Piston clearance for 1917 Ford

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Model T Ford Forum: Forum 2012: Piston clearance for 1917 Ford
Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Diederich on Wednesday, October 03, 2012 - 11:02 am:

How much clearance should the pistons have when in the cyl bore? I have about a sixteenth of movement both forward , backward and side to side. This seems to be too much to my way of thinking. I only found this when I removed the head to clean out the carbon.
Thanks Bob D


Top of pagePrevious messageNext messageBottom of page Link to this message  By Scott Conger on Wednesday, October 03, 2012 - 12:01 pm:

are you saying that there is 0.0625" difference between the diameter of the piston and the diameter of the bore (1/16 inch)?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jerry Ostbye on Wednesday, October 03, 2012 - 12:42 pm:

At the top he is.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Scott Conger on Wednesday, October 03, 2012 - 01:21 pm:

If that's the case, then the answer is "technically, yes, that's too much".

Then you ought to consider: does it pump/burn oil, does it knock, run poorly/overheat?

I have a '19 roadster that I recently replaced a head gasket on (head had been installed with a heavily rusted surface and was leaking compression). I too found a lot of clearance (but honestly didn't measure like you have. This engine is loose, gives multiple free starts, doesn't pump oil, runs beautifully and tours consistently and reliably. It's an original engine with Cast Iron pistons.

I could correct the excessive wear at considerable cost and time, and would not necessarily have a car that is any more reliable. No doubt it would be peppier, but at what price?

I firmly believe that a lot of "T" engines get rebuilt long before their serviceable life is actually exceeded.

So the bottom line is, evaluate how it is sounding and performing, and probably start saving your nickels for the inevitable (but not necessarily imminent repair).


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ted Dumas on Wednesday, October 03, 2012 - 01:25 pm:

Are the pistons cast iron or aluminum? Have you accurately measured the slop? Appearances can be deceiving. Maybe you may need attach a dial indicator to the piston and do some measuring.

Let's ask the bigger questions: How did it run?, Does it knock?, How much compression do you have?, What is the difference between a wet and dry compression test?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Robert Scott Owens on Wednesday, October 03, 2012 - 02:17 pm:

Hey Bob, How many threads are you going to start on the same problem? The piston will move back and forth and side to side on the top. It is pivoting on the wrist pin. Most pistons are cam ground as the top of the piston get hotter than the skirt. So the way to tell is to remove the piston and measure everything. If you have the head off you have most of the work done so pop one out and check it. You will need an outside and inside mike. Its easy to and then you will know. Scott


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