Background
In late January I was able to get out in my MGB GT V8 for the first time and experienced some Disharmony with the Harmonic Balancer. This was a longer break than usual because we had been back home in England since mid-December for Christmas and New Year, and that had prevented me from getting in some periodic drives. The drive had gone fine until about 2 miles from home. I had just stopped for petrol and upon pulling away I heard a metal jangling noise. Sounded like something metallic was dragging on the road. It went away at one set of traffic lights and then returned at the next but I nursed the car home and started to investigate.
Investigation
My initial thought was maybe the water pump had gone since the noise seemed to be RPM related but a screwdriver stethoscope suggested no. Looking a little harder and listening more closely, I traced the noise to the engine crank pulley area. There’s not exactly a lot of space at the front of the block but I could see enough to determine the issue was the harmonic balancer – it had completely separated and the outer piece had gone backwards and was jangling behind the remaining pulley and the front of the block.
Removal & Part Identification
Now, everything on my V8 conversion is an adventure because it is a custom car and I didn’t build it. So, when something goes wrong, it’s an investigation, followed by part research, trying to find a supplier for a part etc. – you get the picture. This is not a pick up a Moss Motors or other vendor catalogue or website and order the part. This adds to the “adventure” of a repair because this has to happen before you can even figure out how to actually start the repair itself, which, also doesn’t often follow any general MGB procedure.
On one of the warmer weekends we had I started the process of getting access. This involved a radiator drain and removal. With the electric fan mounted to the radiator, I wasn’t sure if I could get the fan and radiator out as one piece and so elected to remove the water pump pulley to provide some extra working room. This all went relatively smoothly and I was able to get at and remove the belt pully attached to the front of the inner remains of the harmonic balancer. With this removed I was actually able to retrieve and pull off the outer piece of the harmonic balancer. Now just to remove the main crank nut and start the part search. Yeah, not so fast!
What size is this bolt? It’s 15/16ths on my Oldsmobile version of the 215 engine, what’s the socket size I didn’t have? Need I say more. Once I had the sockets I could at least try. I do have an air impact wrench but its low quality and not much grunt. So long rachet and some grunt will do it. I could not for the life of me get the crank bolt to move! Nope – even in gear and with handbrake and breaks applied by my lovely assistant the car would move not the crank nut. Ho hum.
I engaged some of the club’s collective brain trust, naturally including John Mangles, and also Rich Berger as a fellow conversion owner. John was able to lend me a breaker bar and had some suggestions and Rich Berger suggested using the starter motor to break it loose – something he had done before. I eventually tried using the starter motor and this was the break through moment. I checked the rotation direction of the crank, double checked myself using a nut and bolt to make sure I wasn’t losing my mind and then managed to set the breaker bar and socket in place and hit the starter with the ignition. Bit of a noise and the front of the car lifted slightly but low and behold upon inspection the nut was loose!
I got the remains of the balancer off and was able to see the part number of 578785 on the back. From research I had done this confirmed it as an Oldsmobile harmonic balancer. Now to get a replacement. Again, not so fast because these are not readily available so now we are into rebuild land. It seemed there were a couple of options and I ended up using a company called Damper Doctor in California. John knew of them but hadn’t used them. It seems another option would have been the aluminium V8 specialists D&D.
I sent off my harmonic balancer pieces as Damper Doctor didn’t have an available one. They did the work in a couple of days and shipped it back to me and I had a nice clean and refurbished harmonic balancer to work with.
Repaired Parts Reinstalled
Reinstall is the reverse of removal I think the Haynes manuals say and for the most part that was true. I did have a bit of an issue getting the harmonic balancer onto the crank at first but the seemed to be a simple case of the paint on the refurbished balancer making the fit very tight. Some “finessing” and using a rubber mallet seemed to do the trick. I was a bit paranoid about checking the timing mark but after pulling the #1 spark plug the piston seemed to be at TDC with the timing mark on the zero. I didn’t check the valves so hopefully that was TDC on the compression stroke. Everything went back as planned and after a couple of test drives all seems to be OK. Looking forward to being able to do the Triumphant Tour/Missouri Endurance Rally in the GT in April.
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