SDS - Fuel Injector Installation

When building the engine, we went to install the fuel injector bosses into the cylinder heads. There is a note in the SDS manual:

Sure enough, when we hand threaded them in, the gold bosses were touching the cylinder head. We were not able to tighten them properly, as there was not enough of the silver hex showing above the gold housing to get a socket on. I wish we had test fit these before painting the cylinders, but you can't plan for everything! 

No problem, i quietly was dying inside, but Jack got out the sanding tool and went at it! We applied some silver paint with a brush afterward. 

We didn't need to remove too much, but enough so we could tighten the hex with the socket fully engaged. We then pulled up the gold sleeve and made sure it cleared the head. 

Where to get Loctite 246!

The SDS instructions are clear that we use Loctite 246 on both the threads for the injectors into the cylinder, and the cap head screws on the injector bosses themselves. Unfortunately, this product is not sold in Australia! I asked on Facebook and the forums about where to get it, and it seems it is generally imported by people from the US when needed. Annoying. Thankfully, Adrian Port from Hobart sent me the remainder of his bottle! Gotta love the VAF community. 

It is important to use, as this is a blue medium product, so can be removed. But it has a much higher temperature rating than the normal blue loctite (loctite 243). 

This meant i could finally install the injector bodies into the cylinders. The SDS instructions call for installing the bosses into the heads until finger tight, then a further 1 1/2 turns. This seemed excessively tight - so i elected to follow the Lycoming Special Torque for the normal fuel injectors, and installed them to 60 in-lbs.

Rare as rocking horse poo!

60 in-lbs

Here you can see the amount we had to remove from the heads to the gold ring didn't contact the heads.

Loctite was also used on the cap screws into the housing.

On all cylinders, i rotated the assembly to get the most clearance from the rocker shaft cover plates. They remain very close, but not touching. We will review this after a few engine runs, and if there is any evidence of these touching in service, we will remove the rocker shaft cover plates and chamfer the lower edge to give some more clearance. 

Clearance is Clearance!

Next up is to work on the baffles, so i can complete the rest of the SDS installation.