I am assembling a 1990 engine and have encountered something that has stopped me in my tracks while inserting the pistons.

Inserted and hand tighten the # 1 piston's cap. Crank spins with little effort.
Inserted the #5 piston and the rod end binds against the #1 rod and creates a lot of resistance while trying to turn the crank - tighten the #5 rod cap and the crank will not turn.

The engine was fully disassembled when I got it and the piston order was lost. I have assembled an other 928 engine (86 s3/hybrid) and had none of these issues. I assumed all rods are manufactured to same width. Bad assumption?

Everything is new - thrust bearing, rod end bearing, nuts and piston rings. Well lubricated.

Any guidance is appreciated. I am tempted to mic the rods.

 

Are the rods facing the right way?

 

Piston arrow points toward pulley (WSM).

 

Kevin, I recall a similar experience on my 944. The caps were installed in the wrong direction. Turned them around and binding was gone. Harvey

 

The narrow sides face each other...IIRC.

The rods are all the same.

 

Good one. Numbers need to match and their stampings go on the same side of the rod.

 

I was following the text on WSM page 10-24c that says the arrow points towards the belt pulley. I must have missed that additional instruction.

 

Matching numbers I was aware of. They all match.

 

I suggest checking on this. One thing's for sure: the wide sides don't all point the same way. The rods on each side are assembled differently with respect to where the piston notches are.

 

Check the manual, 13-15, Installing Pistons & Connecting Rods.
Is it possible that someone took the pistons off the rods and reinstalled at least one of them backwards?

 

thats what im thinking... easy to do for guys that dont do it every day

 

I cannot speak to that - Porsche dealership pulled the engine and the PO did not touch anything.

So, one page says the narrow sides face each other and another page talks about the piston facing another. Wow. I assumed the rods have never been separated from the pistons. So, the next question is do I need to flip the rods 180 dg?

Yikes.

 

pictures!

 

Definitely sounds like the crank fillet is being pinched. The chamferred side of the big end has to be facing the crank throws (outwards) on both rods.

 

I wouldn't assume anything. Look through the manual carefully, there's enough pictures you can reference to allow you to see if the pistons are on the rods correctly. Or like Mark said, post some pics.