A once-dormant Lotus project gets off the ground floor

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I finally took my own advice to get my Lotus Europa project back on track. Last week I described my method of doing one thing a night to restart the long-dormant project, as well as how I finally got the block and other lower-end parts back from the machine shop, allowing me to complete my milestone of setting the block on the engine stand. After removing and tearing the engine down nearly five years ago, the engine assembly began in earnest.

First, let me say that I am by no stretch of the imagination an engine builder. This is perhaps the sixth engine I’ve assembled, and that’s really all I do—assemble. I rely on a machinist having already performed the necessary measurements and R&R on the components. In this case, a Lotus twin-cam engine expert hot-tanked, inspected, and crack-checked everything, and advised a path where the block’s sleeves were honed just enough to get rid of the seize marks and the custom pistons were specified to fit the resulting non-standard-sized bores. A second machinist then implemented that plan. Thus, two professionals had their hands and eyes on the components before me.

Still, some folks argue that this Ikea-like method is a terrible way to build an engine. The argument against it is that, in pursuit of saving what in the end is a relatively modest amount of money, it can only introduce error and problems into the process. Those people have a point. If you pay someone to rebuild your engine, and it suffers a catastrophic failure, it’s clear who’s responsible. But if you pay them only to bore the block and grind the valves and then do all the assembly yourself and it blows up, finding the root cause becomes difficult, and assessing responsibility may be impossible. Nonetheless, it is what I do, both to hold down cost as well as to feel involved in the process.

So, having made my bed, it was time to lay in it, which is a great metaphor for what I was about to do—install the crankshaft. I laid the bearing shells into the block, smeared them with the Graphogen assembly lubricant I’d ordered as recommended in Miles Wilkins’ Lotus Ford Twin Cam Engine book, took the crankshaft out of the clear plastic bag the machine shop had stored it in, and set it in the bearing shells.

Lubing up the bearing shells with assembly paste and putting the crankshaft in.
Lubing up the bearing shells with assembly paste and putting the crankshaft in.

Lubing up the bearing shells
Lubing up the bearing shells with assembly paste and putting the crankshaft in.

And then I saw something I found alarming: There were small score marks on several of the crank journal surfaces. I couldn’t feel them with my finger, but I could feel them with my fingernail. I checked the receipt from the second machine shop and verified that the crank had been polished. Intellectually, I knew that both machinists had inspected the crank, and that if it needed to be reground they would’ve said so, but I was nervous enough that I called the second machinist. He said that, yeah, the score marks were evidence that some small pieces of metal had gotten past the pump screen and into the oil passageways, embedded themselves in the main bearings, and scratched the crank. He confirmed that he’d polished off any high spots but that the scoring remained. He said that in his opinion, for the street engine I was building, the scoring wasn’t bad enough to merit regrinding the crank.

A piece of Plastigauge on one of the main bearing journals. Light scoring of crankshaft described above is plainly visible.
A piece of Plastigauge on one of the main bearing journals. Light scoring of crankshaft described above is plainly visible.

Now, I was an engineer for 35 years and became very good at designing and building things to a set of requirements. I carry that training into the automotive world. It’s best not to look at things like this in a vacuum, but instead evaluate them in the context of what the plans are for the car. I didn’t like the fact that I could feel the scoring of the crank journals with my fingernail, but 1) Once I get this car running, it probably won’t see more than 500 miles of use a year, if that much; 2) It will be a street car, not a vintage racer, so the amount of time it spends near redline will be minimal; 3) One of the goals was, and still is, to contain cost by re-using any components that can safely be re-used; and 4) Not one but two machinists had already looked at the crank and blessed it. With that litany recited, and with an implicit prayer to “The Automotive Powers That Be,” I continued.

