Announcing the Merc 888

[Tim Kurcz]

Nice project Tim,
Well getting fuel and lube around might be a bit of an issue. One thing you might consider is to make a regular dry sump lube system with an oil pump. Reed block could stay in without the reeds and stops. The center main bearing carrier could be machined to allow the oil to drain down where it cam be pumped our. Exterior oil line to spray nozzle's should due the trick to keep the rotating system and the back side of the piston lubricated. For starting you can install a primer system to spray fuel into the intakes. With an electric pump this would be easy. This assumes that the carb will be in a pressure box.

Good luck,
Alan

Hi Alan, et al,

Here goes on Q&A:

1) Great thought was given to crank/rod oiling. For this reason, single point mixture entry was chosen. This forces mixture to travel from the front bank diagonally through the crankcase to feed the rear bank. An 8:1 fuel-oil ratio will slobber the internals. As noted, reed cages (bronze) will be installed without reeds, and the center main will be perforated to encourage further inter-cavity mixture migration.

2) Automotive crank trigger inductive (or capacitive discharge) systems are designed to fire one coil each, in sequence. Discussion with MSD and Pertronix (so far) suggests that firing two different cylinders simultaneously requires twin parallel systems (like aircraft or top fuel engines). Both are fine solutions, but bulky and expensive. Instead, a test rig will determine if four simple prox. sensors will fire four GM HEI modules through eight coils, or eight HEI modules firing eight coils, etc. I not successful, twin belt-driven VW Type I distributors will be considered.

3) As pointed out, RR Merlin-style blade and fork style rods are far and away the most elegant solution to support directly opposed cylinders. Yes, the existing Mercury crank can be altered at great trouble and expense to accommodate custom rods, only to compromise balance and torsional rigidity. Better yet, a press-pin crank could be assembled with beefier journals, and one-piece fork & blade rods running on separate needle bearings.

This is an experiment to determine if a turbo scavenged, open crankcase two-stroke will behave sufficiently well to consider future development. It's convenient that 60+ year old Mercury are plentiful to use as a base (they also happen to look bad-***!). If the engine actually runs and behaves itself, my thoughts are offset rods, separate pumping chambers, and loop scavenging........




Tim