Because the 8-valve DOHC 18R-G and its variations were produced 1973 to 1982 (about 40 to 50 years ago), I would first recommend searching through
eBay motors.
https://www.ebay.com/b/Auto-Parts-and-Vehicles/6000/bn_1865334For anyone curious about this swap, a quickly readable article is duplicated from
https://www.hemmings.com/stories/article/toyota-18r-g-twin-cam![[Linked Image]](https://celicahobby.com/forums/ubbthreads.php/ubb/download/Number/30346/filename/108392.jpg)
Toyota 18R-G Twin-camTwo liters of fury: Toyota's 140hp twin-cam revver never made it to the U.S.By Jeff Koch from February 2008 issue of Hemmings Motor News
In the U.S., Toyota's rapidly growing cheap-and-cheerful reputation didn't leave a lot of room for performance frippery. In Japan, however, where a performance movement not far removed from the American muscle car scene was happening, sporting small engines were popping up in every manufacturer's lineup. Toyota offered two twin-cam fours in the early '70s: the 1,600cc 2T-G (available in the bite-size Corolla), and the 2,000cc 18R-GU (available in Celica, Carina, Corona and Celica Camry models). Pictured here, the 18R-GU, is the one that we will discuss, although neither version was available in the U.S., making this an overseas-only delicacy. Yet in their day, they were the world's best-selling twin-cam fours anywhere.
The R-series engine actually predates Toyota's appearance in America: It started in 1953, and half a decade later, it was in the first Crowns that came to this country. The 18R had grown to two liters (1,968cc) with an 88.5mm (3.48-inch) bore and 80mm (3.150-inch) stroke, putting out roughly 100hp depending on application; it came standard in some U.S.-spec Celica models. The later 18R-C adds California emissions equipment. This engine shares a bottom end, making pistons and other bottom-end parts easy enough to source.
But the 18R-G seen here, introduced in 1972 with 9.7:1 compression ratio and lacking smog controls, and unknown to all but the keenest early Celica enthusiasts, was the hot one. That G suffix indicates a two-valve twin-cam cylinder head, with power outputs up to 140hp (sometimes reported as 145hp) that, depending on your engine, could be built by either Toyota or Yamaha. Yamaha's work on the 18R-G was based on the work they'd done for Toyota previously, on the legendary 2000GT sports car.
Air injection for improved emissions created the 18R-GR in 1973, which dropped compression half a point and was rated at 130hp. The 1975 18R-GRU, saddled with a Japan-spec emissions system and a Yamaha head, was rated at 130, while the 18R-GU, adding non-rebuildable carburetors and electronic ignition, was rated at just 120hp. A fuel-injected 18R-GEU version was produced from 1978 through 1982, and was rated at 120 horsepower despite a further compression drop to 8.7:1. Competition variants of these engines powered Celicas competing in world rally events in the '70s; the most extreme of these had four-valve cylinder heads and made up to 240hp.
Prepped 18R-G Celicas were said to outrun the feared 240Z and Skyline models that were its contemporaries, while Levins and Truenos (sold as Corollas in the States) took on and beat comparable twin-cam engines from Alfa Romeo, Ford/Cosworth (Escort), Ford/Lotus (Cortina), and Lancia. Apparently, some European Formula racers went to the trouble of making their own cam covers to help disguise their engines' Japanese origins. Any pre-emissions head is regarded as the best starting point for any and all modifications: It has the best cams, the best airflow characteristics, and responds well to porting, polishing and other tuning tricks.
Our feature-car is an RHD Japan-spec 1977 Celica, owned by Koji Yamaguchi of Hawaiian Gardens, California; the car debuted this past October at his annual Japanese Classic Car Show in Long Beach, California. Its engine is an 18R-GU, and features a non-stock handbuilt exhaust header. We took it for a spin; though redline was at an indicated 7,000 rpm on the tach, we shifted at 6,000 rpm as a courtesy. While we found that the power was linear, with more to be had higher up in the revs, we were also amazed that even in fifth (an overdrive gear), we didn't need to shift down to go deeper in the revs to keep the power up. The cabin, meanwhile, filled with a sweet mechanical chatter that has as much personality as any European twin-cam.
Koji reports that swapping an 18R-G engine into an early Celica is a snap, as they use all the same mounts. They also hook up to the W-series transmissions. But the 18R-G head will not bolt onto a 20R/22R Celica block.
Additional Reading:https://en.wikipedia.org/wiki/Toyota_R_engine#18R-G
