FE Head Temp

[frnkeore]

I've got a question, regard the temp range of the heads, from the back to the front of them. I asked Jay about it and he has never check it.

Knowing the coolant flow path, starting in the front of the block, transferring to the back of the block, then up to the head and flowing forward, to the outlet, it would seem that the front of the head would be, at least some what or more,  hotter than the back of the head.

Has anyone taken the temp, along the head, to see how much difference there might be? I've always wondered about that aspect of Fords cooling system. Same question for the SBF, too.

[pbf777]

     This, if you think about it, would prove somewhat complicated to execute garnering accurate information from which to draw a meaningful conclusion.       As in many manufactures including the O.E.M.'s have in instances failed to achieve proper water flow and consistent cooling values across the entire area's intended; in an example even much more recently than the FE's manufacture just google the issues of the Ford 4.6 4V Cobra heads from the '90's into the 2000's; and with several of the aftermarket cylinder head products presented over time in which a rather obvious disregard for the needs of the water jacket for efficient function was compromised for other concerns with less than satisfactory results.   

     Scott.

[frnkeore]

Thank you, Scott.
Very interesting, I didn't know about the Modular 4V problem. I would imagine that all OEM's, would have to conduct cooling system testing, be for releasing a engine and this info, would be in the engineering files, somewhere at Ford.

What I'm interested in, at this time, is how much water temp variation there is in a stock FE head, by casting #, front to back, just based on the type of cooling system flow that Ford uses. And if after market heads, such as TFS and Edelbock, improve that variation.

The block and oil, cool but, the major heat, is in the head (especially the ex area) and since the block coolant, is already preheated, before transferring to the head, I'm wondering how much that increases before getting out and back to the radiator.

Something like contact pyrometer readings at each cylinder, front to back, on both sides of the head, while under power. At a minimum, a reading on the flat surface at both the front and back.

[My427stang]

Of course I have not measured it, so if you want to ignore the rest, feel free...

I agree, tough to measure and even more would be tough to define a common rule of thumb across engines and operating parameters.  Variables that would affect front to back temps in my opinion

- head gasket material and thickness - of course a "piece" of water gets hotter as it travels the path, however, as it travels to the front of the head, it encounters a cooler area of the block up front coming from the radiator (although blocked from water flow).  In this case a steel shim gasket should transfer heat there better, making the head more stable but a .053 fiber gasket would likely be less as a decent insulator.

- pump pressure - not system pressure from expansion, but how hard the pump is pushing, and how hard the exit water flow is resisting  A higher capacity pump, as well as rpm up to cavitation point will force more movement into areas that may not flow as well with lower RPM or pressures.  This could cause or stop localized heating depending on RPM and pump design, as well as thermostat or restrictor flow

- differences in casting - I haven't looked close for this, but knowing the casting flash and inconsistencies externally on a casting, I bet no two heads are alike, even block water passages are different just comparing 390 to 428

My guess is it's relatively stable, what that high/low range for a given load and rpm may not be single digit variance, but we are not seeing #1 and #5 exhaust valves stick or require additional clearance, and even exhaust ports, although farther away from water, don't discolor significantly different

[GerryP]

It's somewhat irrelevant in nearly all applications.  F1, sure.  NASCAR, sure.  Pro Stock, nope.  There's not a lot you can do in a production application about temperature variations per cylinder or combustion chamber.  You have cost, durability, and packaging concerns.  Racing is a different environment.  In the days of NASCAR requiring production blocks, you had the era of the SBC using 18-degree heads and then the SB2.  They used a coolant tap midway on the cylinder head to help cool the exhaust part of the middle chambers.

The reason it isn't a production concern is there are too many variables that affect engine running temperatures.  Racing applications run in a very narrow RPM and load range.  Not too many race cars sit in traffic, or crawling along because one lane gets shut down.  And production engines do make some accommodation to temperature variations.  Smaller holes in the deck and the head allow for some water to move from the block into the head along its length.  Yes, the big hole is at the rear and that's where most of the flow occurs.

