Thanks, Lee. I'm still waiting to get the dimensions of the two possible fan shronds available, then I'll pick a flex-fan & spacer to match it as best I can. I'll swap down to a 180 from a 195 stat when the truck gets back. I already have an electric pusher fan in front, on the passenger side, since the middle strut wouldn't let us mount in the middle. I've considered adding a second one. The new radiator is definitely a 4-core, and the timing seems right. The mechanic who installed the new engine a few months back timed it by the book, about 4 to 7 BTDC, as he recalls. I am running 50/50, and my local speed shop guy runs water wetter with 50/50 in his 351M, with good results. So far the temp here is now near 90 and climbing; my driver says it's running 210-215 but has had only very short "idling stops" so far. Why is the blade mid-point important for the edge of the fan shroud? Seems like having a shroud go back further wouldn't make a difference in how much air it pulls through....??
Gid

 

Lee & Gid, I have rolling around my head that the t-stat is for heat in the wintertime and not for any thing for summer. Not suggesting it but you could run the engine in the summer with out one with no problems. The t-stat only opens to allow the water to circulate after it reaches the 180, 190 or whatever.

I think that after an experence that I had with one, the shroud is much more important in the summer.


John
jowilker

66 F100s
In the still cool hours of the night, you can hear chevys rusting away.

 

Does the water temp go down when you go down the road at 55 cruising. If it does this would make me believe it was the shroud. If it was the shroud the truck would get hot while idling because the fan can't pull air through the radiator. When you get going down the road the air coming in through the front of the truck flows through the radiator keeping it cool.

 

Update: Engine temps ran higher again because of 98-degree weather. Got up to 225-230 in a ten-minute traffic snarl-up.

I was also quite surprised that removing the thermostat a while back did nothing to help this problem, since I've done that successfully many, many times on Dodge 318's, Ford 302's, & dozens of others for 30 yrs. It actually got worse, and putting the 195 stat back in lowered the engine idle temps ten degrees at least. An earlier Forum archives search mentioned this, and I'm convinced now that the coolant can indeed move too rapidly thru the system to get adequately cooled by the fins. I'm hoping a new 180 stat will help more.

Engine temps are definitely far worse problem at idle, even short idling. Getting moving again drops temp right away. I agree that shroud seems to be a factor, but it puzzles me that an electric blower in front of the radiator (though only on half the radiator) doesn't overcome the lack of a shroud.

The earlier post about a shroud source (www.autokrafters.com) was invaluable after my long unsuccessful local search -- these are VERY nice, knowledgeable and helpful Ford people with wide selection of old Ford parts, new & used. They have one possible shroud available & patiently measured and gave me detailed size & specs to check for fit. Will know more about fit early in AM after careful measurement of fan, radiator bolts, etc.

Couldn't give fair try of earlier recommendation about idling higher. Driver got very little service work done due to scary-looking leak at rear hub; probably OK -- a new Jasper rear was installed a few wks ago and the hub nuts just needed re-torquing, we now think, but it blew much of the day.

The saga continues at first light....thanks for the help!

Gid

 

In order to control wear, your engine needs to run a coolant temperature of at least 160, 180 is preferrable. Beyond 180, wear continues to be reduced but at a much slower rate until, of course, poof! Running without a stat in the summer will allow that wear time from 'cold' to 180 to be way too long.
The other thing is flow, stats reduce the flow thru the radiator. Why? Because the coolant needs time flowing thru the radiator to release its heat. I know it sounds a little backwards but a trick many vintage car owners (w/o stats) use is to stick in a fender washer (drilled out, trial and error) in the radiator hose to slow the flow.

Lee
1965 F100 short box styleside

 

The reason for not burying a stock fan into the shroud is that once past the blade, it is intended that the air is thrown out all around in the engine compartment. That is why they have those weird tips to scatter the exhaust air around the engine, most of which goes down towards the pavement. Throwing the air all around the engine bay keeps it all relatively the same temp rather than having hot spots.
In order to pull efficiently, the fan needs to be encased to max out its drag. If it isn't snugged into the shroud, then it will cheat and pull air from the easiest source which will be anywhere but thru the radiator fins.
If you go with an aftermarket fan, be sure they tell you were they want you to place the blade in the shroud.

