3 thoughts/Ques on 351 cooling?

[Scott M]

i've got a 72 reman'd 351w block (92'). have a 4 core rad new in 92, and holes in the hood scoop for venting. i've always had cooling issues when it gets hot, even just on hiway and city driving, mainly city when i'm low speed or idle.

just did a new water pump, new 6 blade flex fan (replacing stock 5 blade), new balanced 180 thermostat, new 50/50 coolant, and Walker949's cooling mod to the manifold (only i used two 1/4 " hoses instead of 1 3/8"). cooling is better but still steady at 190+ or up into the 210 mark intermittently.

I've talked to other guys running hot 351s and can stay at 170. so, this got me thinking:

1. i'm running the 302 water pump. is it possible this makes a difference?
2. the radiator is setup for a trans cooler, but i run a manual, so its empty. so could that affect the cooling (seems impossible to me)?
3. did different year blocks have any internal differences that could contribute to this?
4. lastly, my inner fenders are uncut, but have most guys cut them to get more air flow, which has made the diff.

 

[Skidmark]

Cant answer specifics, but do have some tricks you could try.

Try adding more distilled water to your coolant water carries more heat away than the antifreeze. I run around 75% water to 25% coolant in the summer. Try some water wetter, It brought me down about 7 degrees.

Throw in a lower temp thermostat. I was always overheating with a 180. I switched to a 160 and haven't climbed above 195 yet. Tried just the other day. 100 degree day idling with sloooowww driving. Still couldn't do it.

These are very quick and very cheap things to do. It may not seem like you'd gain much, but before I did these simple things I was constantly climbing over 210.

I'd try these methods before you get too radical.
jake

 

[74bronc]

i highly recommend cutting the inner fender wells, as long as you aren't a bronco purist that only cuts the minimum amount necessary. Cutting mine made a very noticeable difference on my 351W. I was driving it up the cajon pass a few weeks ago in socal and it was 95 degrees ambient temp and I never went over 200. then drove it across the desert in the same heat and never went above 190. very manageable temps

 

[72Sport]

i've got a 72 reman'd 351w block (92'). have a 4 core rad new in 92, and holes in the hood scoop for venting. i've always had cooling issues when it gets hot, even just on hiway and city driving, mainly city when i'm low speed or idle.

just did a new water pump, new 6 blade flex fan (replacing stock 5 blade), new balanced 180 thermostat, new 50/50 coolant, and Walker949's cooling mod to the manifold (only i used two 1/4 " hoses instead of 1 3/8"). cooling is better but still steady at 190+ or up into the 210 mark intermittently.

I've talked to other guys running hot 351s and can stay at 170. so, this got me thinking:

1. i'm running the 302 water pump. is it possible this makes a difference?
2. the radiator is setup for a trans cooler, but i run a manual, so its empty. so could that affect the cooling (seems impossible to me)?
3. did different year blocks have any internal differences that could contribute to this?
4. lastly, my inner fenders are uncut, but have most guys cut them to get more air flow, which has made the diff.

If you have a 180 thermostat it starts to open at in the high 170s and is fully open at 210. Sounds like it runs hot enough to completely open the thermostat "intermittently". Sounds like it is doing what it should for that thermostat. I would guess that a 92 was designed to run with a 195 thermostat, starts to open in the low 190's and is fully open at 220+. Doesn't sound like it is running as hot as it was designed to. Running less than 180 makes for rapid cylinder wear.

 

[Scott M]

72 sport, its a 72 block, reman'd in 92

. guess my main concern was if the 302 pump was somehow an issue?

 

[72Sport]

1972 Ford Custom with 351 Windsor 192-195 Thermostat oem. Same as 72 Bronco with 302 per Napa on line.

 

[Scott M]

anyone w/ a 302 pump on 351w w/ not cooling probs?

72sport: i understand factory may call for high t-stat. but, my understanding is that the fact remains that regardless of the t-stat the motor should be able to maintain that temp if everything is correct. so why the hell isn't mine? only other options are water wetter and fender well cutting as far as i can tell. but there seem to be guys who are stock and don't have any problems. so what gives.

 

[Skidmark]

Hey 72sport, curious as to why temps below 180 cause cylinder wear?

