Hi all, this is the progress report on my valve replacement in my 93 J30t. I've found a great amount of resources that I'd like to share to anybody who might be doing this job. The engine in the J30 is a VG30DE, the same (essentially) as a Nissan 300zx. Much of the information about the Z can be applied to the J, engine-wise.

http://www.pexcom.com.au/z32cms/e107_pl ... ontent.342 This link is an excellent guide to removing the cylinder heads, which contain the valves.
Youtube searches for 'vg30de', 'J30', '300zx', 'head gasket', 'upper plenum', 'valve cover', 'cylinder head', and 'timing belt' helped.
NICO forum search for any of the previous key words. Be amazed.
Ebay has some fairly economical head gasket/valve replacement sets.

In the FSM:
EM 7,8,14,15-23 (timing belt), 26, 27-36 (cylinder head)
EF&EC 6-10 (ECCS component location, vacuum hose drawing)
FE 6 (tells you there's an O-ring to be replaced between the exhaust manifold and exhaust tube)
ST 26 (power steering pump)
EL 136 (engine control harness)

A 10mm hex bit (H10) is required to remove the cylinder head bolts, and there's also an associated washer to be removed with the bolt. Careful, they like to slip around inside the head.
Removing the 14mm nuts from the exhaust manifold to front exhaust tube was difficult on the passenger side, as the exhaust tube is somewhat in the way, and required a deep socket and extension.
It's easier to just take out the EGR valve and tubing, than try to work around and pull out later. Most of those are 10mm and 12mm, and in very annoying spots.

There are seals that need to be replaced, hence the gasket replacement set. I'll be doing a full replacement, though at the least, these will be required:
4 camshaft oil seals
2 head gaskets (block to head)
2 intake gaskets (head to lower intake manifold)
1 plenum gasket(?) (yet to find a name for this, it goes between the upper plenum and lower intake manifold)
2 intake valve cover seals
Liquid gasket (exhaust valve cover)
24 valve oil seals
O-rings and seals to EGR tubes

So, I'm down to the cylinder heads, and have removed the head bolts (plus the tiny 10mm M6 bolts) and exhaust manifold bolts, as well as the power steering pump. Once I lift the heads away from the block, I plan to take them to a shop to have the valves replaced, and then I will do the rest of the rebuild. That's all for now, comments and helpful tips appreciated.

Update:

The cylinder heads and valves are off. As expected, there was some serious valve damage; eight intake and six exhaust valves need to be replaced. I improvised the valve retainer removal tool with a 19mm socket, the 6" extension, a magnet (10 for $4) from the hardware store, and a $2 rubber mallet. It appears the valve guides are in good order, thankfully. I will be measuring my heads and block for warping, and have elected to do this job myself, as the valves only need to be lapped and reinstalled.

Now, I have to wait for the replacement parts to come in the mail, so that's time to do necessary cleaning to the head and block surfaces, and the piston heads. Then I get to put it all back together! Back soon with the next report.

Update:

The parts came in the mail before Thanksgiving, so I've been able to lap the new valves, and reinstall the valve oil seals. To tap the oil seals into place, I used the female end of the 3/8" extension and the rubber mallet. Much care needs to be taken to not damage the small spring around the oil seal. All surfaces were flat, so I won't need to mill them down to fix any warping. The lapping tool amounts to a suction cup on a stick, and probably isn't worth the $8 or so that I spent on it. Perhaps a solution could be found at the hardware store for much cheaper, if budget is a constraint. A drop of oil around the cup and atop the valve helped create a very good seal, as the tool comes off the valve very easily.

Reinstalling the valve spring collets (keepers) has been the most difficult step so far, wherein only one of the two can easily be seated into the spring retainer, while the other is very difficult. This had all been done without the proper tool (I've been using a C-clamp), so I'm hoping that once I obtain the correct tool, this will be simpler. A local auto repair shop said they would lend me the tool for a small refundable deposit, after hearing my story. Just a small note, it is not recommended to leave only one keeper inside the spring retainer, as they can dislodge at any moment and go flying away somewhere(!); it's been my good luck to have found them when that happened. Otherwise, get a few extras, just in case.

After I get the valves correctly installed, I expect the rest of the rebuild to go smoothly, up to the point of the upper plenum install, where there are the many vacuum hoses and the wiring harness to reconnect. However, I am actually very worried about the head gasket placement, as there is only really one chance to do it right, once. All for now, back soon with the next report!