How to provide oiling to the piston pin in a forged piston?

[PackardV8]

Only slightly OT, but in the discussion about pin oiling, my machinist, who does many OEM builds, says the Fords are the worst; if the piston/pin interface isn't carefully oiled after rod installation but before short block assembly, some of them will gall and lock up on start. Once successfully started and run, there's usually no further issues.

[Bos's5.0]

Only slightly OT, but in the discussion about pin oiling, my machinist, who does many OEM builds, says the Fords are the worst; if the piston/pin interface isn't carefully oiled after rod installation but before short block assembly, some of them will gall and lock up on start. Once successfully started and run, there's usually no further issues.

Well it's a good thing Ford only built one engine, because narrowing down what you are talking about if it were a GM would be impossible.

[modok]

I know what he means. The older ones that used a soft brass bushing expanded into a rough bore. Don't know when they quit doing that, but not soon enough

[dwilliams]

What's the recommendation here?

I use the "four small holes tangential to the pin bore" pattern. It oils the pin from the sides, and the holes are easier to drill than trying to come in from under a ring and remove less metal than a big hole in the bottom. I pick the hole size by the scientific method staring at the drill index and deciding "this looks about right." Usually 3/32 to 1/8".

[dwilliams]

The older ones that used a soft brass bushing expanded into a rough bore. Don't know when they quit doing that, but not soon enough

Sounds like the FEs. Ford used a ball broach to swage the bushings into place.

The pin bores were often loose, though I don't know if they were oversize to start with or they used some lowball bushing material that didn't last long. Ford didn't bother with "quality control" much on the FE engines, or at least not on the later ones. I am certain the factory decked some of those blocks with a chain saw...

[4vpc]

Old thread I know, but IMO the best way is to look at a modern engine and see what they do. One I looked at the other day had 8 oiling points per piston, some of that is because it had the pin pressed into the rod. It had two grooves, one hole drilled below and one from the oil control ring groove down into the top of the pin.

[Walter R. Malik]

On another thread, I was alerted by dwilliams that in the bad old days Venolia forged pistons were shipped with no provision for pin oiling. A very good head's up, as we've become so accustomed to pistons being good to go out of the box, that these NOS caught us not looking. They required pin fitting and now will require oiling mods.

I know the several ways this is accomplished; easiest is just drilling holes through the bottom of the pin boss. Most difficult would be replicating those with four grooves milled inside the spirolok grooves without touching those.

What's the recommendation here?

I would say any way you can without measurably weakening the piston.
I don't think you could have to much oil there.

[ptuomov]

Quick questions on the wrist pin oiling in a conventional crankshaft guided rod setup. How important is the side clearance between the piston wrist pin boss and the rod small end to wrist pin oiling? Should I go for minimum clearance there that crankshaft end allows and trust the piston on the one hand and the rod on the other hand to take care of their own oiling requirements? Or is there a meaningful benefit from leaving more of the pin exposed to splash oiling?