Engine melt down

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Not surprised. The gap between a sleeve and the actual cylinder block CAN Not transfer the heat to the water jacket the same as the original cylinder block can. Obviously there is a lot that you don't know !!! Its not my problem.
 
I think I agree with Purdy on this one. Every "juncture" to the passage of heat presents additional resistance beyond the resistance of the two bodies. It's called the "skin effect" in thermodynamics and has to be accounted for in the passage of heat between discrete solids.

It can be looked upon as each juncture has "air" between the solid bodies. Air, even a molecule thick offers greater resistance to heat flow.

Rebuilders can do a lot to minimize this resistance between a sleeve and the parent cylinder block - like using various fillers and adhesives designed to improve the conductance of heat. Some don't use these and rely on the force fit of a sleeve to maintain the contact between surfaces. To the detriment of heat flow IMHO.

Joe K
 
In response to the post on the seized piston on #4 cylinder, I also have seen ths type of failure and blamed it on insufficient clearance when the engine experiences temperatures at or near the extreme upper operating temperature limit due to running hot and boiling in the radiator. I would like to refer to MikeK's post below. Please keep in mind MikeK is correct about the expansion of the bore, but most individuals overlook the fact that aluminum has approximately twice the thermal expansion rate of cast iron, thus a piston in a bore will reduce the clearance if the block and piston are elevated to the same temparature. I am not saying the piston and cylinder wall are at the same temperature as each has separate and distinct methods of heat transfer such as conduction to the water and radiation on the block and conduction to the oil and to the air/fuel mixture with the piston but with this fact of different rates of thermal expansion in mind, the piston can contact the cylinder wall due to a minimal amount of set up clearance combined with elevated operating temperatures. I always recommend the upper maximum for piston to cylinder clearance in the Model A engines when the machine shop hones the block for new pistons.

My opinion only, but backed by physics.


From Mikek's post: There's always a lot of talk about #4 cylinder running hot, but one point is overlooked: If the cylinder (block) gets hot, the bore actually increases in size. For the piston to seize the piston itself must get proportionally hotter than normal. For this reason I believe it is not the direct result of the block around #4 running hotter.
 
Bob,

What about timing retarded on number 4? The number 4 distributor cam lobe could be retarded compared to the others. I have seen pistons tie up due to retarded timing.

Will miss you at Fort Bragg...

A's Always
Dave
 
Chuck Sea/Tac said:
Tbird, is putting a clean piston w/o rings in a clean hole and then checking with a feeler gauge acceptable procedure?
Click to expand...
I am not Tbird, but I note on page 204 of the service bulletins, Ford said in 1928:-
Quote:"FITTING PISTONS AND RINGS.Model A pistons are fitted in cylinders loose on .002 inch and tight on .004 inch.
When fitting pistons, use a long feeler (thickness gauge) that extends the full length of the piston. Insert the feeler between piston and cylinder wall on the opposite side of the piston from the slot in the skirt.
When properly fitted a .002 inch feeler can be inserted between piston and cylinder and the piston moved up and down in the cylinder bore with a very slight drag. When the same check is made with a .004 inch feeler, the piston should fit tightly in the bore" Unquote
My tests show this will give an accurate .003 inch clearance., ratifying what Chuck Sea/Tac asks about the method. But the pistons were different and slotted in 1928, so the .003 may not apply now.
I just set my new Snyders pistons in an 0.080 over bore to .0035 clearance (following T/Birds advice), using dial-type bore gauge and micrometer and checked it with .003 loose and .004 tight feelers to get the same .0035 answer.
All new pistons were exactly the same size but the weights varied quite a lot and the gudgeons were far heavier than originals. Everything was balanced to within 0.5 grams and motor is running nicely at 500 miles, but I am still taking it easy and watching temps. and head nut torque in view of what is being reported here, plus other members engines I have examined internally. Bores were honed to individual pistons to get exactly 0.0035, Since all pistons were on size for +.080 from memory, clearances were formed by honing the bores .0035 inches over the +80 thou. dimension
I have an EGT gauge fitted next to No 3 Ex., plus a water temp gauge.
 
very carefully fitted, SAJ, you should be fine.

we use the inside mic to check as we are honing, then the feeler gauge method after all is cleaned up as a double check. Be sure to get the feeler down below the ring lands.

Of course checking ring gap is important, too, else you can score cyls or lockup also from insufficient gap. I have posted the specs that we use here before
.022 top
.016-18 second

we have worked on more than one engine with insufficient gap
 
When checking clearance with a feeler gauge, remember that the piston skirt is tapered and is largest at the bottom of the skirt, 90 degrees from the wrist pin. Ron W
 
Number 4 cylinder is the last one in line for the air that has already taken heat from the other 3 cylinders. If you look at the A block you can see the bottom of the cylinders are air cooled. Most engines in cars have water jackets to the bottom of the cylinders.
With out water to cool the bottom this helps to make it run hotter. Yes 3 and 4 score first in most engines if every bore has the same clearance.

