Zed Head

Here's a 76 wiring diagram - http://www.classiczcars.com/topic/33820-free-full-color-wiring-diagram-for-1976-280z/ Here's a link to a picture of the module connection - You might have to guess on red and green, it looks like the wires are attached to the distributor. If you get it backward the engine will still run but the timing will jump around. http://www.oreillyauto.com/site/c/detail/BWD0/CBE503/02801.oap?year=1981&make=Nissan&model=280ZX&vi=1209349&ck=Search_ignition+module_02801_1209349_-1&keyword=ignition+module&pt=02801&ppt=C0334

That makes the most sense, aside from new Paraut arms, I think. It's a shame though that Delta had a short period of time where they were grinding the surfaces off-axis, or non-parallel. There are a few threads around from the past, where people showed that was the case, real measurements. Had to send them back. They really damaged their reputation with that. Maybe had a new guy running the equipment or didn't maintain it. Anyway, it they're doing it right now, that looks like the way to go.

When you say "new rockers" what do you mean? Brand-wise. I think that might be part of the problem, The options are getting more limited. There seem to be cheap ITM brand or more expensive Paraut. http://www.stockwiseauto.com/product_info.php/cPath/1109_1277/products_id/1977610/Make/Nissan/Model/280Z http://www.ebay.com/itm/Rocker-Arm-NISSAN-280Z-280ZX-200SX-260Z-240Z-510-610-710-720-810-MAXIMA/310974615448?_trksid=p2047675.c100011.m1850&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D28808%26meid%3Dead19cd0317c4ffc8973541fc719bf9b%26pid%3D100011%26rk%3D1%26rkt%3D1%26sd%3D130906675945

Glad you're staying cool about the whole thing. Back to the big picture - I wonder if DPLLC isn't just buying rebuilt heads from the stores and reselling them. The two week lead time is really two weeks to get them from OReilly's. Might explain all of the packing material and surface rust on your last "freshly" rebuilt head. Let me know when you're sick of the whole thing and I'll stop. I can't resist exposing these kinds of people.

Yes, it seems like slightly worn Nissan parts might be better than new aftermarket parts. Probably the only thing better is brand new Nissan original parts. They also seem to be implying that the refinishing operation on the rocker arms can take off too much metal. Looks like still no guaranteed path to success on a cam swap.

Only adding this link to fill out the story. I feel like we should start a crowd-funding campaign to support rossiz's illumination of DPLLC's competency. Anyway, looks like there is another option for cylinder heads. Wonder where they come from. Actually a little cheaper then DP. http://www.oreillyauto.com/site/c/search/Cylinder+Head/02257/C0332.oap?make=Nissan&vi=1209237&model=280Z&year=1976 Who wants to be the lab rat? Post #163 of this thread from another forum is interesting also, re rocker arms and cams - http://forums.hybridz.org/topic/112117-new-cam-and-rockers-odd-looking-at-500-miles/page-9#entry1133995

Seems like this would be the match.

It could probably be drilled. Sandwich it between two blocks of wood. The early blocks and heads apparently had dead zones in the coolant passages that didn't flow much coolant. This lead to hot spots. The later design is probably just meant to keep cooling flowing at the rate that the pump could pump it and well-distributed. If your pump does 10 gallons per minute and you have passages for 50, you won't get good flow distribution. So, you could even consider improving the flow distribution in the head. But you'll have to make educated guesses. Too much knowledge to be comfortable now.

For clarity...

Comparing the Stone HG to the E31 diagram it looks like there are no issues. The gasket makers are just putting extra holes in everything. If there are two passages you get flow if not, you get a little round spot on the head. Edit - actually, what's interesting is that even the HG designed for the head has blocked passages in to the head. The bottom row has tiny holes in the gasket and some are blocked. The HG is the flow controller, not the passages. So you really need to compare an old E31 HG to a new HG to see what's what. I don't think the passages in to the head matter much.

The N42 head looks similar though.

Here's a good thread from the past that I was able to refind. Were it mine I might just punch a new hole where the E31 needs it, if the gasket material in the area is sufficient. Looks like you'll just be missing two center holes. Size might be different though. Also made a composite picture so you can see the differences. I'm assuming that the guy who put the drawings together used the proper heads and knew what he was doing. http://forums.hybridz.org/topic/115160-l6-cooling-system-diagrams/

Not really clear when the suspension was assembled. Maybe you didn't get the spring properly seated in it's perch. There's a spot for the ends of the spring coils to sit in.

