Rebuilding a Lotus Twin Cam Engine | Restoration Impossible Lotus Elan Project Car Part 3

Buy the best example you can afford.”

It’s car shopping advice we seem to have shared a million times—maybe more. Like the cobbler with the barefoot kids, however, we are often the last to do for ourselves what we know best. 

That’s our only explanation for why we found ourselves in a Michigan field buying a destroyed Lotus Elan.

How bad was it? After a wreck that likely totaled it, this Lotus spent the next four decades—every spring, summer, fall and winter–just sitting, uncovered, in that field. But where others saw only damage, we saw a challenge: Could we not only save this one, but also make it nice enough for Amelia Island? So we dumped everything into a little cargo trailer and dragged it home. 

There was one bright spot in this giant mess: Before the car was put out to pasture, the Elan’s jewel of a Twin Cam engine was removed and stored inside. 

It’s time to turn our attention to that engine, along with the transmission. And while we did our own work in disassembling the body and chassis as well as prepping them for blasting, we decided to call in outside help for this stage. We do build engines here at the shop, but the Twin Cam’s specialized nature made this seem like the best option.

There are several Lotus Twin Cam experts in the U.S., and we are blessed to have two of the best right here in the Southeast: Georgia’s Savannah Race Engineering and Florida’s Twin Cam Sportscars. 

A strong recommendation sent us to Twin Cam Sportscars, which is located in Sarasota. There we met owner Steve Smith and got a tour of his neat and tidy shop. After years spent working on vintage race cars back home in England and here in the States, Steve opened his own shop in 1992. While he maintains and does light restoration work on all British cars (and personally races a Ginetta), Steve started specializing some years ago in the Lotus Twin Cam engine.

Yeah, this would be the right shop.

What We Found

We were told when we bought the car that the engine had been recently rebuilt, but the grease and dirt all over the engine made us question that statement. After pressure washing the engine and opening it up, we got a pleasant surprise: It had, indeed, been rebuilt. Not only that, but the head also featured a few upgrades, like hotter, SE-spec cams and bigger Sprint valves. Those cams, by the way, looked to be in good condition. Reusing them would save us some money, especially since we had already planned to build the engine to those later, more powerful Sprint specs. We also discovered that the engine was still at standard bore, while the original crank was also in good shape. 

Not all was perfect in engine-land. The previous builder had retained the original, smaller connecting rods; these days, most Lotus engine builders opt for the later, larger rods–which are simply known as “big” rods in Lotus circles. Someone had also incorrectly line-bored the engine block, so the crank did not fit properly. And the torque specs were all over the place. Despite those concerns, Steve still said this would be a relatively quick and easy rebuild. 

What We Built

Our plan was to keep the engine concours-correct—at least visually—while incorporating a few internal upgrades. We also made it clear that we weren't willing to sacrifice reliability or drivability. 

Steve says it takes about 40 hours to assemble one of these engines. Then budget a grand or two for machine work and parts. Total expected cost: $8000 to $10,000. For that money we wanted to end up with something that was smooth, powerful and reliable enough to tackle some rallies and tours once we’d shown it off at a concours event or two. 

Steve understood what we were looking for and knew exactly what to build. He would give us that big-valve power with a few tricks added in. He said to expect about 125 horsepower without any reliability, drivability or overheating issues.

Step 1: As purchased, the block sported bright-yellow paint and the valve cover was black, though neither color is original. A Series 1 Lotus Twin Cam engine would have had a gray block with a silver-blue valve cover.

Step 2: Once we opened up our Elan’s engine, we found more good news than bad. The camshafts were CPL-2 competition spec, so we knew they came from a later Elan SE. The “CPL” stands for Cosworth Production Lotus, while the “2” denotes a competition grind. Competition cams have gotten more radical in recent years, though, so these later Sprint cams are now considered hot street pieces—perfect for our needs. 

Step 3: A micrometer confirmed both cam spec and condition.

Step 4: After pulling the valve cover and inspecting the cams, we removed all of the other ancillaries. The distributor looked good, but we decided to send it to Advanced Distributors for a rebuild. Even the early-style fuel pump was present, although it would also need a rebuild.

Step 5: More good news: The engine still had its original cylinder head. These early Weber heads have the intake manifold cast into the head and cost thousands to replace. Although a good machinist can convert a later Stromberg head to the Weber style by cutting off the original manifold, drilling the head, and welding on the necessary flanges, it’s a lot of work.

