Gday All,
I?ve finally collected the gear to build a new bottom end for the A7 plunger and have run into strife.
The original cases were welded up, ?sprung? and generally stuffed.
I managed to get another set using extortion, cash and some pleading.
The cases are stamped with the same batch number so they are probably a set.
The problem is that with the crankcase locating dowel fitted, nothing else lines up.
The holes for the two studs near the locating dowel won?t line up and can?t be fitted.
The crankcases at the gearbox and sump don?t line up. The suspicion is this engine was originally built without the dowel pin.
If the dowel is taken out, and all the bolts tightened up, things line up reasonably well.
How does this sound for a fix?
1. Loosely fit all the crankcase bolts without the dowel.
2. Bolt on the gearbox and sump to align the cases then tighten everything up.
3. Pin the cases somehow ??
4. Get a new timing bush line bored.
5. Get the deck machined parallel to the crank.
6. Get new camshaft bushes line bored.
Before anyone suggests I hand it over to an expert, been there done that.
All the work was done with the dowel in and the adjacent studs out.
With a new timing side bush, the crank spun sweetly but as the cam was bent 2 thou from the nitriding it was tight in one spot.
After the cam was straightened, it was tight everywhere. On removing the dowel, adjusting the cases and fitting the missing studs, it slopped and banged about with huge clearance. The bushes had been reamed to death. But the crank wouldn?t spin sweetly.
It?s difficult to blame the machinist as I handed the cases over with the dowel in.
Before he has another go I'd like to find any hints that might help us.
This brings up another question.
With new bushes (that haven?t been reamed), the camshaft spins freely in each crankcase half but tightens up when the cases are fitted together. It can be turned easily with a spanner but not by hand. Does a straight ream of the individual bushes fix this? Does a line bore or line ream fix it. Should I fit a Triumph motor?