Machining pistons

[edhd58]

I purchased set of pistons for my 226 off Ebay. They arrived yesterday. The ad didn't say anything about they had to be machined to be usable. Has anyone heard of this?

[Ggmac]

Originally Posted by edhd58

I purchased set of pistons for my 226 off Ebay. They arrived yesterday. The ad didn't say anything about they had to be machined to be usable. Has anyone heard of this?

It was very common . They were cam ground and came with a letter as to what cam to use . They weren't cut on the lathe .
Usually the seller will have it in the add or it will read something to that .
I saw and purchased 3 sets from bantiques, all have been perfectly ground and sized . Mine was a 21 stud flat top . A complete set was $75
He was great to deal with .
I have a copy of the instructions for cam grinding my Pistons . Each manufacturer has its own procedures.

[flatheadmurre]

Not to uncommon in the past.
Used a pistongrinder to finish to size.
Usually says finish to size between .0xx and .0xx use cam X.
Where the cam used sets the shape of the finished piston.

[Karl Wolf]

Originally Posted by edhd58

I purchased set of pistons for my 226 off Ebay. They arrived yesterday. The ad didn't say anything about they had to be machined to be usable. Has anyone heard of this?

I would look back to the listing, see if this is mentioned.
This is not a reasonable thing to sell/ buy, I have never seen a piston grinding machine. (I was in the business). The finishing would cancel out any savings in piston cost.

I would return to sender, as a defective product.

Karl

[tubman]

Originally Posted by Karl Wolf

I would look back to the listing, see if this is mentioned.
This is not a reasonable thing to sell/ buy, I have never seen a piston grinding machine. (I was in the business). The finishing would cancel out any savings in piston cost.

I would return to sender, as a defective product.

Karl

It might be a good idea to wait on this until you find what else is available.

[Bob C]

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Are these the pistons you bought? https://www.ebay.com/itm/RARE-SET-6-...p2047675.l2557
Have you measured them?

Bob

[edhd58]

Bob. Those are the ones. No i haven't measured them but the sides are rough as corn cob and the paperwork that came with them states they "HAVE TO BE CAN GROUND BEFORE USE". I checked several local machine shops and none are set up to do this.

[Karl Wolf]

I would call Egge, see what they can do.
For the price you paid, I think you may be able to do better.

Karl

[40 Deluxe]

Originally Posted by Karl Wolf

I would look back to the listing, see if this is mentioned.
This is not a reasonable thing to sell/ buy, I have never seen a piston grinding machine. (I was in the business). The finishing would cancel out any savings in piston cost.

I would return to sender, as a defective product.

Karl

When were you in the business? Semi-finished pistons were a common item at one time and a lot of shops, even fairly small ones had the tooling to finish them. Now it's another 'lost art'.

[edhd58]

Karl. Egged cant help me. Unless i want them to custom make set at a cost over 1000$

Tubman they are going back

[Ggmac]

The only advantage to cam grinding was offsetting the pin a bit to reduce piston thrust . If your stuck with the Pistons , a good machine shop can turn them . Just remember the ring groove depths usually need to be cut also .
I'm going from memory so double check . I've turned a few Pistons on my lathe and one 21 stud .040 is /was still running yrs later . Granted it was just a local car meet and home ride , weekly since 2007 . I just tore the intake off and replacing that and the carb .
All had equal comp before I tore it down .

[rotorwrench]

A guy I worked for back when I was a kid had an old Van Norman 101 piston grinding machine. The thing worked slick. We used it one time to make some old Plymouth or Pontiac pistons (I don't remember which) fit an old Indian Chief V-twin. You can get decent sizing on old odd sized cylinder walls that way . I think there is a You Tube video on that process.

I've heard of folks 4-jaw chucking the pistons offset center to the piston pin ends and taking a little bit of lathe cutting on each side but that would be way more work than having one of those old grinding machines.

There is bound to be someone out there that can still do this type of stuff but who, I don't know.

[40 Deluxe]

Originally Posted by Ggmac

The only advantage to cam grinding was offsetting the pin a bit to reduce piston thrust . If your stuck with the Pistons , a good machine shop can turn them . Just remember the ring groove depths usually need to be cut also .
I'm going from memory so double check . I've turned a few Pistons on my lathe and one 21 stud .040 is /was still running yrs later . Granted it was just a local car meet and home ride , weekly since 2007 . I just tore the intake off and replacing that and the carb .
All had equal comp before I tore it down .

Actually, the purpose of a cam ground piston is to run tighter clearances to reduce clatter when cold yet avoid seizing or scoring when warmed up. Cam grinding makes the piston somewhat oval when cold so it can expand into a round shape when warm and still have adequate clearance.

[cmbrucew]

Originally Posted by rotorwrench

A guy I worked for back when I was a kid had an old Van Norman 101 piston grinding machine. The thing worked slick. We used it one time to make some old Plymouth or Pontiac pistons (I don't remember which) fit an old Indian Chief V-twin. You can get decent sizing on old odd sized cylinder walls that way . I think there is a You Tube video on that process.

I've heard of folks 4-jaw chucking the pistons offset center to the piston pin ends and taking a little bit of lathe cutting on each side but that would be way more work than having one of those old grinding machines.

There is bound to be someone out there that can still do this type of stuff but who, I don't know.

An old Indian garage here used a lot of Dodge engine parts.
Bruce

[SUHRsc]

Funny this pops up, I have an old war era piston grinder. It was in my garage when I bought it and I shoved it under the stairway. I was just thinking yesterday what I might do with it. Maybe it's worth hanging onto and cleaning up someday for future use....

***I am not in the market of grinding pistons for anyone right now***