fordson f bore size and pistion clearances.

[doug12]

I am in the process of restoring a early 20s fordson f. I am disassembling the engine and got the pistons removed. I measured the bore at 4.012. What should the the bore be? What is the maximun piston/ bore clearance that will allow for good compression? My feelings is I am going to have to have the engine bored and sleeved.

Any infomation is much appreciated.
 

[cdmn]

The first 10 years of Fordson, the Std bore was 4.000 inches.

Beginning in about 1929, the Fordson had a slightly larger bore, 4.125.

In 1938 it got a higher compression head. The result was that the bearings were over-stressed and the engine suffered reliability.

So the conclusion is, the stock Fordson is barely adequate.

By 1945, they were getting 27 hp out of it.

To go non-stock takes money: hardened, counterbalanced crank, bearing inserts, pressurized lubrication, stronger rods.

People are doing it with Model T or Model A engines.
 

[cdmn]

It seems like if you can get the taper removed, a .010 oversized piston and rings would do it.
If necessary, a rebore of .020 oversize would clean it up.
Piston clearance of 0.005 on the diameter is what they recommend for Model T's. It may depend on the metal in the piston. Rings are fitted with a gap at the ends, to allow for thermal expansion.

Should be no need to resleeve.

In most engineering, the hole is basic. Clearance is built into the piston.

Modern piston rings would be much improved over the old style iron rings. For parade purposes, you may not need to do anything.
 

[Butch Howe]

Like I said on the Smokstak. Put cast rings in it and run it.