doradox

There is a not very common thing that happens that can cause your problem. If you have a misalignment of the rotor and the caliper it will cause a spongy pedal. The rotor face and the caliper piston faces should be parallel. But say if a front spindle is slightly bent then your rotor face would not be parallel to the piston face. The caliper piston has to travel a little extra distance to make up for the misalignment and causes extra pedal travel. It is not at all common so I would certainly exhaust all other causes first though. Steve

Yes, for a given pressure more area = more force. However, for a given force pushing on the pad if you increase the surface area of pad that means LESS pressure on the pad surface. The force on the pad is generated by your foot, brake pedal leverage, hydraulic piston area ratios. Force = area*pressure A larger diameter rotor is in effect a longer lever. For the same force applied to the pads the larger diameter rotor will generate a higher braking force at the tire. The increased heat dissipation benefit, as you said, is also true because the same amount of heat is generated regardless of any of the other factors. Steve

The drag coefficient has nothing to do with pad area. It is a function of the pad and rotor material. Idealized maximum friction force is roughly (coefficient of friction)* (the force applied). Area doesn't matter. Push on the back of the pad with 10 lbs and the pad pushes on the rotor with 10 lbs regardless of area. How hard the hydraulics push the pad is a function of area though. Piston surface area is the key. If the ratio between the master cylinder piston area and caliper piston area is the same before and after the swap the pads will receive the same force for a given force applied to the brake pedal and the pedal will travel the same distance. If the ratio is changed and the caliper piston area increases then more force is applied to the pads. But you will push the pedal down further. Properly working brakes on a 240Z can lock the wheels at any speed. Therefore one could assume there is more than enough braking power available. However, if you use the brakes a lot and they begin to heat up that will no longer be true. Larger calipers and pads delay that loss from brake fade (they don't heat up as fast because they are bigger) and can continue to provide adequate stopping power for a longer time or under more extreme conditions. If you want more braking power you have several choices. Larger diameter rotors. Basically a longer lever. More force applied to the pads. (Install a bigger brake booster or fiddle with piston areas and live with a longer pedal stroke) Use brake pads with a higher coefficient of friction. This one can be dependent upon the intended use. For a track car a pad that has a high coefficient when the brakes are hot is a plus, but maybe not so desirable on the street where the brakes may be much cooler. So picking a pad designed for how you drive can be important. Push harder. Steve

I'll comment. Your very Earth centric view is clearly wrong as you would see if you looked out beyond the atmosphere of this tiny speck you call home. It is much more truthful to state that nature loves a vacuum as virtually the entire known universe is filled exactly with...nothing. At least as much as you can say that something is filled with nothing, which in itself seems a little odd. Not at all unlike this comment. Steve

70-75 mph is plenty and you'll be turning around 3500 rpm or so. No need to run in third. Here in Indiana I can run 75 all day long and the troopers will never even blink an eye. Raving around in a parking lot may draw unwanted attention unless you have chosen carefully. Might be a lot more fun though. The idea is to get the combustion chambers hot and keep them that way. Running where you needn't ever close the throttle is the easiest way to do that IMHO. As far as how long? I usually say 30 minutes is plenty but I haven't done an exhaustive scientific study so that's always just been a guess. It's worked well for me and those I've suggested it to. Since you are doing nothing more than driving your car in a perfectly normal manner longer can't hurt. Steve

In my former life I was an auto technician and owned my own shop in Tucson AZ. We would get customers, typically seniors, coming in with rough running cars asking for a tune up. I'd ask how long since the last tune and they'd reply "a year or so". I'd pull a plug and other than being coated in carbon it would look brand new. I'd then ask "how many mile have passed since the last tune"? They'd reply "2000". A years worth of one or two mile trips to the market or church or wherever. I'd make sure the choke and carb were working correctly and then tell them to go out on I10 and run at the speed limit for 20-30 minutes. They'd come back with the car running like new and as happy as could be. On a carbureted car running at a high load for an extended period is the key. Combustion chamber temps need to be elevated for an extended period to effectively, and safely I might add, clean out the carbon. Short high RPM bursts or other short term high load schemes don't work nearly as well on anything but the lightest of deposits. I've used the water and/or ATF, methods to dislodge chunks of carbon from engines that were knocking due to piston/head interference . They do work. Sometimes. And in that extreme case it's worth trying before pulling the head. I don't recommend them as regular maintenance procedures but as the last resort before tearing down an engine. Regular extended high speed (highway speeds) running is a good thing for your engine. For those that store your Z over the winter a highway blast should be the last trip you make before putting her up. You'll have the best chance of getting any water, unburned fuel, etc. that might be hiding in the nooks and crannies of your engine vaporized and sucked out through the PCV valve. Steve

