Oversize Pistons

[ArcticFoxCJ]

So I just got my L28 block back and the 2 things I need are an oil gallery screen that apparently disintegrated, and oversize pistons because it was bored .50mm over.

I found a set of pistons that are .020" oversize, and I just wanted to do a sanity check... .5mm equates to 0.01968504 in, so I feel safe buying these.  Does anyone know of any gotchas I should be worried about?

[ETI4K]

Are they new or used (or NIB)?

[Diseazd]

Why not just go .040 over and not worry about it? The block screens should still be available from Nissan.

[Zed Head]

The math is correct.  That's about all that can be gleaned from your post. 

You'll want to match the pistons to the heads, not the block, to get the desired CR.  The L28 was used for small and large combustion chamber heads, the pistons were changed to achieve the desired CR.

[ArcticFoxCJ]

These are new.  (Do pistons normally come with wrist pins?  Can't seem to find those.)  

The cylinders have already been bored.  Which is fine because the pistons I found don't seem to go higher than .020 from that supplier.

They're dished pistons, and I'm still using the original head so that's good to go.

[Patcon]

Pistons normally come with wrist pins either press in or fully floating. If they're press in you should have the machine shop install the rods. They have a special oven to heat the rod so the pin presses on easily

[Racer X]

17 hours ago, ArcticFoxCJ said:

So I just got my L28 block back and the 2 things I need are an oil gallery screen that apparently disintegrated, and oversize pistons because it was bored .50mm over.

I found a set of pistons that are .020" oversize, and I just wanted to do a sanity check... .5mm equates to 0.01968504 in, so I feel safe buying these.  Does anyone know of any gotchas I should be worried about?

Whenever I have had engine block work done, I have given the machine shop the cylinder block, complete rotating assembly (crankshaft, connecting rods, damper pulley, flywheel and clutch cover). The machinist sourced and fitted the pistons. 

The machinist and I had a clear understanding of what I wanted, including the piston configuration.

I was given everything after the work was completed, including rings and bearings, and prior to assembly I checked bearing clearances and ring end gaps.

[ArcticFoxCJ]

Looks like it's a moot point.  Nobody's got 'em.  The place where I thought I'd be buying them from is out of stock indefinitely.  According to California Datsun, it's been 6 months since they last got any in, with no idea when there will be more.

[Patcon]

I always like to source pistons before machine work for this very reason...

[ETI4K]

On 6/24/2022 at 9:20 PM, ArcticFoxCJ said:

Looks like it's a moot point.  Nobody's got 'em.  The place where I thought I'd be buying them from is out of stock indefinitely.  According to California Datsun, it's been 6 months since they last got any in, with no idea when there will be more.

That's why I had asked if they were new.  My next question was going to be WHERE DID YOU FIND THEM?  I'm in the same boat.  Need .50mm over.  JE Pistons will sell forged pistons direct to you for about $200 each, and Top End Performance will sell you JE Pistons fully and correctly configured for $1300 a set.  You can bore ($200) to 1mm over and get Ross for $900 (IIRC), but they seem to not get much love, while JE's seem to be loved by "all".  Finally, you can also get Kameari from Japan for under $900, but not in .50mm over.

I've been looking for more than a year and am getting uncomfortably close to being okay with $1300 for a set.  My engine has had rods conditioned (shortened), the head has been cut, the block has been decked, it has a performance cam waiting to go in, and I am specing 10.5CR.  I figure $100 delta for TEP to guarantee proper configuration is worth it; and by getting JE custom made, it obviates buying Cometic or Kameari head gaskets at $200 to get the CR.

This is all a lot of fun.  I had budgeted around $200 for cast pistons.  😢

[Reptoid Overlords]

You guys aren't too far away from Datsun Spirit.  I think they're in Fairfax or Manassas or something?  Maybe reach out to those guys and see if they could make some .50 over.  At least you could go pick them up yourselves possibly.  Prob just as expensive as the others. 

[Zed Head]

Piston availability has varied over the years.  Here's an old post about alternatives.  Takes some extra work.

https://www.zcar.com/threads/honda-xl500-pistons.45301/

Datsun Spirit has possibilities too.  Expensive of course.

https://www.datsunspirit.com/shop

And Rebello might have something.  Haven't seen much written about what's happening there, but if he's still building engines he needs pistons.

http://www.rebelloracing.com/nissan1.htm