jmortensen

The problem is that people believe what they want to believe. Once the belief in something sets in it's very very hard to get accurate measurements out of someone.

Thanks for the discussion guys. I've had this problem as have a bunch of my friends with Mikunis. I messed around with my float level quite a bit to fix, but this seems like it's so easy to do that I'm definitely going to do this mod as well.

If you get rid of the open diff and get an LSD that is not the Nissan 2 pinion LSD then the R180 is fine. I know 2 people who had the 2 pinion Nissan LSD, both broke it, and I bought the R200 for just that reason, not knowing at the time that there is also a much stronger 4 pinion LSD available. The Quaifes or Torsens are very much overpriced, and that also factored into why I went with the R200. I used to sell diff parts and we had a stack of Zexel Torsens for Camaros that were $135 and they sat on the shelf for YEARS. Nobody wanted them. For "new stock" we had Dana TracLocks (another very similar design) for $350 to $500 depending on the size for just about every American car out there. For some reason when you try and get the same type of diff for a Datsun a "good deal" is $1200. IMHO, a big ripoff. I looked up Haldex as I had never heard of that type of LSD before. Looks like its more designed to transfer torque to the rear for an AWD car than as an LSD inside a diff. Even if this were available for an R180 or R200 I'd still go with one of the others. Just MHO. Some more info on that one: http://www.haldex-traction.com/technical_information/design_info/actual_design.htm#

Actually pulling the carrier out of a diff is very easy. As long as you keep the shims straight it goes back in easy too. Getting the diff in and out of the car is the hard part, but I guess I assumed you had one already out of the car. The hard part of setting up gears is setting the pinion depth, but in order to take the ring gear out removing the pinion and it's associated shims is totally unneccessary. But that's a moot point since you apparently know the history of the gears. So the answer to your question is that the 5mm smaller ID makes no practical difference as far as the strength of the gears and all that, so there is no reason to avoid or prefer one over the other.

The ID of the ring gear changed sometime in the mid 70s. Most of the aftermarket LSD's are 115 mm, so if you have the 110 they are too large to fit into the smaller ring gear. BTW its ring and pinion, or crown and pinion, not rack and pinion. I suppose on your 3.90 you'll have to pull the ring gear off and measure the ID to know what size it is. 3.90, 4.11, and 4.38's are all common ratios from the front of 80's Nissan 4x4 trucks here in the US. I don't believe any US version Z car ever came equipped with a 3.90 R180. So if you were in the US I would doubt that it is the 110, unless some early owner of the car went and bought 3.90 gears from Nissan Comp. Europe was probably different. You got 5 speeds, so it would make sense that you got lower diff ratios as well.

I don't think you're going to get much cleaning action out of 2 oz of Acetone in 10 gallons of gas either. Just pure BS.

Uh... I'm gonna go ahead and call BS on that one. I have run other types of solvents/paint thinners in my gas. I've used Tolulene and Xylene in much heavier concentrations of 5:1 with gas and I can tell you that those increase your octane but not your mileage.

You know you're right. I think I misread his original post. I thought he was saying that his pedal went most of the way to the floor with no brake engagement. The typical master cylinder test is to step on the brakes with a light pressure. Usually a bad master will let the pedal slowly fall to the floor. Then if you hit the brakes really hard the pedal will hold the pressure. Try that and see what happens. If oil=brake fluid then he obviously has another problem of the fluid leaving the system somewhere. Could be the master leaking into the booster or one of the connections in the hard lines or a bad caliper or wheel cylinder.

510s have R160s. They are lighter than R180s and use the same halfshafts and everything. I see no reason why the PO didn't tell you the truth.

The 260 cam has a tiny bit more duration. Mild improvement is an understatement. There is no point IMO in swapping cams for this 10º or whatever it is more duration. Get an aftermarket cam if you want a cam. At least you'll be able to tell the difference after all that work is done. Jason is right about the cam towers. Swapping the towers is not hard at all though, so if you really wanted to do it you could. I know it's not the "right" way to do it but I swapped a cam and towers on an engine without pulling the head. I did drain the coolant and pulled the spark plugs, but I then pulled the towers and swapped them over. Ran that engine in autoxes every month and on the track a number of times in addition to my daily driver miles. It had something like 40K on it when the front crank pulley came apart and that engine came out. My point is that if you're careful you can swap the cam without changing the headgasket.

Search for "reaction disk" if you want the long version. Short version is it sounds like you dropped a little rubber disk into the booster when you were swapping the masters. You need to pull the master and look in the bottom of the booster, fish that puppy out and stick it in the center where the pin for the master cylinder goes.

Wow, I wasn't even aware that head existed. Sounds like a good one to start with.

I think it is worth it. Here is a good related thread with nice pics of what should be done to the chamber, although this head still has the smaller seats in it: http://www.classiczcars.com/forums/showthread.php?t=13114&page=1&pp=15&highlight=E88 If you haven't already seen it, it is possible to get a P90 which has a better combustion chamber shape and shave it .080" to get compression. Then you shim the cam towers up .080 to restore the cam geometry, and use the longer N42 or N47 valves in it. If you're looking for a head to use with pump gas, that's the way to go IMHO. The machine work is quite a bit less expensive than installing new seats in the E31 head. There's a guy with all the info on his site, I think it's called the Datsun Garage, but I can't find the link right now. If I had it to do over again I would have sold my E31 to someone who wanted the original head and done the P90 instead...