Lee
1965 F100 short box styleside

 

We put a 180 stat in this morning. Weather will be 92 degrees, so it should be a reasonable comparison with the 195 we had in yesterday. (UPDATE: the driver just called, says it seemed to run a bit cooler (180 - 210) at first, but now that it's 92 outside it's hitting 220 at the service stops. I think we still may find that this is an improvement by the end of the day).
The dimensions on the "only fan shroud in the whole world" don't look like a dead match, but I ordered it UPS'd here anyway. The 21" fan opening in the shroud is offset a couple of inches toward the pasenger side, and our nearest eyeball estimate is that our 16" fan is only an inch at most off the center of the radiator. However, with a big enough hammer, meat cleaver and some pop-rivets, we can probably modify it to work OK. Looks like it'll take some short, maybe half-inch spacers behind the shroud to get the opening even with the stock fan blades, and if we do a flex-fan later it'll need some correction.

I believe Lee is right about the flow rate. Also, I didn't realize that getting up to operating temp more slowly could affect engine wear; I assumed most start-up engine wear was due to "dry" cylinder walls & rings. I may have shortened the life of a few engines inadvertantly. The fender washer trick is slick, and would make for a very even, non-jerky flow of coolant. Sleeving the inside of the hose with a smaller size, or two, might be easier for the fumble-fingeredHowever (and believe me this is strictly an amateur guess) since the engine temp depends on so many variables -- outside temp, type of driving, rpm's -- it seems to me that a fixed flow rate might not be as good as one controlled by a thermostat....and also for the reasons Lee mentions above. If I had an old non-thermostat system I'd probably scratch my head and try to rig some in-line thermostat (maybe two back-to-back thermostat housings in one of the hoses, figuring that a flow that varies with the demands of the engine is better overall. Of course, if I'm so smart, how come I'm the one looking for help??

Gid

 

Just something I'd like to add here. Make sure you have your electric fan hooked up correctly. My friend had installed one on his 66 nova, and he had the wires backwards, which caused the fan to spin the opposite direction. Basically making a "pusher" fan into a "puller" and it was pulling air through the raidiator and pushing it out the front grill. When he had it like that, it was running about 225. He was so frustrated because it was running even hotter than before he installed the fan. I realized what he had done, and all we had to do to fix it, was swap the two wires around. Just thought I would mention this, because it can be easy to mess up.

Also, I have a new 400 in my 1980 f-150, its got a 4 core rad, 180stat running 50/50 mix. Yesturday it was 95 degrees here, I ran the truck all day and never saw anything above 195. Was your 400 overbored? often times when 351m/400 engines are overbored too much, they will run too hot. These enignes have relatively thin cylinder walls. Mine is .030 over. I've been told any more than that will cause them to run hot.

Good luck!!

SteveT

 

Good idea, Steve, and one I hadn't thought of. However, I just called my driver and had him stick a piece of paper behind the electric fan and it is pulling air through the radiator (toward the engine) very strongly. I just called the local Ford dealer again, and they told me they don't think the remanufactured engines they sell are usually overbored. I explained the whole problem, and he doesn't think 220-230 is any kind of a problem, that "all the new engines run this hot." Maybe I'm just too old for new ideas, but I'm still going to keep trying to get that engine temp down, even though at 220-230 we haven't yet seen steaming, after-running or engine stalling. Thanks for the idea -- I'm learning a lot here.

 

>I think I'm close to fixing
>a chronic overheating problem on
>my '78 F-350 flatbed.
>The 351 blew aqnd I
>replaced it with the dealer's
>only replacement engine, a 400.
When you got the replacement motor, was it new or
rebuilt? If it was rebuilt, do you Know if it was bored or not? If it was bored more than .030 over, these motors have a tendency to run on the warm side.

 

Just a thought but with all you`ve tried i wonder if the cooling passages in the block or heads may be plugged with something.Perhaps during or causing the rebuild.