If you wanted to, you could put thermocouples in various points in the head and block.  Yeah, that's really kind of race shop effort, but you could do it.  That way, you would know.  After all, that's how the race shops capture the data for engine design.  But then, when you have the answer, you have to decide how extensive you are willing to re-engineer the engine to address what is probably not even a relevant concern.

[pbf777]

What I'm interested in, at this time, is how much water temp variation there is in a stock FE head, by casting #, front to back, just based on the type of cooling system flow that Ford uses.

     I think one would find that the Ford O.E.M. 'bread & butter' castings would be relatively consistent in their effectiveness of temperature transfer as the engineering is very much consistent.  The opportunity for significant differences would be in the comparison of the standard castings to those with significant engineering changes which prove often to be adopted modifications of the existing casting such as the 'Medium' and 'High-Riser', 'Tunnel-Port' and then particularly the S.O.H.C. as the more dramatic the engineering change so the opportunity for failings in execution; particularly as these efforts probably did not receive the same sum of scrutiny as the passenger car production product as being of lower production intention and distribution sums, with a slighter time element and budget available to develop, lesser known and greater deviations in environmental field conditions, and not to mention..........not warrantied   

And if after market heads, such as TFS and Edelbock, improve that variation.

      As I have observed too often in the aftermarket products, the engineering has seemed to lack any true 'engineers'; but rather is a "monkey-see-monkey-do" execution; with if the product survives long enough in the market place, perhaps through feed-back from the field (if anyone is listening!    ), it may address the not realized shortcomings of the earlier product with later renditions.  We have been involved in the past with several of the after-market manufactures in reviewing cylinder heads for exactly this concern; as feedback from the field is leading some to infer that there may be an issue.  And although we do have capacities to formulate certain observations and opinions, and my ego might be inflated somewhat for the opportunity, but to think these manufactures are referencing us (or anyone at this level) for this service is not overly confidence inspiring in the subject of their potential engineering capacities, particularly as presented in several instances where as I stated previously, sometimes things just get moved around..........some, with what appears no real concern for the consequences of what might seem an obvious blunder.   

     But believe me, just the fact that the casting material is aluminum, is a salvation in many instances!   

     Scott.

[WConley]

Frank -

Assuming enough coolant flow, and consistent water jacketing (especially around the exhaust valves), the head temperature should be fairly consistent front-to-back.

What many folks don't realize is that water stays at the same temperature as it is boiling.  That temperature depends upon the pressure in the system.  At ambient, it's 212 F.  At 15 psi, it's 257 F.  When you're pumping heat into water and it starts to boil, the temperature will stay at that constant limit.  (Once the liquid water finishes boiling and it's all steam, temperature can now go up from there.  That's called superheated steam.)  Cooling jackets are designed to avoid any steam, so it should be all liquid up there.  That means maximum temperature is set by the water boiling point everywhere in the head.

Here's a good explanation of what the temperature looks like during phase change (boiling):

https://sites.google.com/site/hoyathermochemistry/simple-heat-exchange

Chart from this article:

[Gaugster]

Interesting question. If I really had to know with no limits on time and resources, I would document the head temperature from a cold start up to operating temperature just prior to the thermostat opening. This would require no air movement around the engine. Using a thermal imaging camera or multiple thermocouple sense wires placed strategically. My theory being that whatever section of the engine warmed up the fastest would tend to run the hottest during a temperature surge due to high engine load. At some point the metal and coolant will reach an equilibrium and just lull above and below the thermostat temperature rating. Or at a higher temp considering the boil/pressure comment above. Or thermal runaway...

[jayb]

Frank, your question ignores the coolant paths from the middle of the block up into the head.  There are five fairly large coolant passages in the middle of the block and heads, all near five of the six center head bolt holes, that allow coolant to flow in the middle, before reaching the end of the block.  To say that the coolant flows from the front of the block, to the back, and then into the head at the back and then out the front of the head, ignores all that other cooling flow.  Certainly that additional flow helps keep the coolant temperature uniform in the head.  I don't think there is a significant variation of coolant temperature, at least not on the FE head design.

