Temp variance between cylinders

[tbirdtbird]

Several of us in the past have stated that cyls 3&4 run hotter than 1&2.

Today I did startup on a clients A motor that we had to re-work extensively because the prev. shop had set the piston-wall clearance too tight ( We see this all the time). Piston 3 got real hot, then shrunk, giving him a knock. We had gone thru all the easy stuff before commiting to pulling the head and dropping the pan, which we do over a pit. While in there he wanted to change out for a Bill Stipe B profile with .330 lift

The piston is badly scored and I will post a pic later. Fortunately the walls were not bad at all, the bores needed to be honed anyway. He had done little driving once the knock appeared.

All cyls were honed in our shop to 3.955 which is 080 over. (these bores were .001-.002 too small). Pistons installed were custom 283 style (short skirt) from Pete's Auto Machine in Albuquerque NM. These custom pistons allow you to use the original A rods. (an extra 1/8" of meat has been added to the top of the basic 283 piston. The machining of the pistons is such that the clearance is built in; i.e. they are machined .0035 under the 3.955.

The startup and initial cam break in went even better than expected. After full warmup, I used my temp gun on the cyls from the driver's side of the engine. Please know that the motor spins freely whether cold or hot.

Here are the readings:

1- 210 degrees
2- 210 degrees
3- 240 degrees
4- 240 degrees.

This is why you cannot set piston to wall clearance to modern car standards (usually .0015); which happens all too often.

You must use .003-.004; else bad things will happen. You be the judge.

[Kurt in NJ]

Are these temps from the cooling jacket, or the area under the cooling jacket ---the temps seem high to me, i have never measured the temp, but the area below the water jacket runs much cooler than that on my car---it doesn't burn quick enough to be that hot when i touch there, and my water jacket doesn't run that hot either

[tbirdtbird]

" i have never measured the temp"

try it

[MikeK]

I've always been curious about the water deflector in the block that directs cooled radiator return water forward. 3&4 see less water circulation. Perhaps not one of the better design ideas. That deflector in the block changed in size as the engine evolved.

CORRECTION: Oops! The deflector faces rearward. Thanks, Tom W. for catching my 'senior moment'.

[Bob Bidonde]

The coolant system in the Model A & B Fords is a poor design, but marginally good enough. Overheating, foaming and head gasket burnouts between Cylinders 3 & 4 account for more complaints from Model A & B drivers than anything else perhaps except for the cars brakes.


Coolant tends to bypass cylinders 3 & 4 because the flow tends to take a straight path from the water inlet on the side of the block between Cylinders 2 & 3 and the water pump.


The temperatures for Cylinders 3 & 4 you are experiencing are not unusual, and I would expect some temperature reduction (friction decrease) after the engine has some miles on it.


Many years ago a fellow put a pipe fitting into the water jacket behind Cylinder 4 in an attempt to redistribute the coolant flow. This requires some experimentation to restrict the flow into the side of the block, but it should make an improvement.
Fundamentally, the water pump is in the wrong part of the coolant system. The pump's coolant intake should come from the bottom of the radiator so there is always a positive pressure head on the pump's intake. Output of the pump should be directed to the rear of the cylinder block instead of the side of the block. In this manner, mass flow would positively pass Cylinders 4, 3, 2 & 1, making 1 & 2 the hotter running cylinders. Cylinders 1 & 2 benefit from cooling airflow, so these cylinders can accommodate the higher temperature coolant they would see from Cylinders 3 & 4.


The high temperatures of Cylinders of 3 & 4 is one of the reasons I use synthetic oil.

[George Miller]

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Originally Posted by tbirdtbird

Several of us in the past have stated that cyls 3&4 run hotter than 1&2.

Today I did startup on a clients A motor that we had to re-work extensively because the prev. shop had set the piston-wall clearance too tight ( We see this all the time). Piston 3 got real hot, then shrunk, giving him a knock. We had gone thru all the easy stuff before commiting to pulling the head and dropping the pan, which we do over a pit. While in there he wanted to change out for a Bill Stipe B profile with .330 lift

The piston is badly scored and I will post a pic later. Fortunately the walls were not bad at all, the bores needed to be honed anyway. He had done little driving once the knock appeared.

All cyls were honed in our shop to 3.955 which is 080 over. (these bores were .001-.002 too small). Pistons installed were custom 283 style (short skirt) from Pete's Auto Machine in Albuquerque NM. These custom pistons allow you to use the original A rods. (an extra 1/8" of meat has been added to the top of the basic 283 piston. The machining of the pistons is such that the clearance is built in; i.e. they are machined .0035 under the 3.955.

The startup and initial cam break in went even better than expected. After full warmup, I used my temp gun on the cyls from the driver's side of the engine. Please know that the motor spins freely whether cold or hot.

Here are the readings:

1- 210 degrees
2- 210 degrees
3- 240 degrees
4- 240 degrees.

This is why you cannot set piston to wall clearance to modern car standards (usually .0015); which happens all too often.

You must use .003-.004; else bad things will happen. You be the judge.

I just put a new Burlington crank and new rods with 283 pistons in my 28 Sports coupe. It really did not need them , but I want a new crank before they were gone.

I checked the cylinder temps. Which were about the same as above. I also seen piston scoring on 3,4 many times. Most of the ones were on 3.

