NewZed

You might run that pressure test again, or a leak down test A slanted motor shouldn't cause a 17% drop from high to low. Reporting the values from all cylinders would tell more also, not just two. That link works. Sounds terrible. Good luck.

Link doesn't work and youtube is misspelled. If you get the head off again maybe you could rig up a drill motor to spin the cam on the bench. Should be enough oil already there to keep things lubricated and you can watch each valve moving. Support the head by the ends and the valves can open and close freely. Or stand it on end. A piece of hose from the drill chuck to a bolt head makes a good flexible coupler. Have you done a pressure check to make sure each valve is closing properly? Maybe you've got a bent one that is hanging and getting dinged by the rocker arm.

Maybe your problem is related to why Nissan went to a dual-cone synchronizer. Might be cheaper in the long run to take the bellhousing from your ZX trans and do the 71C conversion. It would be interesting to see what the friction surface looks like on the 2nd gear ring when you take it apart. Another thought regarding the blocking ring is that all "brass" may not be the same. In other words, the coefficient of friction may be different between Nissan rings and aftermarket rings. Maybe just replace the 2nd gear ring with a factory Nissan ring. They're about $50 at courtesyparts.com. Edit - one of these might buy you a few RPM also - http://www.courtesyparts.com/nissan-motorsports-roller-bearing-pilot-bushing-p-341365.html

That's pressure that you're reading, not compression. The gauge used can have a big affect on the number you get. The big tubular adapters that come with some gauges can drop the pressure reading by 60 psi. The adapter tube and gauge volume get added to the combustion chamber volume so the effective compression ratio drops.

If you're going to try some other fluids, the Swepco/ATF blend is definitely worth a shot. Fluids have a big impact. I had an old 78 5 speed that ground the 2-3 shift with Valvoline 75/90. Redline MT90 fixed that problem. Then I tried the MT90 in an old 1980 5 speed but still had a problem, with 1-2 and 2-3, so tried the Swepco/ATF blend. It raised my RPM limit before gridning, by about 1200 RPM (memory, may not match previous posts) over the MT90. This is on old worn, or rusted synchros, so may not apply to new. I used the Swepco based on JMortensen's recommendation's in past threads. He has a lot of history with the blend at 50/50. 50/50 felt a little thin to me so I upped the Swepco to 75%. Not cheap though, about $15/quart. The newer "syncromesh" type fluids are thinner, about 30W, from what I've picked up on the web. You need some higher viscosity to get things spinning, and the materials and synchroniser pieces are designed aorund a certain type of fluid. Re johnc's comment about new fluids in old design transmission's.

Did you rebuild with Nissan baulk/synchro rings or aftermarket? I've seen internet reports about "problems" with the less expensive rings although details were sparse. And did you record the ring/gear clearances, just for comparison? Was the 2nd gear clearance similar tothe others, or on the high or low side? I had a similar high RPM shifting problems with an old junk yard transmission and found that the Swepco 201/ATF blend was significantly better than both MT90 and Valvoline 75/90. I ended up at 75/25 blend. Just one more anecdote.

The first page of this thread will answer a lot of your questions - http://forums.hybridz.org/topic/49194-differential-cv-lsd-hp-torque-r160-r180-r200-r230-diff-mount/ The R200 mustache bars are out there, typically from $50 to $75. Hardly worth messing with trying to drill spring steel (see the thread above, first page). As johnc inferred, your and other's, and my, difficulties come from trying to save money by using existing parts and puzzle-piecing it together. Study the Modern Motorsports parts below, and the link inside with the install pictures and you'll see pretty much everything that needs to be considered. The first page of the link above shows some shortnose R200 install parts also. http://www.modern-motorsports.com/catalog/product_info.php?products_id=74&PHPSESSID=9e25b7fab3e9baf204ae3aa017e3d66f I have also read that the stock control arms may interfere with the big flanges on the short-nose diffs. Most people seem to have aftermarket control arms for this diff swap. One more thing to watch out for. It was noted in the Pathfinder axle threads.

