Something similar happened to me years ago driving down the A1 near Catterick. I was taking the wife to Manchester in our Austin Allegro VDP Auto (I know, don't laugh too loud). The day before I had fitted a new exhaust and it had been a bit of a rush. Anyway, doing 65ish one second, then BANG, CLANK, the car took off like a bloody rocket, the rev counter went to the red stop and tried to fight its way off the clock face and the car was filled with the sound of loud screaming (the engine not us), I was rooted to the spot for what seemed like minutes but was really only a few seconds until I realised the traffic was starting to build up & there was a real danger of a nasty ending real soon! No sliproad or hard shoulder to take, just hedgerows, fences & deep ditches, so I stood on the brakes; not slowing down at all, stood on them harder, car began to judder so badly I nearly lost control of the wheel despite my hands being welded to it! Put it in neutral & the motor screamed so loud, my heart was in my mouth, I was expecting pistons, rods & bits of white hot block to come flying through the bulkhead LOL. I finally managed to stop it after about a mile or so but couldn,t shut it down by removing the key or the battery neg wire. I had to use my wire cutters to cut through the throttle cable!!! What had happened was, I had fitted the exhaust manifold clamp UPSIDE DOWN the day before, & this had come loose and allowed the frontpipe to drop onto the throttle cable which ran just below the joint! Buggered the head gasket, buggered my suit, and generally ruined the mood, but we lived to fight another day, and it was DEFINATELY a good lesson learned!
