Another Z to see the roads again...

[ETI4K]

The other pistons are within a couple of grams of each other - let's just say 2.2 grams on average.  In comparison then, the variance is an order of magnitude lower.

The machine shop says the rods were balanced to within 1g, and I'll bet no attention was paid to balancing the ends.  I plan to confirm, just haven't done it yet.

Edited July 7, 2021 by ETI4K

[siteunseen]

I was able to do mine as the hole assembly. I have an older set of triple beams that I put a railroad spike on and that let me do the cups and rods, caps. Without that added railroad spike it maxed out the triple beams. 

To get weight off I ground on the outer sides of the rods. Got them all to weigh the same amount of grams. Seems like it was in the 700s maybe? That's almost 2 lbs each. 448 grams per pound.

Edited July 7, 2021 by siteunseen

[ETI4K]

Trying to keep this restoration going strong is a bit of a trick.

I have to do enough work/investigation/reading about the next task in order to hunt down and order necessary materials so that when I am ready to actually start that task, I have what I need in hand.  All of this of course while doing the previous task and dealing with the where to get and how to do that I didn't plan on.

The latest is the ZX throttle body.  Not ready to rebuild it, but I know I need some parts because I took it apart several weeks ago to see what kind of shape it's in.  I actually removed the staked caps at the ends of the throttle body and found one bearing was iffy and, since I damaged one seal getting the cap off on one side, I'll replace the both u-cup shaft seals.

They are 10 x 16 x 3.  I have been searching for months to no avail, but a few days ago I stumbled upon Allied Metrics.  They will make them, in any material I want with only a 10 piece minimum.  Not bad until you consider they want $23 EACH.  Still looking...😪

[ETI4K]

So no one wants to venture a guess as to which piston is heavier?

I just found some new ITM pistons in stock (finally) - pistons, pins, and rings: $215 at RockAuto.  My only other alternative is forged at around five times that.  Talk about being conflicted.

[siteunseen]

The ITMs are lighter. I've got .030 over sized and way back when I did my research they were the lightest of the small group, maybe not a group just all that was available at the time. 

Don't forget to get an aluminum flywheel if you're going to do a weight watcher build, you won't regret it. I did a balanced weight and it was easy and fun to balance half the bottom, didn't touch the crank. Then balancing the valve train was the fun part, literally fun. I shaved the parts then wire wheeled them to be slick all around. Did a good cleaning after that with lacquer thinner then wiped everything down with good wheel bearing grease. Kinda proud of that if you can't tell. 

Edited July 13, 2021 by siteunseen

[ETI4K]

Yep.  Lightweight clutch assembly and flywheel.  Stayed with steel for the flywheel, though. 

Balancing valvetrain parts does sound like fun, and that'll come soon enough, I hope.

Right now I am trying to get the short block built.  I just now located sets of Taiho rod and main bearings, .010 under, in Australia of all places.  I sent an email to Taiho requesting info on materials used.

I have not been able to find any other bearings by any mfr.

[ETI4K]

Good news for anyone looking to get bearings from Australia 🙄.  The Taiho bearing set arrived a month early.  Now on to the pistons.

So, a new set of cast pistons, distributed by ITM, arrived from RockAuto.  I still can't get the actual weight, but I did measure the differential between the lightest and heaviest - better than 2.2 g.  I am looking at the underside of these and not feeling good about trying to remove that much material.  I know I can chamfer certain edges, but I'm not at all certain that'll be enough.  Beyond those edges it gets a little sketchy.  There are two bosses on the sides of the piston below the pin that look like decent candidates for material removal.  Problem is that if I start on it and can't safely get it to weight, they're mine forever and I have to buy more - of the same brand and likely problems.

 

Note the nice little nick - fresh from the box.

It's looking like I'll be into forged pistons to get a decent set.  I really wanted to avoid THAT expense.

 

 

[grannyknot]

So if the difference between the new pistons is less than 2.2 grams don't you think there is enough meat on the 4 corners where the arrows are pointing to be able to even them out ?

 

[ETI4K]

Those corners wrap around steel inserts (dark grey).  Not sure if removing material could free the inserts under loaded conditions.

[Mark Maras]

 I don't know if it's recommended but many years ago a friend and I matched piston weights by add TIG weld to the inside of some of the pistons. It was a weird project. 510 pistons in a 128 FIAT engine to bring it up to 1300 CCs. (The wrist pins were the same size) It worked for us.

[ETI4K]

Very cool idea.  That had to be fun building that motor. 

Could even add some steel to those inserts easily with MIG.  Then I'd just sweat it out the first few hundred miles hoping nothing went screwy.  So the cost of insurance against sweat (that sweat anyway) is $800 ($1000 forged - $200 cast).  🤔

[grannyknot]

6 hours ago, ETI4K said:

Those corners wrap around steel inserts (dark grey).  Not sure if removing material could free the inserts under loaded conditions.

Gottcha, didn't know those were there.