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G'day all, have been into Packards since 1966. I started stripping them down in 1967 and on assembly noticed that the piston split was assembled toward the camshaft..against common practice. I read that this was because Packard had followed the "de-saxe" engineering principle and slightly offset the crank..the theory was and is that the engine is less likely to stall when idling slowly. I can understand that this would not be highly publicised as Packard could keep this little "edge" to itself. Does anyone have any Packard dialogue on the subject. i recall reading in an SAE Paper about 40 years ago of this "wrinkle". It was also used by Standard Motors of England. Anyone out there any the wiser? PT

General engine practice is to place any piston split or T-slot opposite the thrust side of the cylinder because the slot makes for the weakest sode of the piston. Has nothing to do with cam location. Cam maybe mentioned in field service documentation for quick reference only. The.thrust side of the.cylinder is the side that the rod journal passes under FIRST



So assuming most all engines turn clockwise (looking at front of engine) then the split or t-slot should face right side (US drivers side).
I doubt that the desaxe crank has any influence on the posjtion of the piston slot.

It is always critical to look for any gudgeon pin offset of the piston. It can be very subtle from as little as .020" to as much as 1/10". Variations can exist between oem and replacement stock. Some pistons may have no pin offset at all. Especialy on engines made prior to the 55 HP revolution.

The desaxe crank was primarily to lessen the posdibility of of breaking ones arm when hand cranking was was still popular. Maybe double check me on this but even tp this day many small engines such as lawn mower engines with pull or kickstart are desaxe. Desaxe only applies to inline engines. I dont thonk it can apply to v or opposed cylinder engines.

Regarding the positioning of the piston expansion slot, this from the 1934 Service Letters.

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Many thanks Owen for posting the service letter.
My guess is that later change would have most likely been to reduce oiloil consumption: Clockwise turning crank throwing oil at the slot in the earlier fitment of the slot toward the left side.

In either case, any piston should always be checked for pin offset. Especialy modern replacement pjstons.

Footnote: apparemtly tbe oem pistons referenced in the service letter were assumed to have ZERO pin offset. Reasonable assumption for the prewar era.

PackardV8, there are plenty of Packard automobile engines that I've not had apart, especially from the very early years, but I can't say I've ever seen one with offset piston pins - are you saying you're aware of ones that do?

I realize this is a different question than the one originally asked about crankshaft offset.

My only claim is that REPLACEMENT pistons, especialy of any modern manufacturer, especialy of the POSTwar era is very likely tho not necessarily have offset pins.

According to the service bulletin u posted above then any Packard supplied pistons would have NO offset.

I have a late 40's non-Packard engine that factory spec was no offset. However some replacement pistons do have offset pin and othrr replacemrnt pistons have no offset. Just depends on suppliers.

Bottom line. I always check for offset pins unconditionaly.

The des-axe issue raises another question: how long did Packard continue with the desaxe crank. Maybe thru 54????