Denzel LSR Bottom End

PLEASE NOTE: This page has been updated to include changes over time. Please don't be confused!

About The Bottom End

Of the several strokes available, we are using 74mm. The crankshaft is forged, made of very strong material, uses 8 dowel flywheel pins and has standard size main and rod journals. It was rotationally balanced.
We don't trust the aluminum connecting rods and, as the big end, length and pin are the same, we are using Porsche SC rods instead - the strongest of the 356 style.
The cylinders were made to Richard's specifications some twenty years ago by Ray Litz of Competition Engineering. They are 82.5mm bore, nominally, and consist of early, formerly 80mm bore Mahle aluminum cylinder fins shrunk onto iron liners. UPDATE BELOW.
For the 2011 season, we replaced the former pistons and cylinders with specially made larger-bore units:
- The pistons are made of a high-silica alloy which almost perfectly matches the coefficient of thermal expansion of iron - to match the new cylinders.
- The cylinders were made by taking a different VW cylinder and "editing" them.
The crankcase is a late 36hp style with solids deposition oil system.
- The case had formerly been used in racing and was bored for the Mahle 80 mm cylinders sometime long ago in its past.
- The case was updated for the 2011 season to accommodate the new bore pistons and cylinders.
The camshaft is our own grind, unique in the world, specifically designed for this particular engine.
Original Denzel engines used a Porsche style articulated cam follower / pushrod assembly so of course we are using such a system.
The oiling system is a hybrid of the Denzel full flow filter system, utilized not only for originality but also for the utility of running an external oil cooler, combined with some pieces from the Porsche 356 utilized primarily for the ease of fitting oil temp and pressure senders. An added benefit of the 356 parts is that they ensure an accurate temperature reading due to the flow of oil straight from the main galley, as opposed to the sump or other area where the sensor may not be indicative of what's actually going to the bearings.

Assembly

We mocked up the assembly many dozens of times, and when we thought we finally had it, we found that our new camshaft bound up in its bore in the crankcase! In the image below left, we see the open crankcase just prior to final assembly. As it went together, we ensured that the main bearings did not bind but we did not suspect that the cam bearings would! We checked and both the cam and the case were "at fault." Shockingly, the case bore for the cam was smaller than new specification! And, surprisingly, the new camshaft was also larger than it should have been!

To solve the camshaft fit problem, we mounted up the cam in the lathe and gently trimmed the OD of the bearing journals to 13.98mm, and then we lapped the case using a special lapping compound designed specifically for lapping aluminum - it will not continue to cut and it will not embed! To use it, you combine it with a little oil, assemble the parts, and then cause them to rub together, thus lapping the aluminum part(s). Mixing of the lapping compound with oil is illustrated in the image below, right.

Do note in the image above left that the camshaft gear is both bolted and pinned.

After the bottom was bolted together, the pistons and cylinders were installed, however, this was an iterative process requiring uncounted cycles of assemble, measure, disassemble, alter the cylinder shims, and repeat. The goal of the repetitious cycles of installation and measurement were to ensure that the cylinder shimming was perfect so that our CR is exactly where we want it, and that both cylinders are exactly identical in the power they produce. Here are the pistons and cylinders, carefully balanced, and a trial assembly.

UPDATE: For the 2011 season, here are some images of updating our pistons and cylinders.

Below, we see the new cylinders - note the relocated head-stud holes!

Now, we can see the pistons that fit inside the new cylinders:

END UPDATE

On right, the bottom end has been completed and the heads have been attached only as a means of retaining the cylinders - they, themselves had yet to be bolted on when this picture was taken.

The connecting rods below we decided not to use due to the inherent risk of using aluminum rods with an unknown previous number of cycles.

Below is a Denzel crankshaft. Note the counterweights and also the very beefy web that crosses between rod journals 1 to 3, and 4 to 2.

UPDATE: The assembled bottom end.

Here, we see the new-in-2011 bottom end, almost ready for the tin and accessories.

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