Interesting. I was pretty sure that was going to be a good answer...

I use Permatex Ultra Grey. On exhaust manifold gaskets I use the Ultra Copper. Both work fine.

Not to thread jack, but what ended up happening with that transmission gira was trying to get fixed for the race?

Hmm. Learn something new every day...

Yep. One thing you can do is cut the front of the oil pan gasket off. Use silicone there instead. Again, biggest risk is that you might get a leak in the corners.

True. You don't need to take the head off. I always put my headgaskets on dry. I have a nasty tendency to get a little leak around the corners of the cover where the cover meets the head gasket and oil pan gasket. Put a dab of silicone in those corners that is big enough to seal after the cover gets in place. I think my problem is I don't put enough on and it doesn't smush enough to seal. Then you have to take the cover back off to get the damn thing sealed, and that is a PITA. Also you should loosen the top bolt for the curved chain guide to help get the sprocket on the cam. Once it's on then you can move the guide to where it needs to be and tighten it down.

Nobody else caught the fact that you CAN'T lock the door with it open?

If you just stick a P90 on a flat top block you end up with 8.3:1 or 8.5:1 compression. Not exactly high enough for a hipo NA build.

I pretty much agree with zguitar. My L28/E31 setup requires 95 octane, but runs strong at 11:1 compression. If I had it to do over again I would have started with a shaved P90 and saved myself the hassle and $$$ of having to install the larger valves in the E31. I also spent many hours cleaning up the combustion chamber where a P90 would have required maybe 1/4 the time to get a better result in the end. The nice thing about the N's is that you slap them on a flat top block and you've got a good compression ratio for a NA buildup. They really aren't the equivalent of the P as far as the chambers go though. They have been the head to have for a long time because of the ease of installation and the lack of modification to get a decent compression ratio, but for someone willing to spend a few bucks the modified P is the way to go. If you're really going all out then it doesn't really matter which head you start with, because you'll inevitably end up with something like this: http://forums.hybridz.org/showthread.php?t=104420 check post #12. In the US the P90a was a hydraulic head, but some heads have been coming from Japanese importers that are marked P90a but have lash adjusters and not hydraulic lifters.

I don't think so. Bumpsteer isn't about the rack getting lower or higher in relation to the ground as the suspension moves through the travel. It's about getting the angle of the control arm equal to the angle of the tie rod. Lowering the rack the right amount will make the bumpsteer better. Think about it this way: if you raise the control arm pivot you can make the bumpsteer better. So that means that the control arm pivot is too low in comparison to the inner tie rod. So options are to lower the rack or raise the pivot. This graphic from Rob might make it clearer. I know it helped me when I managed to confuse myself... http://forums.hybridz.org/attachment.php?attachmentid=155 The downside to lowering the rack is that you can't later raise the control arm pivot. A closely related issue to bumpsteer (on a Z anyway) is roll center. The roll center is such that when you lower the car more than a couple inches it gets too low and actually goes below ground. A roll center below ground increases body roll. You can mitigate that issue with "bumpsteer spacers" which are really "roll center raisers". One issue with bumpsteer spacers is clearance for the wheel. You can't just keep adding bigger spacers because of tie rod to wheel clearance issues, which is why you can buy different heights of bumpsteer spacers for 14 and 15 inch wheels. So everything will be fine in your BMWZ if you leave it near stock ride height. You can choose to lower the rack and actually improve the bumpsteer in doing so if you lower it the correct amount. You'd need to measure the bumpsteer while you lowered the rack to get it exactly right. Or you could conceivably use the JTR method and just lower it 3/4" and it should be in the ballpark. If you decide you want to lower the car a lot you may run into issues with the roll center, which means stiffer springs to control the body roll and the $$$ struts to handle the spring rates if you're feeling racey. If you haven't already looked, it's not going to be real easy to move the rack. If your plan is to lower the car 1" and drive it on the street, I'd say don't mess with the bumpsteer at all, and cut the oil pan to gain clearance at the crossmember, especially if you're not going to race the car.

Lowering the rack also changes bumpsteer. Could be used to fix bumpsteer in a Z if lowered the right amount since the rack is too high relative to the control arm pivots in the stock location, but could also really screw it up, and you'd really need to measure to get it right. I agree with you that moving the engine back is the way to go if you can. I wouldn't be too worried about cutting into the oilpan if that ends up being the easiest solution. Look at how shallow it is at it's most shallow point. You can go that depth all the way across if you have a dry sump. The only reason for the sump is that it is a sump and it stores the extra oil. If you had to really modify it and lost a whole lot of capacity you could add "wings" to it like a Nissan Comp oil pan to get back the capacity.

My advice is even if you bore the block you should notch the block anyway. If the valve just barely clears then you won't get any flow around that side of the valve, not to mention the valves might get closer than you think when they're flopping around at 7000 rpm. General idea is to lay the headgasket on the block and mark where the fire ring sits (scratch it with a pick). Then take a die grinder with a burr and grind away the block up to the fire ring line. According to How to Modify you can go to about .040 above where the top ring stops. You might also want to do the same thing on the head. Not sure how the head will line up with the 280 chambers, but if you can remove any "extra" alumimum on the head around the valves it will help. Your valves are going to be so close to the cylinder walls that it's a good idea to get every little bit you can.