Since the 1972 FSM maintenance schedule shows checking the diff and trans oil level every 3000 mile are you suggesting that the only way to properly do that is to drain, measure amount drained, add if necessary, and refill? My 72 FSM gives the proper *approximate* refill capacities. Take out the plug, stick you finger in the hole, if fluid level is at or just below the bottom of the plug hole pop the plug back in and be on your way. Manufacturing tolerances for cast parts back in the day could lead to substantial differences in the amount of lube required to reach the recommended level. Hence the *approximate* refill capacities in the FSM. Steve

Did you take care to make sure all the friction surfaces were perfectly clean? A little oil in the wrong place will cause the symptoms you describe. Steve

Got mine today. Thanks for all the hard work! Steve

81 3/4 ton 4x4 Suburban. Had been a diesel and was converted to a 454 gas engine. Had a 4.11 rear end and got 8 MPG. City and highway. It constantly broke. Cracked a head, lunched a tranny. It ran hot (230+) even with a new huge diesel radiator, new water pump, thermostat, heavy duty fan and fan clutch, hoses. Probably why the head cracked. I hated that POS but my wife loved it. One of the greatest days of my life was when we sold it and bought her a new 95 Sub. Steve

The gear oil is too thick? Could you explain how thick gear oil keeps the gears in a transmission spinning with the clutch depressed? Steve

Copyright is only forfeited if it is explicitly stated that the work is released to the public domain. Also copyright does not need to be defended. That applies to trademarks. Steve

http://www.templetons.com/brad/copymyths.html It may be older than the Berne copyright convention but it's probably still copyright. Steve

Loosen the nuts holding the master cylinder to the brake booster to allow the master cylinder to swing a little out of the way. Maybe that will allow you enough clearance to remove the air clearance. Steve

Runs on regular gas, non cross flow head, wide powerband well suited to the optional auto trans. Not exactly the mark of a purpose built performance engine. The only reason the Z is at all peppy is because of a good power to weight ratio. Relatively large engine in a small car. The L24 is just as happy at 2000 rpm as it is at 6000. It has plenty of power down low and even Granny could drive it. I certainly wouldn't call it a performance engine. Try the S20 for that. Steve

Oil turns color when contaminated and/or oxidized. Fuel system running too rich could be a cause of contamination. You mentioned your engine was "tight" when you built it. If there is too much friction your oil could be overheating and oxidizing prematurely. I'd continue changing it and pay attention to how long it take to turn dark. A synthetic oil might be a good idea as they claim to handle high oil temps better than dino oil. Steve

Ya think? Steve

I'd be interested to know what injecting air into the exhaust has to do with ignition timing. Steve

Unburned gas in the exhaust steam is given additional oxygen by the air pump to complete combustion to some extent. At the federal level emissions are measure by weight (grams/mile) so they cannot be diluted. At your local test center there is a dilution effect as they are measured as a percent or in PPM. Steve

So the question was about the air injection pump and not the exhaust gas recirculator? EGR leave on. The air pump is a low pressure pump and takes almost no HP to drive. The weight is pretty insignificant too. Don't expect to notice a performance increase as it will be very small, but as other have said there will be one. Steve

It won't help performance to take it off. Steve

Typically if 5th and reverse share the same gate they share the same shift fork. Most OD 5 speeds follow this config. There are exceptions though. Steve

Can't say I've ever seen that, but that doesn't mean it couldn't happen. Or that I didn't recognize it as such. Steve

You're right that point and electronic should, and do, look about the same. It's just electronics turning the current flow on and off instead of a mechanical switch. The lack of the cone shape (healthy oscillations) is what strikes me most but the whole thing just looks off. Anyway, life was a lot easier when one could swap a component real quick to verify a diagnosis. Steve

I agree on the rebuilt module. I have always liked the Standard brand of ignition parts and Napa's premium brand. Steve