1776 Engine
For the Megasquirt Turbo Sandrail build, I decided to build a new engine. The first thing to decide was the displacement. The Manx was a stock 1600 and I wanted something a bit bigger this time. That left three obvious options: 1776, 1835, and 1915. Just about everyone I talked to disliked the 1835 due to reliability issues with the thin cylinder walls. I like reliable, so I quickly decided against the 1835. Many friends liked the 1915, but I was a bit uneasy about the amount of material that needs to be cut out of the case, and discarded the 1915. That left me with the 1776. Given that I’m going to turbo the motor, the 1776 should be enough engine for me.
The local dealer here in Eugene helped me select the components for the engine. We started with a new aluminum case that was clearanced for the 90.5 cylinders. The crankshaft was a CB Performance forged counterweighted crank, and the camshaft is was also a CB Performance product (I think they call them “eagle” cams). I had an existing set of almost-new stock heads that we had clearanced for the cylinders. Rods were CB-Performance uni-tech rods, and pistons were Mahle forged.
The CB-Perfofrmance crank provided extra lift, so I stayed with 1:1.1 rocker arms, but added one of the heavy duty rocker shaft kits from bugpack. This kit replaces the stock rocker shaft with a heavy duty model that uses shims between the rockers instead of the stock springy-washer things. The bugpack instructions were poor, so expect to spend a little time playing with one of these to get it right if you’ve never done it before. Basically, the process involves adjusting shims around on the rocker shaft until you get rid of the play, but at the same time not so tight that your rockers bind. In addition to the heavy duty rocker shaft, I added some high-rev springs.
Pushrods were the heavy duty (and expensive) chromoly type, probably another bugpack product. Pushrod tubes were the bugpack windage tubes (these tubes gave me endless problems with squashing the seals in the heads when I torqued the heads down, perhaps because they were stiffer than normal tubes and harder to squash into shape).
The mechanical fuel pump was not installed, and a block-off plate put in its place. The reason for this is that I will be using a high-pressure fuel injection pump instead. The block-off plate can be drilled out and used for an additional crankcase vent or a turbo oil return.
I purchased a new Bosch 009 distributor. Currently the advance is still enabled, but the advance will have to be locked out eventually so the megasquirt can do the timing.