To Hone or Not to Hone

[Ron LaDow]

Piston skirt-to-cyl. max. wear diameter is around 0,02mm (.008") w/cast iron cyl;

Dick, we used to set Forged-Tru hot-rod pistons at .008", cold, on water-cooled engines, but the farmers on their threshing machines would ask us to please keep the racket down.
Are you sure?

[Dick Weiss]

That's what's in the manual and spec book, Ron.
The late Ray Litz made the 1st 1700 P/C kit w/the .008" clearance so the pistons would "heat-up", but my kit wore out quick
w/oil usage due to local driving and not enough "over the road" including some racing and auto-xing.

Dick

[Robin Walker]

Does anyone think that a good hone might help this cylinder ?

(from a 45K old big bore set on a 62 B Super 90 after the gudgeon/wrist pin broke)

[Greg Bryan]

Those damned gudgeon pins! I had one break on me a few years ago and it was near disaster. Fortunately I took the engine apart before it completely let go. I came out in 5 pieces ...

[Chuck Allard]

Looks more like the circlip became displaced and the wrist pin moved sideways eventually wearing a groove in the cylinder wall.

[Martin Benade]

The only help for this cylinder is a replacement.

[David Jones]

I had that happen in a 40hp VW beetle back about 1967. Blue smoke out the back and a decrease in power though going from 40 hp to 35 was probably not significant the reduction in gas mileage was. At that time it was a relatively easy fix as the local VW dealer had all sizes of pistons and cylinder sets on the shelf so all it took was a visit to the dealer and a day in the motor club on base and it was as good as new.
Most of the wrist pin was still there but the circlip was gone of course. I could not afford an engine rebuild so just replaced the piston and cylinder and changed the oil and hoped. I think that engine kept running another 5 years at 10K plus miles per year.

[Robin Walker]

Looks more like the circlip became displaced and the wrist pin moved sideways eventually wearing a groove in the cylinder wall.

I dismantled the engine and found the wrist pin had broken in half causing the damage to the cylinder. I think the little end bearing had rotated slightly so the oiling holes no longer lined up and the bearing overheated and the pin sheared.
The person who bought the car from me fitted all new rods, barrels, pistons and and an oil cooler and seriously cleaned out all of the metallic debris from the engine crankcase and the oilways. He also went back to S90 barrels and pistons.

[Steve Swift]

I have posted before about Chinese wrist pins. Lost an engine a 3K miles to a failed wrist pin so I did some testing, comparing Mahle, NPR, and AA. The Chinese ones were lighter, thinner, and way more brittle. No more Chinese junk in my engines.