[frnkeore]

That is a good point, Jay. I was aware of those transfer holes, my assumption is that they are there to cool the ex valve area but, my main interest is, real world temp reading, under power, to see if there are any areas that temperatures are higher.

You could easily, assume that the highest temp, would be at the front of the head and lowest at the rear but, is it a even increase across the coolant path or are there there areas that read higher.

Now, the front transfer holes, could mitigate possibly, even eliminate, what would normally be a hotter front flow, because the entry water will have the lowest temp but, I'm curious to know if the temp's are equal or if there are areas that have increased temp variations.

I'm not worried about it, as FE's haven't had a history of cracking, like SBC do or a over all history of head gasket issues. Although they will blow if there is coolant lose, I replaced them as a mechanic, usually heater or bypass hose issues.

[pbf777]

I would document the head temperature from a cold start up to operating temperature just prior to the thermostat opening. This would require no air movement around the engine. Using a thermal imaging camera or multiple thermocouple sense wires placed strategically. My theory being that whatever section of the engine warmed up the fastest would tend to run the hottest during a temperature surge due to high engine load. At some point the metal and coolant will reach an equilibrium..........

     Note that an initial temperature gain rate of particular sections of the cool mass, (and remember this is a three dimensional subject) say at idle speed with thermostat limiting coolant circulation may prove interesting, but very doubtful if it would truly relate to the scenario of W.O.T. under load, with an already heat gained mass, now with coolant in circulation.  Just to many variables with the heating and cooling temperature differentials interacting with the constantly changing effects in the relationships. This including positions presented within the mass caused by but not limited to: emanation of heat variations in value including position, along with changing velocities of coolant flow and pressures and how this interacts, this with each subject scenario involved.  And this all constantly changing with throttle angle (load), engine R.P.M.s, even vehicle velocity thru the atmosphere (air speed & pressure including changing temperature differentials across radiator (heat exchanger) , etc., etc.; just not many constants resulting in just to many variables to figure conclusively, so I think often it's just a little bit of a crap-shoot by the O.E.'s    ) but based on previous experiences consisting of much trial and error.   

     Often the secondary coolant pathways along the decks are present to increase the coolant flow thru vertical paths and cooling jacket voids as the casting shape presented is much too complex for uniform coolant exposure, and it presents insufficient motion otherwise in these areas as the major fluid velocity motion is one of a horizontal directional value (in this instance); and though often required due to flow deficiencies for system success it does in essence 'short-circuit' the overall intention in the simplistic fluid directional motion map.   

     Scott.

     

[frnkeore]

     Often the secondary coolant pathways along the decks are present to increase the coolant flow thru vertical paths and cooling jacket voids as the casting shape presented is much too complex for uniform coolant exposure, and it presents insufficient motion otherwise in these areas as the major fluid velocity motion is one of a horizontal directional value (in this instance); and though often required due to flow deficiencies for system success it does in essence 'short-circuit' the overall intention in the simplistic fluid directional motion map.   

     Scott.

Along with this, is the question of fluid dynamics and how the flow path can conform to the irregularities, inside the water jacket. It's like aerodynamics (fluid is just very heavy air), it can only follow a contour, so far, as velocity increases and then there will be flow separation, (cavitation) and turbulence.

I used to sell a SBC water pump and in going to trade shows with it, I was told by some engine builders that the stock type WP couldn't be slowed down far enough for high rpm applications, using the commonly available V belts. I used a smaller impeller in mine. I believe Ford found that to be true, also. I have a lot of Ford drawing and I think they made 3 sizes, of impellers, (C3-B, C9-B, C9-A) the smallest drawing (C9-A) I have is 3.75" dia. But, I don't have the drive ratio that it was used. Does anyone that info, I'm sure it would be what was used for NASCAR engines. The C3-B, is labeled as the Original 427. Both the C3-B and the C9-B have 12 impellers, differing in there shape (8 long 4 short). The C9-A (3.75 dia) has only 6, equal impellers, with a very simple shape.

