74_5.0L_Z

A little while back I weighed my 5.0L ford powered 260Z at the drag strip. With 16 gallons of fuel, fifty pounds of tools in the passenger floor, and my daughters baby seat, the car weighed 2675 w/o me. I have since put the car on a little diet. The front bumber and mounts were removed, etc... So, curious about weight distribution, I did the following to get a rough estimate of weight distribution. 1. I measured the length of the springs with the car on level ground and the suspenion settled from a short drive. Front springs 8.5 in compressed Rear springs 6.5 in compressed 2. I subtracted the compressed height from the free length of the springs. Front Free Length = 12 in (200 lb/in) Rear Free Length = 10 in (175 lb/in) therefore each of the springs was compressed 3.5 in. Knowing the spring rate of the springs, I then calculated the force being applied along the spring axis. Rear 3.5 in * 200 lb/in = 700 lb Front 3.5 in * 175 lb/in = 612.5 lb Then using the angle of the struts and some trig, I calculated the force perpendicular to the road surface. 700 lb / cos(13.5) = 680.7 lbs /rear wheel 612.5 / cos(13.5) = 595.6 lbs / front tire As a reality check, I summed the four tires 2* 680.7 + 2* 595.6 = 2552 lbs This is what I would have expected because the car had only 12 gallons of gas and no tools, baby seat, or front bumper. This yields the following weight distribution. 46.67 % on front 53.33 % on rear I view these results with some skepticism because of inaccuracies in spring rate, etc..., but I find them encouraging. Dan McGrath

The Zs come from the factory toe-in. If you lower them they get more toe-in. The adjustable camber bushing that are available through G-machine and other can be used to adjust the rear toe. I recently installed them in mine, and I'm pretty happy so far.

What I was referring to gives ball-park toe settings that are safe until the car is properly aligned at a shop. Here is what I do. 1. jack up rear of car. 2. hold a piece of chalk stationary below each tire and rotate the tires to get a line around the circumference of each that is in plane with the tire's axis of rotation. 3. Lower the car and settle the suspension (carefully drive or push the car so that the rear suspension is in normal driving position). 4. In front of the rear tires, measure between the lines marked on the tires as high up on the tire as the body will allow. 5. In the back of the rear tires, measure between the lines marked on the tires at the same height as front of tire measurement. 6. Subtract front measurement from rear measurement. If difference is positive(front measurement is smaller) then your rear tires are toe-in. A small amount of rear toe-in is desirable. This method does not measure true toe-in because you are not measuring along wheel axis. This methof gives a qualitative(am I toe-in or toe out) answer. To determine whether the tire are aligned with the length of the car more needs to be done. For further, elaboration on suspension set-up refer to Fred Puhn's book "How to make your car handle"

I don't know if you've driven the car yet. But, I would make double sure that the rear tires are not toed out. Toe out in the rear causes a very unstable condition(the rear end will come around easily and without notice). Measure between lines drawn on tires with the car in its normal driving position. Verify that you have either a slight toe-in or zero toe in the rear. Dan McGrath

I have a friend with a complete set of the old centerlines new in box for a Z car. He started a Z project ten years ago and never finished it. They are 15 x 8 with 4" of backspacing. I know he would sell them at a reasonable price. Dan

Backspacing and offset refer to the same thing but are measured differently. Backspacing is the distance from the inside edge of the tire bead to the mating face of the wheel. Offset is the distance of the mating face from the centerline of the wheel. For example, I have 15x8 in wheels (measured from inside of tire bead to inside of tire bead) each tire bead extends an additional 1/2 inch. Therfore my 15x8 wheel actually measures 15x9 from the outside of one bead to the outside of the other. My backspacing is 5 inches. Thus measuring 5 inches from the outside of the inner bead I place my mating face 1/2" outside of the center of the wheel. These wheels have a 1/2" offset. With stock springs, you are limited to about 3 5/16" of backspacing regarless of width. This backspacing assures clearance with spring. The width will be limited by fender clearance. Good Luck, Dan McGrath

I have 15x8 in Centerline Billet Scorpions (style 91)on my 1974 5.0L powered Z. They look great IMHO, and are light. I have been Autocrossing the car with no apparent problems with the wheels. They use the stock bolt pattern, and have a 5" backspacing. I have 245/50/15 Dunlop SP8000 mounted on them. The tires fit inside the wheel well. You need coil-overs to use 5" of backspacing.

I have a 5L and T-5 in my 1974 260. I use 245/50/15 tires(24.7 in tall), and a 3.545:1 rear gear. The car is really streetable, and does well at the track. In normal daily driving, I don't use first gear (too easy to spin the tires). I use second through fifth. On the highway, 70mph is 2300 rpms. I tried a 3.70 gear and changed it after only two weeks. I like the 3.545 gear much better. I wish I had a 3.36 gear.

All 260Zs came with R180 differentials. The coupes have 3.36 to 1 gear ratios, and I think the 2+2 models had 3.70 to 1 gears. The 240/260 is easily upgraded to the R200. The easy way to identify an R180 versus an R200 is to look where the axle enters the differential. If the axle enters the side of the differential case through a bolt-on flange then it is an R180.