Step 6: At some point our head had been fitted with larger Sprint valves, too.

Step7: Even though those valves appeared to be in good condition, we opted to replace them with new pieces sourced from Lotus parts house R.D. Enterprises. A visit to its renovated, nearly 300-year-old barn in northeastern Pennsylvania is worth the trip, and owner Ray Psulkowski and his team had everything we needed. We also planned to deck the head from the stock 4.64-inch thickness to 4.5 inches to replicate the high-compression engine found in the later Elan Sprint. We targeted a compression of about 9.5:1.

Step 8: Steve could now measure the cylinder bores. Thankfully, they were still stock. We’ll overbore them by 0.010 inch to smooth out any scratches.

Step 9: When it comes to the Lotus Twin Cam, street cars commonly use one of two styles of connecting rods: either early (left) or late (right). The larger, later rods (marked “125E”) are stronger and therefore the best choice when rebuilding a nearly stock Twin Cam. Our engine still had the early rods, but Steve had a good set of the later ones that we used.

Step 10: We paired those later rods with forged JE pistons. Forged pistons typically aren’t needed in a street engine that will turn less than 7000 rpm, but cast pistons are no longer available. Our pistons have also been notched to clear our oversized valves.

Step 11: Steve likes to reuse the stock main bearing bolts, believing that the bearing caps will fail long before these Ford pieces. All other hardware, such as the rod bolts, came from ARP.

Step 12: Steve rotated the engine every step of the way to make sure he hadn’t picked up any friction. During the rebuild process, he also had our crank polished and balanced.

Step 13: Cam timing is set with a degree wheel at the back of the engine and a dial indicator on top of the head. This step is critical to creating a properly running engine.

Step 14: Gustafson Specialty Products, famous for gear-reduction starters, has just prototyped an alternator conversion that fits inside an original Lucas generator case. This conversion solves the early Lucas generator’s notorious habit of not providing a high enough charging rate—only about 22-24 amps. The upgraded setup can deliver 55 amps, looks concours-correct, and installs easily. British Wiring supplied us with an Elan wiring harness that had already been modified to run an alternator.

Step 15: Fortunately our engine came with its original Weber 40 DCOE 18 carburetors, which are rare, expensive and original to the early Lotus Elan. While any Weber 40 DCOE would work, concours standards demand that ours carry the “18” designation. The crew at Pierce Manifolds said they could rebuild our derelict carbs to like-new condition.

Step 16: As promised, Pierce Manifolds resurrected our Elan’s basket-case Webers. They vapor-honed and then ultrasonically cleaned the bodies before replacing the throttle shafts and all the hardware and jets to restore our carburetors. Expect to pay about $600 per carburetor for this service; we considered it money well spent, since these units are worth upward of $2000. Since we’ve changed the engine specs, we might need to rejet our carburetors, but we’ll wait until the car is on the dyno.

Step 17: Time to button up the long block and bolt on the valve cover, which will come back off once it’s home in our shop for a coat of the correct silver-blue paint. Steve tells us that it takes about 40 man-hours to build one of these engines, but our build was spread over a couple of months to allow time to order parts and send pieces out for machine work. We found Steve and his crew to be fair, honest and very knowledgeable.

Step 18: As the rest of the Elan comes together, the engine will wait patiently in the shop. We just need to source the correct plug wires for concours events.

Step 19: Steve also went through our gearbox, which was the original close-ratio Ford unit that was correct for our Elan. He found that the front and rear main shaft bearings were bad, as were the tail shaft and input shaft seals. He also ended up changing the excessively worn layshaft and replacing its needle bearings. After a good cleaning and a coat of concours-correct gray paint, the assembled transmission was deemed worthy of many more years of use.

5 Things to Know About Lotus Twin Cams

  1. With a properly built engine and steel crank, you can safely spin one of these engines to 10,000 rpm.
  2. The water pump is not an inherently bad design, but it fails because careless owners and mechanics tighten the belt too much.
  3. The water pump rebuild kits available today include an improved bearing to lessen the chance of pump failure.
  4. If you seal the timing cover with silicone, you risk blocking the oil squirter hole that lubricates the timing chain.
  5. If you put a 1/8-inch restrictor plug into the left-front top of the block, the cylinder head won't be flooded with oil. The result of this mod: increased engine life.
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