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The only engine building manual I have is for a 2L engine and shows an arrow on the piston crown, which is supposed to point toward the exhaust side of the head. The 1600cc piston/liner kit which I purchased from IAP has no such marking, and the piston itself seems to be perfectly symmetrical. I spent some time with them on the phone this morning trying to understand which way the piston is supposed to go in the bore and as far as we can tell it does not matter. Obviously I'd like some level of confidence that this is accurate. Does anyone out there know if there is right or wrong way to put the pistons in the bore on a 1600cc engine? They're stock compression pistons, and made by AE/Borgo.

-tj in Los Gatos
 

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I believe the difference is in the vertical rod that goes from the piston to the crankshaft. It is aligned towards one side. It is important that it is placed in the correct position, otherwise the bearings will get damaged.
 

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Hey TJ - just stuff a BMW M30B35 in there, and get some real power!

Kidding aside, I believe those early 1600 pistons were symmetrical, so they can go in either way. As you note, there are no markings on them that could be used to indicate an orientation.

As Rafael points out, the rods have a definite orientation, but your 2L manual will describe that - its the same for all 101 - 105 engines.
 

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Thanks guys. I do indeed have the information regarding the offset of the conrods, so all is well there. It does appear that the pistons on the early engines are symmetrical, so unless I hear differently, that's what I'm going with.

-tj in Los Gatos
 

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Yep. Offset pin came in partway through 1750 series; 1600 piston is symmetrical. Put the pin in and measure the length from one side of the piston to the far pin side, then vice versa. If they're equal, the pin is not offset and it doesn't matter.

This assumes the pistons you're using have identical valve cutouts on the top. If one's larger, that's the intake side.

Andrew
 

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Hi Andrew,

I measured the cutouts for the valves and they are indeed identical. I'll measure wrist pin to piston side just for good measure, but I'm certain they're symmetrical slugs.

-tj in Los Gatos
 

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Just to revive this old thread and add a new twist, I believe I read somewhere that stock GTA pistons, have an arrow on them that must be pointing forward, can anyone confirm?
 

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I knew that, was more a question of the arrow facing forward which seems proprietary to the GTA pistons, as most offset pistons have the arrow pointing to the exhaust side, but ty.
 
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