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Cylinder #4 Running Hot Cylinder and exhaust port #4 run hotter than the other cylinders and exhaust ports. I believe this is due to reduced cooling water flow in this area.
The original Model A cylinder block castings (A-6015) have a large elongated hole between cylinders 2 and 3 that are open to the water jacket. This hole is the result of a core print that was used to support the water jacket core during the pouring of the casting. When I look at the Parts Index on the MAFFI site, I see that the head (A-6050) and cylinder head gasket (A-6051) both changed during production to have an A suffix. I'm thinking that early heads (A-6050 without a suffix) did not have the large elongated hole between cylinders 2 and 3. I'm also thinking that later heads (A-6050-A) had the large elongated hole. When the large elongated hole is present in the head and cylinder head gasket, cool water entering the cylinder block can take a shortcut through the elongated hole, and the flow around cylinder and exhaust port #4 will be reduced. My thoughts are that cylinder and exhaust port #4 will run cooler if the large elongated hole is not a through passage. Perhaps the change was made to prevent water pump cavitation without considering what would happen to water flow around cylinder and exhaust port #4. It would be interesting to see the difference in temperature if the same engine were run with heads with and without the elongated hole and have the temperature measured with an infrared thermometer. Please comment, and if anyone has access to the archives, that would be additional information. |
Re: Cylinder #4 Running Hot Terry,
Archives are closed till God Knows When! Pluck |
Re: Cylinder #4 Running Hot I have tried to duplicate #4 being hotter than the other cylinders--- let it idle for a hour, drove over 55 for hour, then let it idle again -- #2 got 2 degrees warmer than4-- some of the temps swapped readings, all within less than 5 degrees
I did do a real good cleaning of the block including reaming the rust out of the little hole at the back of the block and head---35 years ago, always antifreeze, most times the gav is near closed, full advance for timing--- I took readings along the sides of the block at waterjacket, below water jacket along length of head, inlet, outlet Perhaps it is because I have old style in hose thermostat I also checked shock temperature-- hit every bump I could find, they only gained 5 degrees |
Re: Cylinder #4 Running Hot Quote:
I agree with this. I have never seen evidence of this either. A Model-A engine just does not run that hot under normal circumstances. Additionally, if you think about the entire scenario, the hottest part of the entire cylinder is the chamber roof of the cylinder head. Heat also rises. The #4 port should not be running any hotter unless the exhaust is restricted somewhere which is not allowing for the spent exhaust gasses to evacuate. That is why I don't subscribe to it being an issue with the cylinder block or piston clearance. |
Re: Cylinder #4 Running Hot I agree with Brent. As long as the water jacket back behind #4 is cleared of rust and trash, so that the coolant flows through there, it's not significantly hotter than the other cylinders.
It would be interesting to see if there are any memos or other documentation in the Ford Archives discussing why the elongated hole was added. Cavitation is a real possibility. |
Re: Cylinder #4 Running Hot I remember there was an article in the Restorer many years ago (1970s?) where a detailed temperature test was done on a Model A engine. It was titled "Nothing Happens in No. 1 and 2". As part of the test, the author bored and tapped a hole in the back of the block and installed a copper pipe routed to the inlet casting on the side of the engine. This would bring cooler water from the radiator to the back of the engine. Sure enough, this stagnate flow area was eliminated with corresponding cooler temperatures. The only problem was it looked crappy, ruining the look of an original engine! It is one of those improvements that isn't necessary for the present owner. The car is going to last longer than we do with good maintenance and driving habits. Ed
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Re: Cylinder #4 Running Hot Quote:
Hi Ed, unfortunately there are many times where the editors accepted an article for print and the readership then accepts it as 'gospel' since it was printed in the national club magazine. In theory, if the article was factual, it would seem the better location to install a pipe would either be into the side, -or rear of the cylinder head, ...and not the block. Let me also add something for those to think about. A Model-T engine has no water pump to circulate/move the water, has smaller water jacket areas, and has a smaller cooling fan. With all of these shortcomings, a Model-T engine is never said to have cooling issues on #4 cylinder. So why is it that a Model-A engine supposedly has #4 cooling issues yet a T engine does not? Could it be that someone started that 'He said/She said" theory about #4 overheating, and because it seemed believable to the unknowing, others jumped onto the bandwagon until enough folks hears it and repeated it until it is now considered fact? Lord knows there are many other such similar myths such as Ford using up parts inventory until depleted, or used shipping crates for floorboards. I honestly believe the #4 overheating myth is similar to those other myths. |
Re: Cylinder #4 Running Hot The Model "A" engine makes twice the power of the Model "T" engine, so it runs hotter.
