Zed Head

I see. It came that way, previous damage. I started in the middle of the pictures. Looks like your damper was going bad also. Do you have specs. on the engine. CR, valve lift, final displacement, etc.? I saw the general stuff but no numbers. The valve relief in those pistons has to lower CR. Just wondering. Looks like he's running 0.54 mm (0.021") "pop-up" on the pistons also. There was just an interesting thread on that a few days ago. Thanks for posting.

I'm still betting that some of the rocker arm refinishes are done by people there who don't know what they're doing. If your batch gets the right guy, awesome, if you get the wrong guy, hell. It's a simple looking job that takes a lot of care to do right. Set up for mistakes.

Serious looking pistons. Must be planning some high valve lift. Post 70 and 80 say stock stroke. Do you know why he had to massage the oil pan? Just curious.

http://www.classiczcars.com/topic/50944-want-slightly-louder-exhaust-without-changing-much/

The L28 will definitely give more power. 17% more displacement. If you're worried about CR, you could get a P79 head, then you'll be at the factory's 8.8 CR. Make sure the SU's can flow enough air to feed the L28 if you go that route. I'm not an SU guy so don't know what people do when they go with a bigger engine.

Not sure. Many people have done what you're doing though. Some say the box is fine without the floors, some say it's all wiggly and twisty. There's probably a best method out there somewhere. What I'm saying is that locking in a misalignment with new welded-in parts, then bending the box's new metal and welds to get the suspension aligned, could cause warps and bends in unwanted places. My guess is that the best way to do it is in parallel. At the same time. Weld the parts in while controlling alignment. Just bringing up a different perspective.

I think that this might be backward. Don't forget that these are not "framed" cars. They are big sheet metal boxes, kind of like an old lunch pail. AKA monocoque or unibody. Best to use the welding to hold or create the shape, not bend the welding after it's done.

"They" say that a good modification for more power is a more free-flowing exhaust system, from the manifold back. The whole thing will drop down and drag out from under a jacked-up car, Then you can hang it from the rafters in your garage. You might consider that option. Bigger pipes, larger diameter anti-resonator in the middle and a free-flowing muffler. More power and better sound. Three nuts and some hanger bolts (hooks and rubber donuts if you do it right) and you're swapped.

The stock gaskets are at 1.25 mm thickness, I believe ( I've actually measured my crushed factory fire-ring in addition to the general view). So at zero deck, about .049". Which is about where Monroe (the unofficial authority) recommends piston to head clearance. So, an 020" pop-up puts a person at .029". Which is tight. It's an interesting discussion, because most of Monroe's work is on the Z engines, not the ZX. The ZX, F54 flat-top, seems to be where the .020" (or .018" to be more exact) seems to come in to play.

All good. Still interested in how it turns out. Need to keep tabs on the best way to rebuild. You, madkaw, and siteunseen all have some work going on. Good stuff.

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.