The 280Z body style changed in 1979, with the ZX (in the States). None of the ZX drivetrain mounting hardware will work on the Z car, except the two studs in the cover and the holes for the front mount. The ZX's don't have a mustache bar. The only good differential part you'll get from a 79 ZX is the differential assembly itself, which might be a longnose R200, but could be an R180. It's been proposed that the diff and its carrier from the shortnose Q45 R200 (which you most likely have) will swap in to the long nose R200 case with its ring and pinon gear intact. You might need sleeves for the botls thoguh. This allows you to use typical longnose R200 hardware to bolt the diff in to the car. Then you need half-shafts to get the power to the wheels. The most difficult and/or expensive part of the swap seems to be getting half-shafts of the right length with the right bolt pattern. If you come up with a good inexpensive plan I'm sure it wil be popular. I've been through most of those threads and every now and then they'll get brought back to life. Somebody with the Pathfinder axles blew up a CV joint when the axle shaft pulled the joint apart. His adapter thickness was off a little bit, not thick enough. There's a recent thead on a similar problem with the Modern Motorsports kit. He didn't have an adapter but had custom shafts, the joint pulled apart. Good luck. Take extra care on those half-shafts.

.390" = 9.9 mm. That's what the atlanticz table shows for exhaust valve lift for the J cam. You're actually measuring .4 mm over what's shown for the M cam. Odd. It's also odd that the part numbers both end in E4126 for the L24 and L28E A cams, in the table, and show the same specs, but the FSM numbers are different, 11 mm vs 10.5 mm. Maybe someone assumed that the A's were the same. Just goes back to verifying what you read. Maybe someone could start a "measure your valve lift" thread and get some more verified numbers. Just for fun.

Looks salty. There must be some kind of reason. Four intake runners feeding six ports seems a little weird. I like the custom bracket for the nylon zip tie. Probably a weight saving measure.

73 shows 11 mm also. I've looked before and can't find the ZX (P79, P90) numbers in the FSM's, so can't compare those. Who knows from where the numbers came.

10.4 mm vs. 10.5 mm - atlanticz table vs. 1978 FSM data. I thought the topic was about the validity of the data in the atlanticz table, not driveability. You said the atlanticz table was completely inaccurate and we're trying to determine if that's true or not.

Too bad there are no references on the atlanticz page to tell where the information comes from. The L28 A cam specs in the table are 0.1 off from the 1978 FSM, so probably not copied from there. Somebody must have measured or has another document to work from. 0.1 is pretty close though. One A cam measurement shouldn't be enough to paint the whole table as completely innaccurate though. That would be some radical extrapolation. Picture from the 1978 FSM Engine Mechanical chapter:

This site is pretty handy and suggests that one part is pre-5/77 and the other after. Click on Part #5 and you'll get another window. http://www.carpartsmanual.com/datsunS30/DatsunZIndex/Engine280Z/EFI/AirFlow/tabid/1614/Default.aspx

Thanks for clarifying my misinformation. I had originally written a comment that it seemed odd that MM would sell an axle that was too short, but edited it out. But that does appear to be the case. When a car at stock height hits a bump it will drop or rise to the height where the joints pop apart momentarily so too short is too short no matter where your ride height starts. If the axles are designed to work with the adapters then MM must have bad information on how long the axles should be to work right, since they come as a package. Weird how this stuff happens. Good luck to the OP on getting it working. Seems like there aren't many easy deviations from stock when it comes to the rear drive shafts, everyone has problems.

Be careful if you decide to buy a "new" Q45 axle from a parts store for the CV joint. "New" means a totaly different design, that will only work with the manufacturer's shafts. Only "rebuilt" will have the Nissan design. You said that that the PO said you had MM axles. I don't see that MM sells a CV axle/center bar/shaft. Maybe the PO meant 5 lug axles as shown on the MM page - http://www.modern-motorsports.com/catalog/default.php?cPath=32_53 You probably have the two short shafts from a Q45 and the same problem that SUNNNY Z and RB26 had. Interesting problem, those two drive shafts seem to be a lot more trouble for everybody, than you would think from looking at them. I'm still trying to find the cheap way to get a VLSD in my car. I'm stuck on axles.

Sounds like you might be running lean because the ECU isn't connected to the AFM. You'll have idle fuel but no fuel from the AFM vane which will raise your idle a little. When you open the throttle it goes way lean and dies. Checking the pins at the ECU might be the easiest, quickest way to confirm. The 100 and 180 ohm measurements are the important ones, for a 280Z. Pins 6, 8 and 9 I believe, it's in the FSM, just measure actual values at the ECU connector pins instead of continuity. ECU pin numbers match the AFM pin numbers.

