71 302 V8 Wont stay cool.

[Landscapepoke]

Hi Everyone. Im new to the forum and this is my first post.

I purchased my 1971 Bronco back in August of 2015 from the family that my dad sold it to back in 1976. I have spent all last year tearing out the engine. had it cleaned up and the pistons re bored. I put it all back together with a friend and got it running back in July of this year.

Problem is I can not keep it from overheating. It over heats the most when sitting still. If I am driving down the road its ok. But if I let it sit and idol for more than 15 min, the minuet I stop and turn it off, pop goes the overflow cap on the radiator fluid overflow tank.

I replaced the water pump when I rebuilt the engine. Have the same fan blade on it that it came with. Put a new 3 core radiator in it, new hoses and a new thermostat. I have a fan shroud but its not much of a shroud. as it only has a top portion to it. I have 50/50 mix in it. Fan blade is on correct, it is pulling air through radiator.

I have read where the timing could cause extra heat to build up. I have it timed to just as low as I can go before it stalls out.

I've been told that I might have put a seal/gasket on wrong/backwards to block the water flow in the intake manifold??

I have also been told that there could be a tiny scratch on the bottom of the heads and it is letting heat into areas that it shouldn't go. Has anyone ever experienced this.

The oil is not milky so I know the head gasket is not blown and I had the radiator fluid tested to see if there were gasses getting into it. These two fluid checks have come out negative.

Short of pulling the heads off and putting new head gaskets on and refinishing the bottoms of the heads, I really would like to drive it this fall and winter.

I dont know if I have enough room to add an electric fan to the front of the radiator.

What am I missing or could I do. This is the first engine I have ever worked on in my life so I am new to the lingo and what to look for.

Thanks for your suggestions.

 

[5001craig]

Post the part number for the water pump you installed.

 

[Timmy390]

If your head gaskets are on correct, thy should be sticking out like this on the front. Both sides D and P

Add a proper shroud as that will help pull air through the radiator at idle.

Tim

 

[B RON CO]

Hi, I think your timing is off. If you have a timing light set you timing with the vacuum to the distributor pulled off and plugged. Try about 8 degrees BTDC. If you don't have a timing light advance the timing ( clockwise ) until the engine just starts to knock when you drive uphill in second gear, and retard the timing until it won't knock at all. Good luck

 

[DirtDonk]

Hi Everyone. Im new to the forum and this is my first post.

Well first of all, welcome to CB.com then!
Now, on to your issues...

I have spent all last year tearing out the engine. had it cleaned up and the pistons re bored.

Any particular reason you had it bored over? And how big did you go? Anything over .030" you should have the cylinders sonic checked. Did the machine shop do this?
Granted, this is a bigger issue on the 351's than it is on the 302's, but the concept is the same. A too-thin cylinder wall will cause localized overheating, promote steam pockets in the coolant, and just generally mess with things.

And, as said already, double check your head gaskets. Common issue.

if I let it sit and idol for more than 15 min, the minuet I stop and turn it off, pop goes the overflow cap on the radiator fluid overflow tank.

But what temperature does the gauge say? Are you in fact overheating, or could your radiator cap just be too weak and letting too much go out through the hose?
Verify with either a thermometer stuck in the coolant or a modern IR thermometer on different parts of the engine and cooling system.
Does it pop the cap immediately, or does it take a little time? Remember that the coolant "heat soaks" after the coolant stops circulating, so it's a given that the gauge temperature is going to go up after shutting an engine off. It's just what happens at the top of the engine.
Once this heat soak gets to a certain point it can continue to build pressure and the cap might be at the edge and letting coolant out.
Make sure you have a good new cap, and maybe even check the pressure rating to see if it's stock or not. If it's less than stock (say 12psi vs 14psi as an example) it might be part of the issue.
I don't remember what the stock rating is (13psi maybe?) but you can check.

I have a fan shroud but its not much of a shroud. as it only has a top portion to it.

Well, as important as a shroud is, I'm not sure it's going to cause the problem you have. Lots of people run without shrouds and don't have cooling issues. But if you're borderline anyway, it might make a difference.
It's at the low rpm that you're running at idle that's not letting the fan do it's job the best it can of course, but not sure a shroud is going to cure the overheating.
If you are indeed overheating that is.

I have read where the timing could cause extra heat to build up. I have it timed to just as low as I can go before it stalls out.