Any chance you could put the gasket on the head and see what holes match?

I remember laughing inside when a friend showed me his new Toyota T(u)RD truck. This new L(i)MP one is on the same level. Maybe it's a subliminal marketing gimmick, designed to catch the eye.

You picked up a new L6 engine in Seattle?

Stepping back and looking at your whole saga, it seems apparent that the DPLLC guy doesn't know what he's doing. Or the mechanic he's using doesn't. Or both. Or he has a collection of heads in a warehouse somewhere and he just went and pulled another with the same problem as the first one. Maybe all rebuilt to the wrong specs. Regardless, it would probably help somebody out in the future to let DPLLC know that the second head's lash pads were off also. He either doesn't know or doesn't care. Maybe he's getting screwed by another guy who's rebuilding his heads. Still, he might be able to fix the problem for some future buyer.

Here's an option not mentioned often. Oliver seems to know his stuff. The page might be dated though. 2012. http://www.datsunstore.com/advanced_search_result.php?keywords=head+gasket&x=0&y=0

How long/how many miles on the plugs? How red is red? I get a reddish tint on mine, I've read that various pump gas additives can leave a residue. (Just saw the MMT page. Same.) I've found that Permatex anti-seize, the stuff in the gray tube, gums up when used on the spark plugs. Mine were harder to get out than put in. I don't think it handles the heat well although Permatex says nothing about it on the label. I quit using it there and just use clean threads and a drop of oil now. I'll bet a clean plug run in and out of the hole will clear the threads, along with a little solvent. Gasoline is a good one.

I've tried to logic out the issue of what the HG should fit and I came up with it should fit the head. Because the coolant flows from the block up in to the head, and the head cooling is more important than block cooling, I believe. Plus the fact that if there's no matching hole in the head, the hole in the HG doesn't matter anyway. The head gasket is actually designed to control coolant flow, that's why the holes are not as large as the holes they match in the block and head. As for bore size, you're really only looking at how deep the 1.25 mm gap will be at the head/block interface. It's essentially dead space that probably fills up with carbon pretty quickly and has little effect on the combustion process. Anyway, that's what my brain told me, based on information available.

Maybe Seahwaks offensive coordinator Darrell Bevell is advising DPLLC on how to choose lash pads.

It might be tunable with some tricks, and timing adjustments. Just be ready to make some changes. And don't forget that noise and power might not offset gassy smell and dead spots in throttle action, for your wife, like they might for you. Should be interesting.

Pretty clear that you've already decided... You haven't said if you've even driven the stock N42/N42 engine with dished pistons and 8.3 CR using the 1976 EFI system. So if it doesn't run right you won't know if the EFI system is out of whack or if it's the modifications you're making. You're going to end up with many unknowns on a primitive EFI system. Could be fun if you like solving problems, not so much if you like bolt on and go projects. I'd be interested in how the stock EFI system handles those changes but it will be hard to tell what's causing what. Good luck.

"green-eyed Lillith" brings up some interesting search results... So, it's looking like the loose pivot lock nut is the cause? Still curious. Not really clear how you received the head or what you did to it before driving. You have the most interesting thread going. My biggest problem right now is working up a way to modify my heater coolant control valve so I can fine tune the heat output (I have one of those Honda valves but small movement lets lots of coolant through), and waiting for a small oil leak to drop the oil level low enough so that I can add some seal conditioner (my leak-free engine started leaking). I might watch most of the game then leave for the last 5 minutes, like I did for the NFC Championship game, when they were sucking.

Bummer. Is that really a colonoscopy camera? I want one. Did you check any other cylinders? Still curious about cam timing and valve clearance. Although getting the rocker arm lodged on top of the retainer as it wiggled its way out seems reasonable also. There was probably a short period of time where the valve was still held up by the seal when piston damage could have been avoided. Sorry, I'm sure that doesn't make you feel better. Don't forget though - the Seahawks are playing in their second Super Bowl. A little bit of feel good. Unless you're from Wisconsin.