 

Gid, sounds like you need to narrow down the problem between the engine generating too much heat or the cooling system not being able to reject heat properly. Before the 351 blew up, did you have overheating problems then? How many miles are on the replacement 400? It could be a really tight motor generating more friction than normal until it gets broken in. Is it slow to crank over when hot? Have you checked for tiny bubbles in the coolant, it could be a leaking head gasket(s). Also, there might be a vacuum leak somewhere causing the mixture to lean out. The other scenario is the overbore is too large and the thin cylinder walls are running hotter than normal. I you have to live with a hot running engine, you might want to throw in a 160 degree thermostat to give you a little extra margin. Don’t worry about running too cold with a 160 degree, especially if you’re in a warm climate zone. That’s the temperature at which the valve begins to crack open, it’s not fully open until around 15 degrees or more hotter. It will warm up to it’s operating temperature fast enough, a closed 160 thermostat is the same as a closed 200 thermostat, it just opens sooner.

 

UPDATE: After a full day with the 180 instead of the 195 stat, the only significant difference was that it cruised at about 180 instead 190, but at each short idle it still went up to 220. The driver THINKS it seemed to reach 220 FASTER with the lower stat, but that sounds pretty weird to me.

To answer the recent postings: The old 351M never overheated, even with the old 3-core radiator. The "new" 400 is from Ford and is, if I understand correctly, remanufactured rather than rebuilt (i.e., they replace all the internal parts even if they don't look bad). It's been in the truck for several months, maybe 4 or 5, and running 5 days a week mostly in suburbs or rural areas. I'm guessing it has 8 - 12K in mileage and more hours than normal, so it should have been well broken in over the winter. I don't know about the overbore; is there some stamp or code somewhere that will tell me? I've looked at the coolant a lot and never noticed little bubbles, but I'll look at the overflow tank very closely in the morning. I'm fairly sure there's no vacuum leak, since with this setup (where we use engine vacuum to maintain vacuum in the wastge tank) a leak shows up on the vacuum gauge and makes the 2" suction hose work very poorly -- and makes the driver curse a lot at each stop. He's very adept at tracking down the tiniest vacuum leak that makes his work difficult.

If Ford messed up this rebuild and restricted a water passage, I can't figure out how to look for it, though it would explain a lot. More likely it's an overbore problem, though, I imagine.

The observation that a closed 160 is the same as a closed 180 never exactly occurred to me, but of course it's absolutely right. And then it suddenly occurred to me that an open 160 is the same as an open 180 or 195 -- so assuming that when my truck runs all day at operating temperature, the thermostat (whichever type it is) is largely open all day. Which explains why it ran at the same max temperature (220) today with a 180 stat as it did yesterday with a 195. An open stat is an open stat, regardless.
So I probably wouldn't drop that engine temperature even if I go to a 160 thermostat. At least, that's how it seems to me.

My brain is beginning to fry from thinking about this too much, so I'm going out to dinner and try to think about something else for a few hours.

Thanks for the input!

Gid

 

Gid, your absolutley right about the thermostat. The only variation of its operation is that a 160 would only be closed when you first start the truck, once it opens, it would most likely stay open. I tried running my 400 without a stat once, it never heated up more than 165 or 170. If your running a 180 (as I am) then it would open when the temp reaches 180, then it may cool back down below 180, and close again. I dont think that would really change anything though... seeing as your truck is always running around 220, then no matter what stat you have, its always open. One other thing I wanted to mention, is that as far as fans go, you may want to think about getting a clutch fan. They tend to work more efficiently than a fan without a clutch. I've made the addition to many of my vehicles in the past in efforts to cool the temp, and it has always helped. Of course you DEFINATLEY need the shroud. The shroud is an very important part of the cooling system. It helps the fan pull air through, and also focuses the air onto the engine. I dont support the idea of the flexfan, simply for the fact that they flex. As the engine rpms increase the fan blades straighten out and reduce the pitch/angle of each blade. Which is sort of a draw back to them for good cooling. I've run them before, and always had more heat. (which doesnt mean it would be that way in every case). I think flexfans are more designed for high perfomance applications, where you would want the fan blades to straighten out, because it reduces parasitic drag from spinning the fan. The clutch fan reduces drag when reving the engine, but is fully engaged at most engine speeds. They work very well. good luck! let us know how you make out.

Note: you shouldnt have any trouble finding one at a junk yard. Its worth a shot!

SteveT

 

Just an idea, after I built my HP 302 board to .030 over I went to Autozone a picked up a Robert Shaw High Performance Thermostate. My 65 ford truck has a flex fan and no shroud and I run it all day in 110 degree wether her in AZ. The thermostate has a whole twice the size as a stock thermostate whole for better flow. My truck runs 190 degrees. Hope I was some help.