[Tom Wesenberg]

That's what happened to my temporary engine in my 28. I installed it without removing the head and I was unaware of the rust buildup near the last two cylinders. The engine had a bad pinging with the slightest throttle with the spark lever set half way down. This engine always had a noise that I suspected was a loose piston skit, and by shorting plugs it seems to be #3. Once I got all the rust flakes out of the block the pinging went away, but I'm sure the cylinder hot spot due to rust buildup had caused the piston skirt to collapse, so I'll just have to listen to it until I rebuild the engine or knurl the skirt. If I could find my piston skirt expanders I'd drop the pan and install those.

[Benson]

Originally Posted by MikeK

I've always been curious about the water deflector in the block that directs cooled radiator return water forward. 3&4 see less water circulation. Perhaps not one of the better design ideas. That deflector in the block changed in size as the engine evolved.

CORRECTION: Oops! The deflector faces rearward. Thanks, Tom W. for catching my 'senior moment'.

I hesitate posting anything here anymore due to some snotty remarks about my postings in the past of warnings that I have discovered over the last 52 years.

This is not directed at MikeK ...

Anyway here is an article on Marco's website:


http://www.abarnyard.com/workshop/inlet-1.htm

[MikeK]

Originally Posted by Benson

I hesitate posting anything here anymore due a number of snotty remarks about my postings in the past of warnings that I have discovered over the last 52 years. This is not directed at MikeK ...

??? Why quote and use my post as an example? I must have missed something. Yes, I make mistakes and will correct them. Whether I receive a polite PM questioning a statement or am blasted in a follow-up post starting with ..'Hey, Dumbass..' doesn't matter or reduce me to lurking. When I'm wrong, I'm wrong. Life goes on.

[James Rogers]

If all this is true, what is up with my Model T? I have 2 and have never run a water pump on either and never will. The cooling system is virtually the same on the T as it is on the A but I never experience overheating in it even in Utah in July or South Dakota same month or TN in August on a asphalt parking lot idling. I have seen ambient temps as high as 102 and no overheating even on a long pull.

[George Miller]

I do not think we were talking about over heating over all. We were saying the back two cylinders run hotter than the front two. So if the pistons are to tight, the back ones are the first to score.

[Tom Wesenberg]

I took the temps on several places on my 28 engine last summer. I can't find the sheet where I wrote them down, but plan to redo the checks as soon as I get my car out of winter hibernation. We just had 2 more inches of snow last night so it won't be anytime soon. Now that I have all the rust flakes removed (I hope ) it should provide some good readings.

[Benson]

Mike,

I was not questioning your posting in anyway.

Sorry for the way this came across ...

It was not meant that way at all!!!

I only highlighted your post to refer to Marco's info in support of what you said about the changes made by Ford in 1929, as Marco's info has an illustration for those not familiar with what we are talking about.

As to the statement about snotty statements ... I was venting about past experiences and should not have included it here!!

[George D]

Installed a rebuilt engine about 2 years ago and ran into trouble with #3 getting tight during break in. Took temputure of each cylinder while running and found 3&4 to be about 20 degrees hotter, figured it would right it's self after awhile . 2500 miles later engine runs perfect never had any overheating troubel of any kind but 3&4 still run hotter then 1&2, nature of the beast. After reading this tread I got wondering, if a head gasket that had slightly smaller water passages near front of block would act to balance this out a little. More water would be directed to rear of block, sounds like a nice science project.

[Mitch//pa]

maybe a contributing factor is because 3&4 are further away from the fans air flow

[Will N]

Originally Posted by James Rogers

If all this is true, what is up with my Model T? I have 2 and have never run a water pump on either and never will. The cooling system is virtually the same on the T as it is on the A but I never experience overheating in it even in Utah in July or South Dakota same month or TN in August on a asphalt parking lot idling. I have seen ambient temps as high as 102 and no overheating even on a long pull.

The Model T is only 20 HP, and HP=Heat. The T doesn't have to get rid of as much heat as the A has to. The natural circulation of the thermosyphon is not impeded by or overidden by the water pump as in the A, which as Bob B mentioned, forces the water to take the path of least resistance from the inlet to the outlet, bypassing the rear of the block.

[James Rogers]

Originally Posted by Will N

The Model T is only 20 HP, and HP=Heat. The T doesn't have to get rid of as much heat as the A has to. The natural circulation of the thermosyphon is not impeded by or overidden by the water pump as in the A, which as Bob B mentioned, forces the water to take the path of least resistance from the inlet to the outlet, bypassing the rear of the block.

I don't really believe that. I have a 94 Ranger with the Mazda 2300 engine that had a water pump with a detached impeller that would never even get up to operating temp till I replaced the pump. I couldn't figure out why it wouldn't work the heater till I found out the water was not circulating through the heater core. The previous owner had replaced the radiator and heater core with new and never found the problem. As with any motor with cylinders in line, the #4 cylinder had gotten hot simply because the back cylinder on any motor will be hotter but without circulation of the pump, it burnt an exhaust valve. Replaced the head with a rebuilt and replaced the pump and 12000 miles later it is working like new. BTW, this motor is 90 HP so, according to your estimation, it should have burnt up in a very few miles.

[James Rogers]

Originally Posted by George Miller

I do not think we were talking about over heating over all. We were saying the back two cylinders run hotter than the front two. So if the pistons are to tight, the back ones are the first to score.

I believe that, any engine with one cylinder behind another will always have the rearward cylinders hotter by comparison. This is a matter of physics. The problem comes in when this causes overheating and engine damage. I do agree, this difference in heat can cause problems if a builder holds his clearances too close or excessively tight. Common sense should come into the equation at some point and tolerances should be held to the loose side by 1/4 to 1/2 a thou.