L28 teardown, weird stampings - crank & pistons

[Chunky]

Hey guys! I'm in the process of tearing down an L28 motor. I have the "how to rebuild your Nissan/Datsun OHC engine" as well as the how to modify version. Both have been very helpful but now I've come across something that's leaving me puzzled. The motor is an N42 block/e88 head.

 

1) The pistons are stamped differently, they are all dished. Piston #1 is stamped "34" while pistons #4&6 are stamped "45", I'm not sure about the rest they are covered in doodoo build up. Searching around I've seen where the stamps indicate the over-bore but what I read said 050 for .05 over. I don't have a caliper handy(yet) to take actual measurements of the pistons/bores but I'm hoping somebody can chime in with ideas on what these stampings mean. Ultimately I'm planning to switch these dished pistons out with flats so the condition of the pistons themselves don't matter in terms of salvageability(is that even a word?) but I'm more concerned with what the stamps mean in terms of modifications already performed on the motor.

 

2) The crank is stamped P30. I think P30 is the designation for the L24 blocks but in my research another thread indicated the the part# for the L28 crank itself is P3000. That answer didn't seem conclusive from the thread. Is this true?

 

3) Last question deals more with experience rather than book information. The pistons are seized and I'd like to pull the entire rotating assembly out to have the block checked out and cleaned up if it can still be salvaged. There's a light amount of surface rust on the cylinder walls and I'm hoping that either a clean up and honing or even a slight over-bore can save it. The book stated pulling the rods/pistons out then lifting the crank out. Any advice on how to get the pistons dislodged? Is it possible to disconnect the rods and lift the crank out with the pistons/rods still in? Then possibly finesse(pound) them out? I realize that doing that will most likely leave the cylinder walls scratched and either requiring a re-bore or worse kill the block but at this point it's the only option I know of.

 

Thanks guys!

 

Ray

[cockerstar]

Start off by putting some penetrating oil in the bores to try and loosen up those rings.

It can take awhile to get them free, so make sure they're saturated for at least a few days.

 

Use a hardwood or brass drift on the bottom of the piston to free them after removing the end caps on the rods.

[Sam280Z]

To answer your last question, you can lift the crank out leaving the rods/pistons in.

Edited August 18, 2012 by Sam280Z

[Xnke]

The pistons are often marked by Nissan when assembled...the different markings on top are when the bores were fitted with matching pistons. Most OEM's don't generally do this...the block is bored and the pistons are grabbed off the line and put in. Apparently, the Nissan way was to measure the bored block and fit pistons that fit best; differing tolerances were held to a minimum this way.

[Chunky]

Thanks for the advice and info guys! It took a little bit of finessing but I was able to undo and remove the main caps and rod caps and pull the crank out. Now I'm finding that half the rods are seized in place at different angles(because of the crank orientation) I've saturated the area around the pistons/cylinder as well as the area around the piston pins. I'll let it sit for a few days keeping them wet then later this week flip it all over and saturate from the top.

 

Hoping for the best, expecting the worse...

 

Ray