Tech Tips: Datsun 240Z

The 240Z was a landmark vehicle when it was new. The styling was a real break for a Japanese manufacturer, and there were so many details that they got right: independent rear suspension, overhead cam engine, light weight, right price. It had everything going for it.

Buying and Ownership

The thing you want to watch for on all of them is rust. The spot most people aren’t aware of is the cowl panel area. There’s a foam pad that the factory installed under the cowl panel, either for heat insulation or sound deadening. It retains a lot of moisture and the cowl rots from the inside out. Other rust-prone areas are in front of rear wheels and the horizontal area where the hatch closes. The engines are virtually bulletproof. We’ve taken heads off of engines with almost 200,000 miles, and you can still see factory hone marks on cylinder walls. The blocks are very sturdy, and so are the crankshafts. The 1970-’71 cars have the A-series gearbox, which tends to be more fragile than the B-series gearbox. Listen for whining noises from the differential gear carrier. It’s rare to have a problem with the original gearset. Generally, if they’re set up from factory, you never have to touch them other than to change the fluid. Getting that tooth-pattern interface is critical if you change rear-end gears from the stock 3.36. If you don’t get it right, they whine like a ghost. Anyone who’s changed a camshaft in these cars understands that the rocker geometry is extremely important. You need to change lash pads to keep proper geometry–you don’t just adjust it like in any Chevy or Ford. The lash pads are in the valve spring retainers. What you’re trying to do is ensure the lobe of the camshaft is contacting the center of the rocker arm. If you don’t get it right, it will chew up the cam in just a few hundred miles. In 1970-’72 and some ’73 cars, there’s a large red-and-white power wire that feeds into bottom of the fuse box. It will sometimes cause the fuse box to overheat and melt. I’ve never seen a fire caused by this, so it’s not a big safety issue–but it is something to keep track of. If you see distortion or melting in the bottom of the fuse box, replace the fuse box immediately. The hardest parts to find right now are probably things like front fenders and hoods. The good news is there are a lot of parts cars out there. Those types of parts are not prone to a lot of rust, so if there’s collision damage, it’s not hard to find used replacements. All other mechanical and interior parts are being reproduced, and more and more come out on the market every year. If you have a ’73 or ’74, see which carburetor is on the car. They came with a Hitachi, which looks like an SU but is not the same as on earlier cars. It’s built for emissions compliance. Swapping to an SU will improve performance. Popular upgrades–exhaust, headers and a hot camshaft–yield a real good return. With the SU-type carburetors, changing the mixture is a simple job. A word of caution, though: Everything needs to work together and in balance. One of the first things people did years ago is put triple Webers on them. A lot of folks were disappointed if that was the only modification they made: It increased the ability to take in air and fuel, but did nothing to take it out. Likewise, a camshaft with the stock exhaust won’t show the full benefit. If you do headers, exhaust, camshaft, and a carb tune, you’d be close to 200 horsepower depending on the grind of the cam and the condition of the engine. There’s a lot you can do with the suspension. There are all sorts of bushing upgrades, anti-roll bar packages, strut bars and so on–lots to drastically improve the handling. You still see plenty of Z-cars doing all kinds of autocross and vintage racing because they do so well. Most people tend to do springs first, but the two biggest changes you can make are shocks and tires. We sell a variety of lowering springs–and they do work–but if you just put in lowering springs without adding a good-quality performance shock or making sure you have a decent set of tires, you won’t see as much improvement as if you had a balanced program. The sweet spot for the 240Z is the 1972 for a lot of reasons. Its B-series transmission is stronger. The wheelbase is slightly longer thanks to a relocated differential, which improves the ride over earlier vehicles. It also has a more powerful alternator. That said, I wouldn’t shy away from a ’70 or ’71 if it were in good shape. The ’73s are also really good cars if you change the carburetors, and they have a few electrical upgrades, too. Any one of those four years in great shape is a worthwhile investment: Their values are only increasing. There are no more $250 parts cars out here on the West Coast. Even the stuff that’s rough and in need of restoration has increased dramatically in value over the last few years. The 240Z isn’t in the same value range as American muscle or old Porsches, but it is a milestone design. It’s the first Japanese volume sports car that really stood on its own. That makes it a very significant vehicle. The cars that seem to get ignored are the 280Z and even the 260Z. There were a lot of improvements in the later cars. You can do all the same upgrades as you can to a 240Z, but the cars themselves are often half the price. They’re a lot of fun and will perform well. Collectors and enthusiasts often shy away because they don’t know how to work on the fuel injection. The Bosch L-Jetronic system is not that hard to keep in tune, and it runs great. Remember not to chase the problem by exchanging parts, but by doing the proper testing like the factory manual recommends. Back in the ’70s and early ’80s, these systems were a mystery to most people. As a result, those cars didn’t get the respect they deserve.

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4/4/19 8:06 p.m.

a few separate paragraphs would make this article a bit less...breathless?


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