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Re: Cylinder #4 Running Hot Cylinder 4 does not get the benefit of pumped coolant flow, so it runs hotter. What compensates for the lack of pumped coolant flow about Cylinder 4 is the 3 coolant jackets that surround it. These jackets radiate enough heat from the coolant to keep Cylinder 4 at a successful operating temperature. However, the coolant jacket behind Cylinder 4 has a tendency to collect debris which degrades the radiation from the rear coolant jacket of the engine.
There is no coolant flow between the cylinders in the Model "A" engine, so the cylinders have hot spots where they connect. At Cylinders 3 & 4, the connecting cylinder walls run hot enough to eventually burnout the head gasket. |
Re: Cylinder #4 Running Hot I've never thought #4 ran any hotter, but have never measured it. I do run electric 'pusher' water pumps, this may help. I've thought of doing similar to what Ed in Maine talked about, only using an internal water manifold like Chrysler products used, aiming water at the area between the ports, where cracks often appear. I would only do this on a race engine, too much useless trouble for street use.
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Re: Cylinder #4 Running Hot Over the years, I have been asked to repair damaged engines that have had inadequate cylinder to piston clearance. I have noticed that the damage is almost always at number 4 or 3 cylinders. The worst area of damage is adjoining the Siamese area of the block to either the cylinder or piston.
So based on these observations, I believe the rear two cylinders run a bit warmer. Whether block, head or coolant passage design, debris around the rear of #4, something causes the more frequent failures at the rear two cylinders. In building engines used severely, under high sustained loads, I actually hone the rear two cylinders a couple tenths larger than the front two and as a result, do not have issues. Good Day! |
Re: Cylinder #4 Running Hot We have built FLATHEAD model B race engines that make over 200 hp, and the cylinders run within 3 degrees of each other. The water jacket needs to be clean like it was from the factory, not plugged with 40 or more years of plain water coolant abuse.
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Re: Cylinder #4 Running Hot I have never seen a piece of paper refuse to take ink! This may explain everything???
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Re: Cylinder #4 Running Hot If the info on #3 and 4 running hotter is just a myth, why did Ford make changes to the block at the inlet?
I believe that a CLEAN water jacket will keep things running just fine and to get it clean, we use the Liquid Intelligence product made for the purpose. I have posted about it on here before. |
Re: Cylinder #4 Running Hot Quote:
Terry, Just how much temp difference are you seeing? |
Re: Cylinder #4 Running Hot Was the deflector at the water inlet of the Model A block originally there? Or was it added later in production?
See picture in post #17 in: https://www.fordbarn.com/forum/showt...hlight=cutaway |
Re: Cylinder #4 Running Hot The cooling system of the A is pump assisted thermosyphen, thermosyphen action starts working when coolant is over 180--- watch a pot of water before it boils, the water gets active and flow can be seen a little before boiling, perhaps it not that #4 is too hot, but other areas are too cold
I found with my car that the temperature was just a few degrees different, and the hotter/cooler places moved some depending on idling,driving slow-fast, heat soak I have a 160 degree thermostat, but it is old in hose bi- metal type with butterfly valve |
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