One of the Hybridz members just had a similar situation and ended up with a damaged cage like yours. You might start a new thread with a link to this and put a good title on it. Your problem isn't from the MM product, but from the Q45 CV axles. Search Q45 CV axle and you might find somehting. Read jmortensen's Differential thread in the FAQ section and you'll find a description of what you have to do to get the Q45 or 300ZX VLSd to work. I think that, in general, they say that you have to buy four Q45 axles and mix and match parts to get two good ones. Edit - Mikelly posted at the same time. Still not clear why you seem to have the other problem, of too much clearance allowing the axle to come apart. Anyway, lots of new stuff to read.

I think that those are VLSD axles. 6 bolt 280ZX axles are 3 sets of paired holes. You probably have the shortnose R200 setup from MM. There is a link within this link that shows an install. It might give you some ideas. http://www.modern-motorsports.com/catalog/product_info.php?products_id=74&PHPSESSID=9e25b7fab3e9baf204ae3aa017e3d66f Here's the link - http://www.modern-motorsports.com/catalog/mm_gallery.php?album=2008+March+Proto+Q45+R200+Mounting+Proven+Brian+G/ It used to have text with it explaining the pictures but they're gone now. Somewhere out there is probably another web page with more details. Edit - pretty sure that you have to have custom axles made for this conversion. The Q45 or 300ZX axles are too long. Maybe someone got their measurements wrong.

What do you mean by "axle pullout is bad" and how do you know? I've only read one account of a CV axle pulling out and it only did it once because the balls came out of the cage(?) and destroyed themselves. Probably best to describe what type of axle you have, 4 bolt or 6 bolt (MM makes a conversion for both), and if you have the MM parts or are asking about them.

Thanks. Maybe .028" is the limit. I had posted in another thread about the fact that Honsowetz had said, in his "How to Modify..." book, to never go lower than .050" piston to head clearance and PMC and someone else replied back they both went about .028", but with forged components, not stock. Less stretch with forged, I assume. Anyway, it looks like you're on the edge. Good luck. Edit - Here's the post I was referring to. rsicard is the "someone else". He said .030", PMC said .028". With precise measurements and machine work mandatory for success, I would guess. http://forums.hybridz.org/topic/106806-long-rod-short-piston-combo-l28-tech-questions/?do=findComment&comment=999867

Did you just stick a straight edge on to an uncompressed gasket on the block and use a feeler gauge to measure the gap betwen the straight edge and psiton top? I think a stock gasket compresses to 1.25 mm (.049"). If so, you might recalculate to figure out what the real clearance is. Can't tell what your method was.

Looks like you have 3.54 ratio R180 and your tachometer is off. I have verified that my 1976 tach reads 200 RPM high, for example. Sites like the one below, and a quick browse through the FSMs suggest that 3.7 gears are not available in the R180. http://www.zhome.com/ZCMnL/tech/GearRatios.html On the other hand, the words/numbers "R180" and "3.7" in Google brought up some suggestions outside the Z world. Try Maxima's or non-domestic. Here's one thread - http://forums.hybridz.org/topic/105397-37-rp-for-r180-diff/

The 1976 FSM would be better to use than the "bible". It's specific to your car, whereas the "bible" is general. The Engine Fuel chapter gives a great description of how things work and how to test. www.xenons30.com/reference With the AFM disconnected, fuel should come from idle enrichment only. If it's flooding, one possibility is the TPS being stuck on "full enrichment". But OAATS makes a good point about the contact switch. Are you sure that it's running rich or assuming based on the way it sounds and what it does? It might just be running out of fuel pressure when the pump turns off.

I don't know what's going on with the links. The web address is right in a new window but it doesn't open the page. Maybe it's the forum blocking viruses. If you put this - "wiring 1976 saridout site:www.classiczcars.com" - in the Google search box, the link will come up as the third hit (unless this post knocks it down). The blue wire does go directly to the tach (the branch with the inline fuse). And the module and the ECU. Three branches from the coil negative post. Aseparate harness from the EFI harness, I believe. An ohmmeter will tell you if it's the right one. Test - http://www.classiczcars.com/forums/thread36494.html