This is a job that I had hoped to work on during the summer but in never happened. Finally I have the time and I’ve started rebuilding my 1967 MGB GT engine.
The engine is a bit of a Frankenstein build with parts from a 1972 18V engine combined with parts form the original 1967 18GB engine. In this part of the build I’m installing the 1967 MGB crankshaft into the 1972 engine block. There are a few reasons I’m doing this. Firstly, the 1967 crankshaft was the original that was damaged when I threw a rod bearing and has been reground to .020, balanced and straightened. Some folks believe these earlier crankshafts are better than the more recent ones as well.
The 1972 block was chosen primarily because it has the cutouts for the larger intake valves that are in the big valve head that will be installed. These cutouts can be seen in the image below. Another factor for using the newer block is that it’s way cleaner internally than the original MGB 18GB engine. Both the original block and the newer block were redone about 40,000 miles ago but the 1967 block is full of crud in the cooling jacket and I imagine the oil passages might be ugly as well. I wonder whether the folks that rebuilt the engine cleaned it at all. I’ve documented some of the horror stories before.
After some cleaning the new .020 main bearings dropped easily into the block. I don’t have a clue what I’m doing so a neighbour came over to help. He knows less about engine building than I do but we are smart and we have the internet.
I have never used Plastigage before but figured it wouldn’t hurt to check out clearances before we proceeded. We placed the redone crankshaft onto the block and installed the middle cap at a torque of 70 lbs to see what happens.
Here’s the result, not quite a clearance of .002 which is what it should be. The funny thing about this exercise is that if the clearances were a little too tight or loose what does one do? I guess either carry on and don’t worry about it (budget) or have the crankshaft reground to the new size required (more money).
Lots of assemble lube was smeared on the bearings and amazingly enough we remembered to install the thrust bearings properly. After torquing the center bearing to 70 ft-lbs I checked the crankshaft end float and it’s at .004 which is perfect. Luck is on our side almost!
All of the other bearing caps installed smoothly and the crank rotated beautifully so I figured we were done but of course that wasn’t to be the case. On cleaning things up I discovered some metal filings on the end of the crankshaft. While these were outside the engine I decided not to risk anything and removed the crankshaft once again for a cleaning. The reinstall went smoothly now since we know what to do!
Next step, install the pistons.