My running temp is right around 180-185 so I'm not worried about being too cool, but I've heard people say the same thing about the cooler temps causing premature wear.

How does too hot of a coolant flow affect cylinder wear?

 

[broncnaz]

You may want to check out bronco driver issue 12 there was an article about closing up the gaps between the top and sides of the radiator to seal against the hood and core support. they used aluminum sheet metal and weather strip to seal it up. it seems that hot air from the engine bay is drawn over the top and sides and back through the radiator so sealing it off from the engine bay can reduce temps. the article tested this on a 302 with AC the hottest it ran with the ac on or off was 190.
There's no differance between a 302 water pump and a 351 water pump they are all the same. Although some of the aftermarket high flow pumps work pretty well.
A couple other things to consider 1 your head gaskets could have been installed backwards. 2. ingintion timing to far advanced 3. your running lean 4. make sure you have no leaks in your radiator and your cap is good small leaks or a bad cap will make it run hot also.

Your auto radiator should really not make a differance it just holds a little less water than a manual radiator

As for engines running less than 180 wearing the cylinders faster part of the reason is that the cylinder doesnt expand enough below 180 so it stays on the small side while the piston is heating up and trying to expand so the clearances become tighter causing wear.

 

[wildbill]

;D ;D ;D The water pump are about the same just different outlets one left and the other right. I have run the 351W since 74 and never had a heating problem and I run a 160 with stock rad. and fan no shroud. You didnt say what bore if it go's over 50 then that will cause you to run hot. Also if you run a 289/302 cam in a 351W it can make it run a little hot but will work. Good luck. Bill %)

 

[Skuzzlebutt]

Lose the hood scoop! Seriously. A forward facing scoop like the one in your pics increases air pressure in the engine compartment which means there will be less air flowing in thru the radiator. A reverse scoop, like on the cowl induction style hoods are great for letting hot air out and ergo, more cool air in thru the rad. Bill Stroppe came to this same conclusion 35 years ago.

 

[72Sport]

Hey 72sport, curious as to why temps below 180 cause cylinder wear?

My running temp is right around 180-185 so I'm not worried about being too cool, but I've heard people say the same thing about the cooler temps causing premature wear.

How does too hot of a coolant flow affect cylinder wear?

Pistons are not round at room temperature. They expand as they get hotter. They are designed to be round at operating temperature. The thermostat is supposed to keep the engine operatiing in the proper temperature range. If the piston is not round when under load the pistons have too much room to move in the cylinders and cause rapid wear on the cylinder walls. At least thats the way I understand it. Every book I have read says that too cool is not better because of cylinder wear.

 

[Scott M]

some interesting nuggets there...

the hood and gap around the radiator are worth a try.

FYI. its just a stock 351 (so its not bored 50 over or anything). i've got a good shroud. its not too lean, and timing is good.

i'll try some of those things and see what happens. thanks fellas

 

[72Sport]

You may want to check out bronco driver issue 12 there was an article about closing up the gaps between the top and sides of the radiator to seal against the hood and core support. they used aluminum sheet metal and weather strip to seal it up. it seems that hot air from the engine bay is drawn over the top and sides and back through the radiator so sealing it off from the engine bay can reduce temps. the article tested this on a 302 with AC the hottest it ran with the ac on or off was 190.

Wow! I thought no one read the article. It is actually on page 59 of Bronco Driver #12. I spent a couple of weeks gathering info for that article and a lot of time, money for thermocouples and gas. It does work very well. At the time of the article was written I was running 57 degrees total advance due to a missing stop inside a new vacuum advance. It runs cooler now than what is stated in the article. It has to improve things enough so that a 351 will run as cool as a stock 302.

If you look at your "new" car you will see it is sealed everywhere around the radiator to keep all the cool air going through the radiator rather than around it.

K-S used to sell a baffle to mount on top of the radiator to slow down the re-circulation of hot air from the engine side of the radiator.

I did the research because I was planning on selling a kit. Unfortuanately I couldn't find two Broncos the same in the radiator area not to mention lifts etc. Seems that something was always bent on someones Bronco so I gave up. The ups driver would have been very busy returning stuff. I still have enough rubber to do a couple of Broncos. The rubber just slides on and can be easily removed. The removal of the hood prop rod makes things easier along with the little plate for the safety latch. I rotated it 90 degrees when I added a remote latch as mentioned in the article.