You're going the wrong way. Usually too little timing causes more heating issues than too much. So advance it like B RON CO was saying to see what happens.
And you don't have to use your idle speed as any kind of a guide. That's what the carburetor adjustments are for.
Set the timing at whatever you want, then re-adjust the carburetor's idle and idle-air screws until things are perfect again.

I've been told that I might have put a seal/gasket on wrong/backwards to block the water flow in the intake manifold??

Yep, unfortunately true. But it's also true that a particular part number from a particular big name brand also doesn't seem to work well on our engines. I can't remember the details, but seem to remember it's more of a leaking issue than a cooling issue.
Many here have run afoul of that though, so you should hear from them about it soon.

I have also been told that there could be a tiny scratch on the bottom of the heads and it is letting heat into areas that it shouldn't go. Has anyone ever experienced this.

Never even heard of it. Doesn't mean it can't happen of course, but I've never heard of or experienced it.

I dont know if I have enough room to add an electric fan to the front of the radiator.

I wouldn't do anything permanent in that regard yet. Even though I'm a fan of electric still, the mechanical fans pull more air at higher speeds still. Since you're having the issue at idle though, maybe put a big-ass fan in front of the radiator and just run it in the driveway to see if it makes the difference. If so, then start thinking about an electric fan for the truck.

But I would get back to the timing first, before doing anything else. Then jump on to the bigger things.

Good luck!

Paul

 

[Rustytruck]

Did you put the thermostat in in the right direction. Flat bottom end with copper slug goes into the intake manifold. rounded bail end into the radiator hose adapter. if the thermostat is in backwards it will overheat before the thermostat opens and it will close too soon when the engine is stopped. I would also recheck the part number on the box that your water pump came in to verify it isnt reverse rotation pump.

 

[Rustytruck]

Head gaskets are usually marked front meaning closest to the radiator. When you put the head gaskets on the front, it is always the front on the gasket and that means one gasket will be pretty side up and the other gasket will be pretty side down but the front will always be the front. Look for the installed gasket tabs in photo from Timmy390 above. You can see the protruding gasket right above the oil filter. protruding gasket should be the same on the passengers side. Timmy390 thanks for posting the picture.

 

[elan]

Buy a heat temp gun. I use mine all the time. Point and pull the trigger. Gives an instant reading. This way you can check your radiator all over, the engine in different spots and the radiator hoses. All within five minutes.

 

[Landscapepoke]

If your head gaskets are on correct, thy should be sticking out like this on the front. Both sides D and P

Add a proper shroud as that will help pull air through the radiator at idle.

Tim

Yep. Thats what they look like.

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[Landscapepoke]

Here is my tab. Same as on the P side.

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Yes TSTAT installed correctly.

Trying to locate water pump info.

Had a machine shop work on the engine. Bored the pistons to 030. Had this done as I had a test on the engine and was told the #4 cylinder was at 50lbs of pressure.
Here is the before and after.

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Temp gauge says 200-210 but after about 15 min. it climbs to 220 230. I did a pressure test on the old radiator cap and it maxed out at 13 lbs then bled off to 12 or 12.5. So I replaced it with a new cap and it holds pressure at 13 lbs.

Had an IR thermometer on the TSTAT housing. It floats between 180 and 210. When it gets to 210 it goes back down to 180ish. Shot the Radiator also. The upper D side inlet is hot 210ish the lower outlet P side is cooler at around 190. The inlet hose to the radiator gets so hot you cant even touch it.

The Cap to the radiator does not blow. Its the cap to the overflow. Pretty much immediately after I turn the key off, it starts moaning and shooting fluid into the overflow. after about a min. the overflow cap pops and steams.

Here is the fan shroud I have on.

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Here is the one I was wondering if I should get.

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Ok I will readjust the timing back to where it was. I marked it so I should be able to get it back. Dont have a timing light unfortunately. Dont know if I would know how to read it! Im a big time rookie!!

A few more pics.

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Me back in 1975 taking a lunch break.
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Same bronco today.

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Let me check tonight on that water pump.

Thanks all for your help.

 

[Landscapepoke]

Post the part number for the water pump you installed.

Purchased my water pump at O'reilly's.
Their part number is MWP 58-222
I looked it up on line and it says it is a Master Pro water pump.

I dont have the box it came in as I installed it back in May. Is the part number on the pump somewhere easy to get to to see if it really is this pump?

