Need some pistons Knurled

[Kurt in NJ]

It is a way to increase the diameter when they are worn, a knurl is formed on the pistons, it is then filed some until the pistons fit the bore, usually done by feel,

 

[McMimmcs]

It is a way to increase the diameter when they are worn, a knurl is formed on the pistons, it is then filed some until the pistons fit the bore, usually done by feel,

Thank you. Would the process be cheaper than buying new pistons ?

 

[Randall]

I can knurled pistons

 

[Synchro909]

Thank you. Would the process be cheaper than buying new pistons ?

The problem with buying new pistons is that they come only in increments of 0.020". If the bore is worn to say, 0.015" over, it will be tapered as well as over sized. The usual treatment is to bring the cylinder back to round and parallel as best it can be without a full rebore and knurl the pistons. The alternative is to rebore, then put in new pistons. Knurling is cheaper than that an is enough to keep the engine going for a while.
Personally, I don't go that route because I don't think the saving is worth the time and effort required for a little more life.

 

[Terry Burtz Calif]

Why do they knurl pistons ? Wayne

In the 1950's and 1960's, used car dealers or individuals who wanted to sell a worn-out car would have the engine rebuilt where the only new parts were a set of new gaskets and some paint.

In my area, "Automotive Engineering" was the place to go, and their radio jingo was "Make your car run like new".

Instead of new parts, knurling was used on almost every wearing surface to reduce clearances.

If I recall, the cost of a V-8 "rebuild" was $69.00.

Without the engine in the car, the engine compartment could be steam cleaned to look like new, and the newly painted engine looked great to the potential customer.

After purchase and 1000 miles, the engine and engine compartment were worse than before the rebuild.

 

[Fordestes]

Why do they knurl pistons ? Wayne

Knurlizing pistons was an accepted practice for sizing new and used pistons , knurling can be used to tighten piston skirt to cylinder wall clearance making the piston more stable and by allowing more cylinder wall to piston ring contact area for better oil control, it also helps reduce scuffing due to greater load carrying capacities, just to name a few .

 

[SAJ]

I have a piston expander from 1930's called a Koetheriser. It expands by squeezing the skirt into a more cam-shaped form and then stress relieving the piston by shot blasting inside with small steel shot, so it holds the new closer tolerance shape at the skirt.
It has done many thousands of engines with great success over 80 yars and I still use it now. Most recently on a 2.5 litre Riley engine and a 34 V8.
Apologies that it is not much help to the original poster, since I am too far away. But somewhat relevant to the topic and maybe interesting to a few
SAJ in NZ