If someone wants to try it I will sell the rubber for a $1.50 a foot plus freight.

 

[72Sport]

72sport: i understand factory may call for high t-stat. but, my understanding is that the fact remains that regardless of the t-stat the motor should be able to maintain that temp if everything is correct. so why the hell isn't mine? only other options are water wetter and fender well cutting as far as i can tell. but there seem to be guys who are stock and don't have any problems. so what gives.

I don't think 210 is hot. With a 13# radiator cap and 50/50 coolant it will boil at 265. Getting a cooling system that will always run a constant temperature no matter what the outside temperature is impossible. I have a boat which uses a lake for a radiator and it will vary 15 to 20 degrees depending on what I am doing at the time. It has a 145 degree thermostant. The thermostat only controls minimum temperature. If the others you are talking about have stock gauges they never see it. My stock gauges were reading at least 15 degrees low.

I think fender cutting reduces strength in the front end. There isn't much strength left when the fender wells are missing. Besides I am one of those purists who doesn't own a sawzall. I have never tried water wetter but I know it has been around for at least 45 years. Like Broncnaz says read the article in Bronco Driver #12. I know it works. Its easy to do and can easily be removed if you don't like it.

 

[sbingham2]

The EB manual states that there's no danger unless the pointer goes to "H" and stays there (230*). If you're running between 190 and 210 and your cooling system isn't boiling over, I don't think you have anything to worry about. Honestly, is it worth the fuss if it's at least consistent in its range and you're not actually overheating? You definitely don't want to go below 190, cooler temperatures increase cylinder wear and exhaust hydrocarbons.

If you're deadest on messing with it, here are some things to think about.

- Check your timing and advance, retarded ignition timing starts the combustion process later, allowing it to continue out the exhaust, which heats the cylinder head.

- A rich carb idle circuit can contribute to low speed over heating. The rich fuel mixture tends to keep burning as the exhaust leaves the port, which heats the cylinder head.

- Electric temp gauges can indicate higher than actual temperatures if the ground circuit is not optimized. A bad ground can cause the gauge to read up to 15 degrees higher than actual. If you have a multi-meter and want to test your grounds, let me know and I can provide some pointers. EB's came with electric gauges.

- Make sure your belts aren't slipping and that your coolant hoses aren't collapsing under speed.

 

[72Sport]

72sport: i understand factory may call for high t-stat. but, my understanding is that the fact remains that regardless of the t-stat the motor should be able to maintain that temp if everything is correct. so why the hell isn't mine? only other options are water wetter and fender well cutting as far as i can tell. but there seem to be guys who are stock and don't have any problems. so what gives.

Here is what GM has to say about improving cooling on RV's in the 90's:

1. "Cooling can be improved by inserting filler panels between the outer vertical side edges of the radiator and the grille. This will prevent "ram air" from by passing the radiator and exiting through the front wheel housing area."

I think filling the area between the radiator and radiator support is more feasible with a Bronco. Some of the holes in the radiator support can be plugged also. Force the air to go through the radiator not around it.

2. "A flexible air-tight seal must be provided between the upper radiator support and the body to aid idle cooling and prevent hot air recirculation."

Prior to finding this article I had done the same thing with my Rv after going from a 4 core to a 5 core radiator. I would get very hot very fast if I let it idle. A rubber seal along the radiator support and above the radiator is more feasilble.

 

[TOFIC]

Cooling Problems

Scott

Feel for you man had a few of your problems myself. Some advice from the TOFIC if I may.

Get the water pump for the motor not the year and flavour of the Bronco.
Check the cooling channels in the front of the Intake manifold next time you have it off. Mine had some casting material in them that cut the flow by 50 percent.
Next is air flow, this is the big one.
Bronco were not DESIGNED for V8's (see 66 and 67 only came with 6's) Therefore the engine compartment is cramped comparitively speaking. The issue is not getting air into the compartment it is getting it out. hood scoops cutting the fenderwells and other vents are these cures. When you attack this problem think about getting the air out!! When I did my 351 I put a huge vent in front of the windshield. This worked!! so attack the air problem not the cooling problem

TOFIC