Zed Head

How much piston pop-up? Are those ITM pistons? Hope it all sticks together this time.

I think we're on the same page, as is redzed. His builder has a comfort zone, as he should. Good info though on the ITM L24 pistons. They are, apparently, .020-030" taller than stock Nissan pistons. Whether it matters or not. That's what I got out of the thread.

Let's take a breather and get back on track. The guy doing the work on this engine apparently wanted a zero-deck. So he felt like machining the pistons was the way to go. Sounds like he was working off specs. and not off what "could be". He probably would have been okay with leaving the 020" pop-up.

No biggy, just a smally on your comment to madkaw, Especially since you edited close to the time he asked. Anyway. The ZX F54 flat-top piston engines all seem to have a pop-up of about .020". But there doesn't seem to be a lot out there about the early L24 flat-top engines. Maybe they're zero pop-up (I'd use "deck" but it's hard to keep the +/- signs correct). But they both use a similar gasket thickness so your .020" pop-up probably was fine. The 030" that Diseazd had might have been in that worry zone, but even then, some guys like to run a really tight squish distance. But that's with forged parts to minimize stretch at high RPM. To top it off, somebody (madkaw maybe?) said that Rebello thinks the ZX P79 cylinder head "squish/quench" design was poor. So, overall, it seems that keeping the pistons from hitting the head might be the main concern. From there, you can get in to forged parts, and RPM, and all kinds of details. Shaving the pistons for insurance is probably the way to go. Too bad ITM is producing out-of-spec. product.

Thanks for being honest. You were being misleading in your post above, to madkaw, though. Not good.

Did you edit this? Because I went back and looked about an hour ago and I was sure it said "about 30 thou". And I had the same question as madkaw.

There's something about the formats and layouts of the various forums that affects the replies, I think. The zcar.com forum tends to make a person cranky. It's primitive and clunky and dull,and leads to irritated responses. Hybridz seems more serious and, like serious people do, leads to simple questions being ignored. This forum is just generally pleasing to use and look at and has that affect on the replies. It will be disappointing though when Davidz1911 comes back with another problem. I'm going to guess that the AFM plug was loose and the engine was only getting idle speed fuel from the ECU.

What did you find? You might be back in two days. We like to know the details, otherwise it's like watching a movie with no ending. Plus, it will help out the guy or gal with a similar problem, in the future.

Your symptoms sound like a loss of fuel pressure. Fuel flow is one thing, correct pressure is another. You need to measure pressure while the problem happens. Stick a gauge on and watch. Fuel pump motors and relays can get hot as current flows and stop working correctly. I've had a fuel pump that did that as have others here. The pump created pressure for about 5 minutes then it slowly died away as the motor stopped spinning. I thought your post looked familiar. You've changed some things but no big deal. Pretty sure I didn't call you an idiot on the other thread, it took me a while myself to figure out the Z's EFI system. The key is actually measuring things. Corroded-looking connections can be fine and clean ones can be bad. You'll waste a lot of time and probably create new problems "fixing" things because they look bad. Best to measure and confirm first.

EGR could be sticking. That would lean out the mixture (actually not "lean" but "charge-deficient"). Try turning up the idle speed screw to see if you can keep it running while you diagnose things. By the way, you described a "won't stay running" condition, not a "won't start".

$272 Canada is $216 US. $72 Can. is $57 US (today). Typo in the calculator?

Seems like one of the reasons that people like to work with Rebello or DatsunSpirit is because the owners share what they know and the customer learns something when it's all done. Your guys seem more like the old, classic, "leave it there and we'll call you when we're done" kind of guys. Guys that always come in at the top end of the quote range and call you with "problems" found requiring more work. I think the descriptive word is sketchy. On notching the block, a general trick that I learned from a machinist is to turn the block upside down. The grinding or filing chips will fall away from the cylinders. That's if you're planning to leave the block assembled.

Saw this on zcar. They're standard bore so if you go over not much use. But might be useful if the bores are good but pistons not. http://www.zcar.com/forum/19-sale-parts-accessories/367049-nos-piston-wrist-pin-set-l24-flat-top-240z.html Tried to learn what "Ttt" means but all the internet came up with is "third tier toilet". Not sure why he says that... Also, just because it's interesting - http://www.art-piston.co.jp/en/profile.htm

The rocker arms generally follow the cam and the individual lobes. On the towers, the thought seems to be that if you can move things around to where the cam spins freely you're good. That's what I've seen described. Otherwise, you'd have to get a new set of cam towers when you bought a new cam.

Those are good points. The one about the cam turning freely and align-boring is one of those areas where Nissan and the rest of the world seem to disagree. Nissan would have you replace the whole head, but there's much written about tapping the cam towers when installing to get them adjusted so the cam will turn freely. People swap towers all the time apparently.

It should be fine. The oil flow is controlled by a restrictor in the head gasket, not the passages in the block or head or towers, and the size is the same for spray bar and internally oiled cams. And the oil pumps are the same also, old versus new. So the same quantity of oil is flowing to the cam towers. From there, oil flow and pressure is controlled by either the holes in the spray bar, or the holes in the camshaft. But they both start with the same amount.

Tapatalk is associated with your phone, It's an app. It's not necessary. What happens when you click "no" to the question?

Yeah, it is interesting, The guy that makes them has been around for quite a while and seems to know what he's doing. But Nissan used to make a one-piece arm, with a chrome-plated rubbing pad, and they switched to the brazed on pad made of more wear-resistant material. So even if the loads are handled fine you have to wonder about longevity.

Could spend more - http://www.zccjdm.com/catalog.php/azcarbum/pd2120660

Not to pick on your builder but he could mock things up with your old gasket, or no gasket and some math, and some clay or soldering wire, and actually measure the clearance. Most of us get disturbed because we don't have the experience or the tools but this should not be a big deal. If he came to you and said "the new pistons are only .015" from the head and that's a problem" that would make sense since there are general guidelines/thoughts on that clearance. But the consternation over .007", right off the bat, seems odd. Either you're not getting the complete message or he's getting disturbed over something he shouldn't be. Anyway, it's all part of the game.

Once you get started you'll find that it's really not too hard to get the wires right. Even with a complete diagram, you should always check your wires with a meter or test light, just to be sure. It's a bad feeling to watch smoke rising or see sparks when you decided to just take a chance and trust somebody else's write-up or memory..

Disturbing. Their web catalog of services says that they work on 81-83 L28's, which all have a pop-up of ~.020". He shouldn't have been surprised and should have compared to the old pistons right away. Not really clear what the problem is. If the new ITM's are just a hair off the old, what's to be right pissed off about?

That is ever so much clearer. Kidding. Kind of. Seriously, you need numbers. Really though, your engine builder should be familiar with this and know how to deal with it if he's experienced with the engines. Nissan pistons are all essentially the same except for flat-top versus dished. Did he say it was a problem or just mention it in passing?

If there is nothing special about the sealing edges of the water passages in the gasket, I would just drill the newer gasket to match the older. Clamp the gasket between two blocks of wood. It's a common method to prevent tearing or chipping of sensitive material. Or carve the holes out with an exacto knife. Not as hard as it seems, if there's no metal layer.

Which is old and which is ITM? You don't really say which is which. There's much written about L28's and piston pop-up of about .022" but I can't find much on L24's. BRAAP measured a bunch of L28's with flat-tops. Post #19. http://forums.hybridz.org/topic/58127-best-way-to-achieve-piston-to-head-clearance/