Pistons have are not pure aluminum. So different brands have different expansion rates. Maybe around 1 1/2 times the rate of cast. But I'm not sure of the rate. But it is more than cast. Plus the piston will run hotter than the cylinder wall, it has to get rid of its heat to the cylinder wall and oil in the engine.

Bottom line I always tell anyone that I did a engine for. Do not take it out on a 95 degree day when it is not broken in, and run it 45 for a long time.

Make a few short trips that bring it up to operating temp. Until it frees up and you have some miles on it.
 
Tom -

Thank you sir as I learned quite a bit from your response and from many other contributors.

I am fortunate that I have a rebuild of the Coupes original engine put together by a local Nor Cal legend - Cecil Kissinger. :) As the engine was built in 1978, I know this Oklahoma native used and had access only to American made products (when at all possible).

We are fortunate to have a pool of experienced folk that can assist in keeping our Fords on the road.

Be well -


SHEC - :cool:
 
When my engine failed a year ago, the month was November and the ambient temps were in the mid 50's and it was raining. The water temp was well below 160. The car had been running fine for about an hour when the engine abruptly failed. The two photos show the damage that was done to the pistons. The one severely melted is the #4. The other three also showed signs of overheat and some melting. The engine had a .060 over bore (no sleeves). It was later bored out to .080 when the Silv-O-lite pistons were installed. The engine had new babbitt mains and rods, the valves and seats were stainless, and a 5.5 Snyder head was installed. A Jim Brieley cam was installed. Valve clearance had been set at 12 &14. Carburetion and ignition was stock Henry, with the jets in the Zenith flow tested and re-sized within the specified window. Timing accurately set, points set at .020 and the spark handle down a nominal half way. GAV was cracked open about 3/4 of a turn. I was climbing a slight grade at about 50 mph in overdrive (23% Ryan). the engine was definitely not lugging.

The resultant damage was confined to the pistons, other than aluminum debris scattered around and the cylinder walls scored, there was no other engine damage. The engine builder said he had set the piston clearance at .004 -.005.

I am pretty sure I know how to drive a Model A. I am still convinced it was all about piston quality.

Tom Endy
 

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Like WoW!!!
crap pistons for sure IMO

and I would surely think you do know how to drive an A; it amazes me that anyone would challenge that......
 
Engines that have been sleeved back to standard size will always run hotter .

If the above comment were true then all of our Model A engine and other engines wouldn't require a thermostat to get them up to temperature. Also we would of heard many complaints of people with sleeved engines complaining of overheating.

Yes there is a right and wrong way to install a cylinder sleeve but to say that it doesn't transfer heat just doesn't make any sense.
 

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For the Guy that said I flap my lips, that his Post disappeared on this post.

This is what he said, not what you thought he said, and did say, as you got it wrong!

Sleeved cylinders can't transfer the heat to the water jacket the same because the sleeve isn't actually part of the original cylinder block."END QUOTE"

This is what he said, and it is still B.S.

Sleeves have no ill heating effects on T's, A's, B's ect. what so ever, so why even bring it up as a Question for someone who doesn't know, and if it were a problem, every engine builder would have known about it 100 years ago.

Herm.
 
About sleeves- many large industrial engines are manufactured new with sleeves. Some 'wet', some 'dry'. I guess they all overheat. :rolleyes:
 
i see where it is recomended here that clearance for pistons be set at least .0035 up to .0045. At what point does piston slap enter the picture?Thanks
 
Thermal conductance

It is true that the transfer of heat from one piece of metal to another is not as efficient as a solid piece of metal. How close it is to solid metal depends on the interface between the two pieces of metal. An example of this are the heat sinks that are used on computer chips. To get better heat transfer they use a thermal paste between the CPU chip and the heat sink. Without the thermal paste the heat transfer would not as good and the CPU would fry. In that case the heat sink and the CPU chip are just clamped together. In the case of a cylinder sleeve they are held together with an interference fit. The tighter the fit the better the heat transfer. The heat transfer from the sleeve to the block will always be less efficient then an un-sleeved block.

The question here is how less efficient is the heat transfer in a sleeved block. I do not know for sure. It could be very poor for a sleeve that is not very tight in the block. It could also be almost the same as an un-sleeved block if the sleeve is real tight in the block.

It may be true that a sleeved block is going to run warmer than an un-sleeved block. But the amount may be so small that it is not noticeable.


Bob
 
The pictures seem to show the impression of piece of ring on top of the piston. That suggests that the ring was expanded too much and broke the top of the piston. It may have been a combination of things that resulted in the failure. I don't believe a sleeve was any part of it. When we build an engine, we try to use good parts and fit everything to specs but we are only human after all. I once used a compression ring that I knew had a slight kink in it. It didn't seem bad enough to bother but it did and I paid the price by having to tear the engine down later to fix things. Ron W
 
not at those numbers.

But if the pistons are run tight, and overheat, and swell, they shrink when they cool, and then they will slap like crazy....and when you yank them out for replacement they are scored all up as well as the cyl walls.
 
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