After a piston seizure and strip down we are now at the point of putting our ’58 Brum back together (thanks to Brian Marshall and others for their help thus far), but we have a few questions I’m hoping someone can help with before we start:-
1) The long bolts that hold the cylinders onto the crankcase, what should these be torqued to ? and should they have split washers on ?
2) The nuts for the cylinder head are nyloc nuts which we presume aren’t original, should we fit new plain nuts and split washers or just new nyloc nuts or what ?
3) What coolant do we put in the radiator on refill ?
Hopefully when this is all done we can look at the cause of the problem, the pilgrim pump.
Hi, The four bolts holding the crankcase to the barrel should each have a deep spacer/washer approx 5/16″ thick, up to 3/8″ thick, and it is important that the bolts do not bottom in their holes. Thoroughly clean out the holes before installing the barrel, because debris and gunge tends to accumulate in them, and this can prevent the bolts going ‘home’ properly. Put a smear of silicone sealant under the head of each bolt and both sides of the spacers, before tightening them down with an open-ended spanner and one hand.
The cylinder head nuts should not have spring washers as they would chew up the aluminium of the head. I’m unsure as to whether or not Nyloc nuts were ever used by Matt Holder, but I have never seen any, and I would use the correct special ‘deep’ nuts with plain washers. Torque settings were never specified, and it is a matter of using common sense, gradually tightening the nuts, starting in the middle and working outwards, and switching from front to back diagonally/alternately. When all 16 nuts have been tightened once you can start again in the middle and tighten them again, using a short spanner, NOT a socket set. After the bike’s first run, and things have bedded down a bit, the tightness can be rechecked, again starting in the middle and working outwards. Put a smear of ‘Copperslip’ or other anti-seize compound around all 16 studs before lowering the head down over them. Don’t forget to install new cylinder base rings !!! Also the paper rings and/or a smear of silicone around the outer barrel/crankcase joints.
For coolant use ‘soft’ water such as rainwater, especially if you live in a hard water area, with 30% Glycol antifreeze/corrosion inhibitor. Leave this in all year round.
There is a lot more to say on this subject, as I for instance, use guide rods to lower the barrel down fair and square before installing the bolts, and piston ring compressors rather than my fingers, to avoid breaking rings, but I could go on all night about it. The main ingredient is common sense and care ! Good luck.
Many thanks again Brian for your advice. I have found the following article by Roger Moss with regard to the cylinder head torques which for the uninitiated like me, who is notorious for breaking things by over tightening, is very useful.
With regard to the “correct special ‘deep’ nuts” for the cylinder head, what is “special” about these and where can they be obtained.
Yes it would have been nice to have piston ring compressors as we have broken 2 rings in the process of getting the barrels back on (thanks to Richard of scottparts.co.uk for his advice on how to install the new ones), that was before we realised its easier if the pistons are staggered rather than trying to get both in at the same time, again probably common sense, but when you’ve never done it before 😕 but we have now got the barrels back on 😀 first step complete !
Brian mentions “guide rods” to help with fitting the block, and I recently read in an old Yowl that the revered Tom Ward also recommended it. It would be good to have some details of the procedure.
To answer two separate questions :- The correct ‘deep’ cylinder head retaining nuts are half an inch deep, so have plenty of grip onto the studs.
Tom Ward’s guide rods are very simple to make, and you need two of them. As they carry no load they can be made out of mild steel rod, 3/8″ diameter, and 5.5″ long (minimum). Put about one inch of 26TPI cycle thread on one end, and a screwdriver slot on the other end. To use them, screw them into two of the cylinder retaining bolt holes, one on each side, just finger tight. These help the barrel to be lowered smoothly and ‘square on’ to the crankcase, and when the barrel is ‘home’ just remove them, using a screwdriver if necessary, and replace them with the retaining bolts and spacers.
Mine actually are Tom Ward’s, and they were given to me many years ago by the late John Hartshorne, at a time when he was without a Scott for a few years in the 1980’s. John was Tom’s business ‘sleeping partner’, and company secretary at Ward Motors Limited.
I also have Tom’s old notebooks, which are full of interesting information.