Zed Head

Here's more detail on the 240SX option. Many people have done it. It's fairly simple. http://atlanticz.ca/zclub/techtips/240sxtransmissioninstall/index.html http://zhome.com/ZCMnL/tech/240SX5spd/transmission.htm

I do. The springs hold the car up. You'll be fine and you can get a good look at it. Edit - actually you want the car on the ground, weight on the strut,you don't want the wheels hanging. The strut/shock is what keeps the wheel from dropping and the spring from extending. If you have the wheel hanging and you remove the nut that would be bad.

This just popped in to my head - some grinders use blanks to make their high performance cams. So they could keep the stock base circle. They only need to cut the base circle down if they regrind a factory cam. Looks like Schneider does either. http://schneidercams.com/dastsunL6_NA.aspx Your measurements imply about a 7 mm lift, 0.28". I think that Nissan rocker arms are either 1.5 or 1.6 ratio. So you'd be at 0.42 to 0.45" valve lift. Even with measurement error, that's not going to be a high lift cam. Cam timing is important though and that might be where any performance improvements come from. So it might be a Schneider cam, moving the RPM range for power, but it's not one of their super-duper cams, like the 300F.

What broke? That might be a clue to how a 4 speed will do. You could use the front case/bellhousing from your 5 speed to convert a 240SX 71C 5 speed. Wider/stronger gears and bigger countershaft bearing on the later models.

Some people think that the P79 head with flat top pistons has better quench/squish, which is supposed to offer better efficiency and detonation-proofing. But others who seem to know a lot say that the squish effect, even if better, is still pretty poor for the P79/flat top setup. Power measurements suggest that there's essentially no difference between the two L28 combos.

Here's more goodness from atlanticz's ancient page. Looks like 33.3 mm is the typical Nissan base circle diameter. You can measure that without removing anything except the valve cover. http://www.atlanticz.ca/zclub/techtips/valvetrain/index.html

You can mark the shaft with a Sharpie and give the nut a half-turn. If the mark doesn't move the nut is stripped. The threads of the Nylock nut are still steel though, shouldn't strip easily. It looks to me like the shaft is not through the D shaped hole. The shaft should penetrate farther through the nut, in your picture. Whatever is happening you should be able to remove the nut with the strut installed without worrying about anything dropping, to see what's going on. The shock is gas-filled and has a few pounds of upward force on it. You might be able to move it by hand and it will pop up through the hole if you get the D's aligned. First thing to do is to get that nut off of there. An air/impact wrench would work well for that since the D hole is not working. Worst case it just spins backward.

The rod moves up and down at the control arm with the suspension also, so there is a side force on the back/tip of the rod from the bushing, as the bushing restricts the motion. I think that it causes metal fatigue and that's what breaks the T/C rods. I had urethane on the back of mine for a while and the front end groaned over bumps for a couple of months then the tip of the rod finally broke off. If a person had some time they could mount just the back of the rod and move the front up and down by hand, just to feel the difference in effort required. Might be illuminating.

It does look like an error in the FSM though, the calculator is close for the dished pistons, using 1.25 mm for the gasket. 7.353. One of those CR's has to be wrong.

Here's another calculator. Gasket height has a bigger impact than I thought it would. Try some small changes there. 0.85 gets you there. http://www.ozdat.com.au/ozdatonline/enginedesign/

Where'd you get the chamber volume number?

There are some sources out there that say they have them. https://www.nissanpartsdeal.com/parts/nissan-spacer-spring~55045-e4100.html https://www.amazon.co.jp/NISSAN-ニッサン-日産純正部品-スプリング-55045-E4100/dp/B00TNL73ZW

File the flats on the nuts down smooth and parallel, Get some vise-grips like site showed or even bigger, with jaws that are in good shape. Clamp the vise-grips down very tightly on the -nut, it's half=destroyed anyway. Heat the area around the nut with a torch or a heat gun. Put some force on the vise-grips and it should break loose with a sound like it broke. If the vise-grips start to slip at all take them off and refile the nut flats and reset the vise-grips. Take 20 minutes to setup and 20 seconds to actually break it free. If you're not getting anything at the MC bleeder then you also have a problem with the seals in it. Reman quality can be pretty poor, take it off and swap it for a new reman. Probably has a lifetime warranty. "The bleeding nut on the MC for the rears didn't release anything."

I'd go to a hardware store. The good ones usually have a wide selection. You might have to stack 2 or 3 to get the height you want. When the spacer is in place it's more like a packing material, probably to keep the metal parts from rubbing together and squeaking. There's also online, like Grainger or McMaster Carr https://www.grainger.com/category/hardware/o-rings-and-o-ring-kits/o-rings?redirect=o-ring&searchRedirect=o-ring&searchBar=true

Do you mean the part that Nissan calls a spacer? They compress and deform over time anyway. You could probably use a big o-ring in its place. http://www.carpartsmanual.com/datsun/Z-1969-1978/axle/rear-suspension/13

He must be a Buick fan. https://portland.craigslist.org/clk/cto/d/vancouver-1976-datsun-280z/6973601510.html

Many people are able to leave the hood partially open and hang the gauge out of the opening. Or, if it takes a few minutes to completely die you can jump out and take a look when it happens. It can take some work but if you see zero pressure when it happens, that's a big clue. Or if you see full pressure. Process of elimination.

Don't mean to keep picking at you for more info but the time factor is important. How long can you drive before the problem happens? How long (days, weeks, months) did it run fine before things went bad? Is the pump a high quality pump or a cheap aftermarket pump? You might have a pump that's dying. Not uncommon, and they do overheat as they go bad. The tachometer needle is the best indicator of module problems.

Don't just replace the synchros on the assumption that "new" is better. I'd use the worn Nissan synchros over new inexpensive aftermarket if they're in spec. There are several stories out there from people who put new aftermarket synchros in for a rebuild and didn't like the results.

When you click on it it will download to your computer or phone. Check your Downloads area. Or, you might not have a pdf file viewer on your system. I created an image from it.

Could be that your damper pulley has slipped and the marks aren't correct, or that the vacuum hose has somehow been attached to the wrong vacuum port. Distributors use "ported" vacuum, that is only active when the throttle blade is off-idle.

A pressure gauge will tell you if it's a fuel issue. Since the problem is repeatable you should be able to put the gauge where you can see it while the problem happens. Ignition module issues usually show signs through the tachometer needle. It will read high and jumps around as the extra sparks screw things up. You're down in hot Austin so you could also have the vapor lock issue, especially since you have a different engine, maybe with some hacked up fuel system parts. Find out where your fuel lines are running. What kind of fuel pump are you using, mechanical or electric?

If he has 25 at idle he could have 43 to 47 at full advance, if that's with no vac advance. I had a couple of 22 degree mechanical advance distributors.

Still, does it really matter? If it's a radical cam he'll be able to tell by the loping "cammy" idle. If it's not radical it probably doesn't matter too much. I see multiple things happening at the same time. The path to the disassembled "wish I hadn't done that" engine.

If you're planning to remove the camshaft you might be getting ahead of yourself on the original goal. Just saying, it's easy to get diverted. People often start changing things then just get lost with a new set of problems. One small mistake and you'll be removing the head, then drilling out a broken head bolt, some broken exhaust studs, Yada yada etc.