 

[Rustytruck]

part number says its for a 67 mustang so it should be the correct rotation for a stock bronco 302.

 

[jckkys]

The fan shroud you're thinking about is for some other vehicle, IE not an early Bronco. The one you have is correct. Think about what ignition timing does. It initiates combustion. If this occurs too late the combustion is continuing as the mixture is passing through the exhaust port heating the coolant. You want the spark to occur as early as the engine will tolerate. This varies from engine to engine. Stock small block Ford engines usually can take an initial timing of 15-20 degrees. The '71 302 with 8.6 to 1 compression is no exception. Some people run full intake vacuum to the vacuum advance solely to keep the engine cool at idle. With adequate initial timing this is unnecessary and the ported vacuum source is recommended. Read this;http://vb.foureyedpride.com/showthread.php?22229-The-Ultimate-Duraspark-Distributor-Timing-Guide. The Duraspark title is irrelevant, because point distributors have the same timing mechanism. In both cases a 10 degree reluctor advance slot helps a lot, to allow more initial advance.
You may also want to go to a radiator shop. These professionals deal with over heating engines every day. No one has more experience. Listen to their diagnoses.

 

[Landscapepoke]

The fan shroud you're thinking about is for some other vehicle, IE not an early Bronco. The one you have is correct. Think about what ignition timing does. It initiates combustion. If this occurs too late the combustion is continuing as the mixture is passing through the exhaust port heating the coolant. You want the spark to occur as early as the engine will tolerate. This varies from engine to engine. Stock small block Ford engines usually can take an initial timing of 15-20 degrees. The '71 302 with 8.6 to 1 compression is no exception. Some people run full intake vacuum to the vacuum advance solely to keep the engine cool at idle. With adequate initial timing this is unnecessary and the ported vacuum source is recommended. Read this;http://vb.foureyedpride.com/showthread.php?22229-The-Ultimate-Duraspark-Distributor-Timing-Guide. The Duraspark title is irrelevant, because point distributors have the same timing mechanism. In both cases a 10 degree reluctor advance slot helps a lot, to allow more initial advance.
You may also want to go to a radiator shop. These professionals deal with over heating engines every day. No one has more experience. Listen to their diagnoses.

Thank you.

 

[Broncobowsher]

The picture of the fan is a tiny thumbnail, I can't get a good enough version to see it and how you have it installed. It is possible to flip a fan over and bolt it on wrong. It will still be a correct rotation fan, but the scoops on the blades will be wrong and it will only flow a tiny fraction of the airflow it should.

 

[Timmy390]

That shroud on the truck is different than the one you posted the thumbnail of saying "this is the one I have". The on on the truck is not stock. It appear metal. Not saying it will not work just pointing out apples and oranges.

Check the fan depth in the shroud. The fan needs to be "up in there"

Tim

 

[tirewater]

The '71 302 with 8.6 to 1 compression is no exception.

Not sure if it matters much, but his compression will be higher given the .30 over flat top pistons shown in the above photos.

First thing though, get a timing light. They're not that expensive and they're easy to use.

 

[jckkys]

To clear up some of above concerns I looked at your photobucket images. The 2nd photo looks to me like the fan is installed correctly. The shroud you have is a metal version of the plastic OE design. It would work as well. The pistons selected by the machine shop would determine the compression ratio. The combustion chambers are 58.2cc in '71 302s. With that and your receipt the shop can determine the compression ratio. For timing it's of little relevance. This is a good aid in setting the timing;http://www.fordmuscle.com/archives/2000/03/timing/index.shtml.

 

[Landscapepoke]

Thanks everyone. I really appreciate your help and thoughts.

Pretty sure the fan is on correctly. I put a piece of paper in front of the radiator and it sucked the paper up to the radiator.

I have a 5 blade fan, would a 7 blade fan be better/ create more air flow?

I am headed to the radiator shop tomorrow to talk to him. Great idea that I never thought of.

 

[Landscapepoke]

Well I talked to my radiator guy. He looked up the radiator he sold me and said it was a heavy duty 3 core. He says its an air movement issue. I showed him a few pics on my phone but they were too small to notice what he was looking for. He said the fan blades need to be on the outside of the shroud just a little bit for the air flow to work right.

Here are a few pics I took today.

Would a 7 blade fan be better? Would it pull more air?

A pic of the new pistons and the markings on them. They say .030

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