DPI piston orientation questions

[Jason]

I got this quite nice set of pistons and liners from DPI, and I'm wondering if anyone knows the correct orientation for the pistons. I've been trying to get an answer from Josh for the past couple of weeks, but he seems to be too tied up with the NC tech session and whatnot to answer, and I'm anxious to get started.

The pistons don't have an arrow marked on the top like the old ones. The closest thing is a * and some numbers on the bottom side of the piston. Someone (Josh or the machine shop I guess) put black marker over the * and also marked the matching side of the connecting rod. My guess would be that's the side that should point towards the timing chains. Does anyone know for sure if that's the case?

Other than the writing, the pistons look pretty much symmetrical. Does orientation really matter, and if so why?

Does liner orientation matter? There are some small notches on the outside top of the liners, and someone used black marker near the notches and 90 degrees from the notches. I don't know if those marks were meant for me or were just used by the machine shop when they honed the liners.

Also, do the liner seals go on dry, or should I use some sort of sealant of gasket maker?

Thanks


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[Shep]

I can't answer the last two questions, but for the pistons, I suspect orientation does not matter. For pistons and rods, being asymmetrical means they're off-balance, which is not exactly something you want for a part that pulsates back and forth up to a hundred times a second (6K RPM i.e. redline). I would double-check that they are in fact symmetrical, and if so install them without regard to orientation. Although aligning the numbers with the ones on the valve covers wouldn't hurt (on the valve cover, the tops of each number face the center, read from the respective side of the engine).

[Jason]

I can't answer the last two questions, but for the pistons, I suspect orientation does not matter. For pistons and rods, being asymmetrical means they're off-balance, which is not exactly something you want for a part that pulsates back and forth up to a hundred times a second (6K RPM i.e. redline). I would double-check that they are in fact symmetrical, and if so install them without regard to orientation. Although aligning the numbers with the ones on the valve covers wouldn't hurt (on the valve cover, the tops of each number face the center, read from the respective side of the engine).

The original pistons are asymmetrical when viewed from the bottom, and do have a required orientation.

14021

[Delorean Industries]

The original pistons are asymmetrical when viewed from the bottom, and do have a required orientation.

14021

Jason,

Pistons and liners are numbered accordingly and should not be intermixed. One is one two is two etc. just so there is not a mix up post a picture of the piston markings and I will mark it as a diagram accordingly.Other wise follow the shop manual. Three face one way and three the other due to the offset for the crank configuration.

Edit.... Pictures did not show up when I viewed this first. Black dot on bottom should face forward. Cylinder liner orientation does not matter. No sealer on the liner seals. Install dry per shop manual orientation. Basically though with these pistons as long as you do not mix the pistons and liners between numbers ounare fine to put them anywhere you want as long as the offsets are installed on the crank right. You can put a slug in wrong but when you look at the bottom of the piston the rod will not be centered on the wrist pin.

[Shep]

The original pistons are asymmetrical when viewed from the bottom, and do have a required orientation.My apologies, I misunderstood you. I thought you meant they were symmetrical, not asymmetrical. Still learning I guess.

[Jason]

Jason,
Black dot on bottom should face forward. Cylinder liner orientation does not matter. No sealer on the liner seals. Install dry per shop manual orientation.


That's what I needed to know. Thanks!

[Jason]

My apologies, I misunderstood you. I thought you meant they were symmetrical, not asymmetrical. Still learning I guess.

Original pistons are asymmetrical. The new ones are symmetrical. Just to make things more confusing I guess.

Out of curiosity, does anyone know why the originals are asymmetrical, and what would happen if they were put in backwards?