Setback with SABB

My SABB reassembly effort came to a screeching halt when a 5/16" bolt hole stripped on the no. 1 head.

Things had been going very well. I had fitted both heads with their bolts snugged up until I could obtain a torque wrench with a 1/2" drive for the 24mm socket that Bob had loaned to me. I had then decided to proceed with installing the injectors and fuel lines

For the injector work I was careful to use the 3/8" drive torque wrench that Bob had loaned to me to tighten the injector bolts to the prescribed 22 ft-lb. For the fuel line bolts the book stated that the torque for all other 3/16" bolts should be in the range 14-17 ft lbs. This seemed a bit tight to the feel of my hand but I was dealing with fuel line which had to be well sealed. I fitted both fuel line bolts on the no. 2 head to 15 ft lbs with no problem. I then started torquing up the two bolts on the no. 1 head in slow steps seesaw fashion when the one on the head stripped out.

The accompanying photo shows problem area, which is trickier than it may appear because that bolt hole is the channel through which fuel passes from the injector pump to the injector. The bolt has a slot along its length, no doubt to allow fuel to pass through. Tapping for a bigger bolt would require modification of the short segment of fuel line between the edge of the head and the injector, shown in the photo. A new bolt would have to have a slot in it.

I need professional advice on this one and will send a message to Colin.

This is a big shame because even at my slow and deliberate pace I was on track to be ready to test fire the engine well before sundown.

There was nothing to be done but to take the no. 1 head off the engine and remove the injector and 4 studs in preparation for yet another trip to a machine shop. After cleaning up the cabin I consoled myself with a dish of yohhurt and fruit.

I'll note some technical things for the record.

I measured the distances from the pistons at TDC to the top of the cylinder. The gap for no. 1 cylinder was .047" and for no. 2 cylinder it was .043". Colin wanted me to check this to be sure that one of the rods had not bent. With a difference of .004 in my measurement I figure that both rods are either straight or bent the same. [Note: I've just thought of looking in the manual, which states that the piston top clearance is 1-1.5 mm, which equates to the range .039-.059"]

I fitted the no. 2 injector with the proper copper seal which was 2 mm thick. I fitted the no. 1 injector with two thinner seals which had a combined thickness of 2.5 mm.