with a 300 six and 3.50 gear all pans and shrouds in place and that van would run hot anytime I was around the 70 mph range. It just did not like those speeds