bloody barrels

Problems are increasing with the cylinders ....
The weld we made on the front barrrel exhaust port hadn't taken so I took them down to Murray for an opinion .....

The nasty exhaust port that is causing problems

not going to wreck my eyes this time

I had previously bought 50 thou over pistons ...
Murray measured the rear barrel at 60 thou over !
& that the front barrel  had 1/16" machined off the top. (basically the ridge that the head gasket sits on had been machined off.   also at a 10 thou angle
This risks the pistons hitting the heads
Stopped all work to reconsider.

I might have to get them re-sleeved & bored back to std. Hopefully I can swap the pistons over with Rocky in the USA.

This time we will build the bottom end first without balancing & check clearance with the heads to see if we can use the barrels or whether we have to machine the pistons down

pushing in the valve guides

Update Wed 4th Oct
took the barrels up to shed .... and let Wayne have another look
We tried fitting the pistons and as they wouldnt go thought that we should be able to be cleaned up at 50 thou over.

Update Thur 5th Oct
got out my kingchrome vernier scale ... & had a go at measuring
I got
Front 2.883
Rear 2.916  
even with my glasses on its v difficult to read off the thou scale

Update Sat 7th Oct
Dropped in at Murrays to pick up bearings and axle for 741 rear hub
He still thought that 50thou over was impossible.

First thing we leant was that Rocky's piston stamped 50thou were actually 2.933" which are actually 60 thou over
Also measured the thickness off the top of the piston at 5mm
Also learnt about the taper of a piston at roughly 4 thou & that the sides are different ..... thrust side & cudgeon pin side differ by 1 thou ?

Then cleaned the rust out of both bores with a drill bit spindle grinder.  Just gently through them until we could see the bore.   Luckily no major cracks.

then measured top bottom & centre
Front = 2.900"   but missing 1/16" off the top
Rear = 2.928"    broken exhaust port

pistons require 3~4 thou clearance which means we would only be giving the machinist 9 thou to play with

So looks like I will have to get them sleeved

Update Tue 11th Oct
Going to try & hone the worst barrel to see if if it will clean up for the piston  .... worth the risk