Weber Conversion
When we fitted the progressive carb to my 1.7l camper, we spent a lot of time chasing round during the tuning stage, to find that the tappet clearance on inlet #3 was zero, despite the fact that I'd set the tappets a few months earlier. This was a warning. I should have listened.
Shortly after the carb was fitted and tuned to our satisfaction, I took the camper, fully loaded with dogs and partner, on holiday to Wales, via the Peak District. Those in the know will realise that this means hills, and lots of them.
The van performed well, giving decent mileage, never complaining about the strain. Despite it shaking the new EMPI exhaust box loose -- yet another warning I ignored -- I was happy. Until the drive home.
About sixty miles from home, a nagging doubt about the power output and the blowing noise -- more exhaust trouble I thought --was suddenly impossible to deny. The next flat stretch proved the problem, as I was unable to get the van to reach 60 mph.
We pulled in at services, 40 miles from home, and it was immediately obvious that it was firing on three cylinders. Reaching over to pull the HT lead from #3 I burned my arm on the induction manifold. Bad mojo. When the engine is hot those tubes are barely warm. I also noticed that the rubber boot connecting the #3 manifold to the body had split.
I confirmed that the other cylinders were firing, and made a decision. I was not inclined to start messing around under the van in a car park only forty miles from home. So, I pulled the HT lead from #3, taped up the split boot and drove home at 45 mph.
The next day I pulled the manifold to reveal that the metal gauze we had fitted in the manifold body had disintegrated. Further poking revealed that the guide for inlet valve #3 was out of the head, slapping up and down on the stem. Time to pull the head. Head pulled, I could see that the seat for #3 inlet was free, and had beaten a hole about 1/4" deep into the head, the bore was covered in metal paste, presumably the remains of the head and the gauze.
I sourced a replacement pair of heads for virtually nothing, and with all of the parts ready and waiting for the weekend, I highsided my motorcycle on the way to work and shattered my collarbone. Two months in a sling. Still in physio.
Lessons learned:
- Tappets don't just lose .006" in a couple of months. They certainly don't torque themselves up afterwards.
- Look past the problem. All of the little things add up, everything pointed towards this one failure.
- Don't let creeping problems creep up. If you're not sure, stop, make a cuppa, cool down, start up, listen.
- Use a brass wire gauze, not pressed aluminium.
- Ice is slippery, 120BHP is too much.