I put the remaining bearing shells in the main bearing caps, laid a small piece of Plastigauge down on the crankshaft journal surface, torqued everything down to spec in the recommended three stages (20, 40, and 60 lb-ft), removed the caps and bearings, and checked the width of the mashed Plastigauge against the diagram on its paper wrapper. All five squashed out at 0.002 inches, right between the 0.0015 to 0.003 spec. The machinist who’d prepared the bottom end had already performed this measurement with telescoping gauges and micrometers, but this is a quality control step that I can perform, and it makes me feel good to do it.

Matching the squashed Plastigauge to the .002-inch template on the wrapper. It’s good!
Matching the squashed Plastigauge to the .002-inch template on the wrapper. It’s good!

I was a bit annoyed at the Wilkins book because it does not appear to describe which way the crankshaft main bearing caps should face when installed in the block. I had to look in an online forum to learn that the big arrow next to the big capital F on each cap should face to the front of the engine. Oh. Duh. I then had to decide whether my naiveté was worse than the author’s omission. I decided to call it a draw.

The final steps were to install the thrust washers and check the crankshaft end play (also called end float). On the BMWs I’m used to working on, the center crankshaft bearing has integrated side-facing thrust surfaces to restrict the crank’s front-to-back motion, but on the Lotus engine, all main bearing shells are identical, and separate C-shaped thrust washers flanking the middle bearing are employed. I unpacked the thrust washers and noted that they clearly have two different faces, with one face having wide grooves, presumably to allow the passage of oil. It seemed obvious that the grooved side should face the thrust surface machined into the crankshaft, but a photograph on page 115 of the Wilkins book clearly shows the grooves facing the block, not the crank. This didn’t make sense, so I checked the factory manual (which is terse to the point of being nearly useless) and an online forum, and both confirmed that the photo in the Wilkins book is incorrect. The text description in the Wilkins book correctly describes facing the grooves toward the crank, but that description doesn’t come until three pages after the photo. These things were beginning to knock the Wilkins book down a few notches.

A first cut at measuring crankshaft float with a feeler gauge between the thrust washer and crankshaft thrust surface. Light score marks described above are clearly visible although the journal face is actually smooth and polished.
A first cut at measuring crankshaft float with a feeler gauge between the thrust washer and crankshaft thrust surface. Light score marks described above are clearly visible although the journal face is actually smooth and polished.

I did as the Wilkins book instructed and measured crankshaft end play by torquing down the other main bearing caps while leaving the center cap off, and used a feeler gauge between the thrust washer and the crank thrust face. The measured clearance was 0.004 inches (at the tight end of the 0.003 to 0.011 spec). But a better way to take the measurement is to install all of the bearing caps, and use a dial indicator on the end of the crankshaft.

I had a dial indicator I hadn’t used in years. To hold it, I found a magnetic base with an articulated arm on Amazon for $15. When the base arrived, it was trivial to mount the indicator on it, attach the assembly to the front of the block, lever the crankshaft rearward with a screwdriver, lean the dial indicator against the end of the crank, zero it, then lever the crankshaft forward. The dial indicator largely confirmed the feeler gauge, registering 0.0035 inches, which was snug but still within spec.

A dial indicator is a more accurate way of measuring crankshaft end float than a feeler gauge. Indicators with a magnetic base that attaches to the front of the block are available online for less than $30.
A dial indicator is a more accurate way of measuring crankshaft end float than a feeler gauge. Indicators with a magnetic base that attaches to the front of the block are available online for less than $30.

And, with that, the crankshaft was laid. Next week, the pistons and rods go in.

“Whew!”
“Whew!”

***

Rob Siegel has been writing the column The Hack Mechanic™ for BMW CCA Roundel Magazine for 30 years. His new book, Ran When Parked: How I Road-Tripped a Decade-Dead BMW 2002tii a Thousand Miles Back Home, and How You Can, Too, is available here on Amazon. In addition, he is the author of Memoirs of a Hack Mechanic and The Hack MechanicGuide to European Automotive Electrical Systems. Both are available from Bentley Publishers and Amazon. Or you can order personally inscribed copies through Rob’s website: www.robsiegel.com.

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