Coopere
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- Feb 11, 2015
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Hoping someone can shed some light on this,
I am in the midst of a cylinder replacement away from home base, due to stock availability in the area we have had to purchase a superior cylinder assembly with new piston. Now the engine was last overhauled in 1994, and we pulled off a chrome cylinder that had a superior piston installed ironically. This work was done prior to my ownership. Now in looking at the new cylinder and piston we realized that it looks like the following service bulletin applies,
https://www.lycoming.com/sites/default/files/attachments/Piston%20Pin%20Identification.pdf
we placed 2 calls to lycoming technical support today but can't get a definitive answer but we believe piston pin p/n 69650 had previously been installed and can not be re used. Lucky we had ordered a superior piston pin and had it on hand for the install.
However this brought up this discussion, since we believe a thin walled piston pin was installed Lycoming stated that a thick wall piston pin can't be installed unless all cylinders are removed and checked due to the weight differences I believe between thin wall and thick wall piston pins. The pin that came out does not have the * or the dot tooling marks that we can see however the pin is old (1994 likely) so its difficult to know for sure.
So we weighed the units and this is what we have found out
Old piston pin and caps = 386 grams
new piston pin and caps = 400 grams
this leads me to believe since the older pin is lighter its the thin walled unit but once again Lycoming couldn't provide dimensions of the 69650 pin since its been superseded by
lw-14078
this is a pretty big weight difference
Now it gets more crazy,
The old piston weights 1363 grams (its a superior ironically)
The new piston weighs 1355 grams (superior supplied with the cylinder assembly)
So the total weight of the piston, pin and caps and rings as follows
Old = 1750 grams
New = 1754 grams
so a difference of 4 grams but on the heavy side.
We have been searching all afternoon and can't seem to find any actual published weight limits so far for install, continental states no more than 14 grams difference but they are not Lycoming.
We have read the service documents pertaining to lycoming match sets of pistons but since this is a superior unit it yields no help without publishing the actual weight tolerances.
Im hoping someone has run into this and can shed some light or pass on some information, we are at a stand still, the opposing cylinder has been replaced from the original chrome and it was done well after the 2006 piston pin sb I posted above, its a lycoming cylinder and piston but I have no idea what pin is installed without pulling it but I would guess it has the new style pin since it was done after the sb so it should by rights have been corrected.
Its an Io-540-c4b5
Hoping for some constructive help.
Thanks everyone...
I am in the midst of a cylinder replacement away from home base, due to stock availability in the area we have had to purchase a superior cylinder assembly with new piston. Now the engine was last overhauled in 1994, and we pulled off a chrome cylinder that had a superior piston installed ironically. This work was done prior to my ownership. Now in looking at the new cylinder and piston we realized that it looks like the following service bulletin applies,
https://www.lycoming.com/sites/default/files/attachments/Piston%20Pin%20Identification.pdf
we placed 2 calls to lycoming technical support today but can't get a definitive answer but we believe piston pin p/n 69650 had previously been installed and can not be re used. Lucky we had ordered a superior piston pin and had it on hand for the install.
However this brought up this discussion, since we believe a thin walled piston pin was installed Lycoming stated that a thick wall piston pin can't be installed unless all cylinders are removed and checked due to the weight differences I believe between thin wall and thick wall piston pins. The pin that came out does not have the * or the dot tooling marks that we can see however the pin is old (1994 likely) so its difficult to know for sure.
So we weighed the units and this is what we have found out
Old piston pin and caps = 386 grams
new piston pin and caps = 400 grams
this leads me to believe since the older pin is lighter its the thin walled unit but once again Lycoming couldn't provide dimensions of the 69650 pin since its been superseded by
lw-14078
this is a pretty big weight difference
Now it gets more crazy,
The old piston weights 1363 grams (its a superior ironically)
The new piston weighs 1355 grams (superior supplied with the cylinder assembly)
So the total weight of the piston, pin and caps and rings as follows
Old = 1750 grams
New = 1754 grams
so a difference of 4 grams but on the heavy side.
We have been searching all afternoon and can't seem to find any actual published weight limits so far for install, continental states no more than 14 grams difference but they are not Lycoming.
We have read the service documents pertaining to lycoming match sets of pistons but since this is a superior unit it yields no help without publishing the actual weight tolerances.
Im hoping someone has run into this and can shed some light or pass on some information, we are at a stand still, the opposing cylinder has been replaced from the original chrome and it was done well after the 2006 piston pin sb I posted above, its a lycoming cylinder and piston but I have no idea what pin is installed without pulling it but I would guess it has the new style pin since it was done after the sb so it should by rights have been corrected.
Its an Io-540-c4b5
Hoping for some constructive help.
Thanks everyone...