On pump gas with iron heads you are limited to about 9.5:1, if you go to an aluminum head you can run about 10.5:1. The higher your compression ratio, the higher the combustion chamber pressure will be. If the combustion chamber temperature reaches a critical temperature before the spark is introduced, you will get early combustion. A flame front will be started by compression then another initiated by spark. The colliding flame fronts cause knock, and huge pressure spikes. The result is broken engine parts. This is somewhat of an over-simplification. Your actual maximum compression is affected by the cam profile. If you run a cam with a lot of overlap, then you can use more static compression. For a motor that will live on the street I'd sick with the limits given earlier. Thanks, Dan

I like some of what I saw on the CobraZ site. Some other things I dislike. What I like: 1. I like the simplicity of their mounts. Mine are more complicated. What I dislike: 1. The engine is too far forward. About 2" further forward of mine. It looks like the reason for this was the factory shorty headers. 2. The engine is too high and at too much of an angle. Again I think this was too allow use of the factory headers. The datsun differential is mounted at approximately 5 degrees nose up, so the engine should be the same. From the photos on the site the angle looks greater. My engine is mounted at 2.5 degrees nose up, and the tail differential has been raised to match. The high mounting position of the CobraZ and the large angle will prevent use of the factory 5.0 clutch fan. 3. The CobraZ will need to run a remote oil filter. 4. The cobraZ will need a hood scoop, and/or a tiny air cleaner. 5. The T-5 shifter will not be aligned with the shifter holes in the floor or console. One more thing Cobra engine have factory roller rockers; the engine shown on that site does not.

I have found an R200 LSD from a 1988 300ZX. It is the clutch type. I have some questions. Can I use the half-shafts from an earlier R200(That's what is in the car now)? It it as simple as popping out the 300Z half-shafts and popping in the 280Z half-shafts. Can I use the early style rear differential cover? I know that there is a special brace available that clears the finned cover, but I don't want to buy it immediately. What is the break-away torque of the 300ZX units? Thanks, Dan McGrath

My 1974 260Z with a stock 5.0L / T5 has run a 13.21 @ 103.6 mph on street tires. With drag radials, the car would easily be in the 12's.

I get the following codes: 67, 81, 82, 85 These codes are generated because I don't have the air pump solenoids (AM1, AM2), the canister purge, or the VSS connected. These are Key On Engine Off codes. I haven't been able to retrieve any Engine running codes. This might be because I don't have a clutch engine switch connected.

The speed sensor on the T-5 is used for two things. First, the computer uses it to determine whether you are idling at a light or coasting. The computer has different fuel, spark, and EGR modes for idling at rest or coasting. The other use is for cruise control. The tachometer should be triggered SPOUT connection coming from the distributor (the SPOUT connector is electically equivalent to the negative side of the coil). You can pick up the connection at the driver's side firewall connector.

Here are some numbers to put things in perspective. If you have 24.7 in tall tires (245/50/15), 3.545 gears, T-5 transmission. 6200 rpms in 5th gear is 189 mph. If I were you, I wouldn't worry too much about getting gears taller than 3.36 or about fitting tall tires. The limiting factor on your top speed will be horsepower and drag coefficient, not gear.

The speed for a given distance from the center of the rotor is given by s = R * w where w is the angular velocity of the wheel in radians, R is the radius from the center of the rotor, and s is the linear distance. Therefore the larger the rotor, the higher the relative speed between the rotor and pad.

I am using copper header gaskets on my 5.0L ford engine. Before I installed them I went through 3 sets of gasket in 2 months. I've had the copper gaskets in for nearly a year with no leaks and no problems. They have a raised crush area around the port. They are a liitle more expensive but can be reused.

This probably doesn't help you very much, but the Ford EEC-IV engine management system uses a relay (WAC Wide-Open Throttle AC Cutt-off) that kills the power to the compressor for 10 seconds during full throttle operation.

I don't mean to dampen the excitement about these kits, but you cannot use the 5.0 mustang shorties without puuting the engine too far forward. The T5 shifter will not come out of the factory shifter hole in the body or console. I tried. With the engine as for back (header flange against the fire wall, and engine as low as I dared) the shifter was too far forward. I ended up using block-hugger headers, and slid the engine 2 inches further back. The rubber mount on the tranny is 4" behind the factory transmission body mount.

I have the 3.545:1 ratio in my 5.0 / T5 powered Z. I really like this combination with 24.7 in tall rear tires. I had 3.7 gears in the car when I first put it on the road. I changed them after 2 weeks of driving. I would like to try 3.36 gears but R200s with that ratio are hard to find. Currently, 75 miles/Hr in fifth gear is 2700 rpms. The car is a pleasure to drive.

I have built several carbureted 302. My experience says don't over-carb. I was most happy with Holley 600 double-pumper. I later tried a 750 and a 700. The engine was much more crisp with the 600 DP. So, If it me, I'd go with a 600 or 650.

The reason that I chose to build a V8 zcar was the ease with which a high horsepower to weight ratio can be achieved. It is not necessary to build an engine that is on the verge of self-destruction in order to have a very fast car. I have a bone stock 5.0L mustang engine in my car. The car has been a daily driver for nearly a year, has seen ~ 40 passes on the drag strip. I intend to auto-X the car this weekend. Although the car is not as fast as some of the more modified cars on this site, my Z is faster than most vettes, WS6 Trans Ams, etc... The car gets ~20mpg, and I have had no reliabilty problems.

The Neapco part number of the adapter is 2-2-899-1

I just finished mounting 1985 maxima front rotors and Outlaw 2800 series (1.38" piston) calipers on the rear of mine. They work great. I had to have custom plates made to mount the caliper. Here is a break-down of the costs: calipers (2) * 125.00 = 250.00 Mike(scca) rotors (2) * 25.00 = 50.00 napa brackets (2) * 60.00 = 120.00 custom hoses, misc. 50.00 afco pads 1 set 60.00 Mike scca This may seem excessive but was well worth it. Before the mod, the rears were worthless. Now the rears are extremely effective.