[Rory428]

Just a thought, and bearing in mind I am far from any sort of engineer, but considering the manufacturers seem to have no consistency in where they installed the sender for the temperature gauge, they must not believe that there is any significant variation of coolant temp throughout the engines cooling area. Although most Ford V8s have the temp sender at the front of the intake manifold, including the FE, the 272-312 Y Block had it at the rear of the drivers side cylinder head, the 351C/351M/400 is at the passenger side  front of the engine block, (no water in the intake, but certainly is in the heads), Chevy V8s typically had the sender located in the middle section of the cylinder heads , on the exhaust side, etc. This would lead me to believe that the OEs considered the coolant temps must be fairly equal through out the engine. Maybe I am way off base, but that is just something that I have observed over the years.

[Falcon67]

I do know of one modifications to the 351C/M/400 line around 1975 (?) I'm just thinking that time they were doing all kinds of oddball things to engines to meet emissions and MPG requirements. 

Note the cooling passage around the exhaust valve in a 1975 351C 2V head that is not found in earlier versions. The last time I looked for a good 351C 2V head, I went through several before finding a single unit without cracks around the exhaust valve and seat area.

[jayb]

Cooling passages around the exhaust valve seat and the spark plug hole are very important considerations when designing a water jacket for a cylinder head.  I'm rather surprised that Ford didn't have coolant around the exhaust valve seat in the early 351C 2V head, the issues with lack of cooling around the exhaust seat have been well known for many years...

[FrozenMerc]

I can't speak to FE's, but I have done this exercise on smaller engines (single, V-Twin, and Inline Twin two and four strokes) in the past.  I would drill and tap dozens of holes into the water jackets around the cylinder and throughout the heads and install thermocouples.  It wasn't unusual to have 12 to 16 thermocouples mounted in the cylinder, and another 8 to 12 in the head on these engines.  This was almost always done on prototype engines, or new designs to make sure there wasn't any problems during initial run-in and fuel mapping.  Generally speaking, there wouldn't be more than a few degrees difference between the thermocouples, once the engine was up to temp.  Warm up would show a bit of difference, especially with the thermostat closed. 

The one engine that would show a large temperature difference would be the direct injected two strokes.  The fuel was sprayed through a window in the piston towards the transfer ports.  The spray pattern would hit the opposite side and keep that cylinder wall considerably cooler.   Took a looonnnng time to figure out how to properly cool the piston on that design to keep it from splitting along the window and sticking in the bore. 

[Falcon67]

Not sure when Ford got around to addressing the problem on the 351C 2V type heads.  The 70-71 heads have the better exhaust port, then this 75 thing.  That's going by casing numbers BTW.  I think I magged like 8 heads before I found a good replacement.  Ported, the set ran around 254 cfm intake / 200 exhaust at around .550.  Conversely, I have not found the same exhaust issues with any of the 351C 4V heads I've owned and magged.  I wonder if the problems only showed up post 1974 production.  Looks like Cat converters showed up in 1975 - that would have really heated up the exhaust head temps I'll bet.  The 1993 F-350 460 is also known for overheating the exhaust manifolds and either cracking the manifolds or causing bolt problems.  No head issues, just the bolted on parts.

[WConley]

... The 1993 F-350 460 is also known for overheating the exhaust manifolds and either cracking the manifolds or causing bolt problems.  No head issues, just the bolted on parts.

That's why they specified cast stainless exhaust manifolds on those 7.5L truck engines.  I remember dynoing those at Ford and oh man you could cook some nice marshmallows just holding them near those glowing things.  It had something to do with the chamber design and cam/ ignition timing needed to meet emissions.  We had problems with 7.5L E-350 Ambulance fires for awhile    Not a good look to see a whole row of burnt out ambulances on the infield of the Dearborn Proving Grounds.

[pbf777]

Conversely, I have not found the same exhaust issues with any of the 351C 4V heads I've owned and magged. 

    I would agree with this with the exception of the later open chamber, small valve, 4v head, identified as the 'AA' casting; as we have found these to often exhibit cracks between the intake and exhaust ports seat thru seat.   

    Scott.