03-03-2018, 04:30 PM
Thanks, Dave and Zeto, for your replies.
I agree that drilling the bolt to accomodate the pin is questionable but I assume the engineers who designed it that way left enough reserve to take the stresses.
Capheads, and I assume you mean those with sockets, would hold the big ends together OK but the essential feature of the present bolts is the chamfer which allows the bolt head to pass the camshaft without touching. They are extremely close! On no account may the bolt turn and then foul the camshaft. That's what the pin is for.
Using Austin 10 bolts, as you suggest, is an interesting idea and would imply grinding off the chamfer but I doubt that there would then be enough material left in the bolt head to subsequently hold the vertical pin. A solution could be to cut a slot in the head, fit a steel tongue (would brazing hold it?) which protrudes below the head and finally grind the chanfer.
Phoenix crank and rods would be the ultimate solution and I assume the big end dimensions would allow more clearance in the crankcase for them and their bolts to pass the camshaft. Yes, it is a proper Speedy crankcase. A crack in it was repaired by metal stitching about 10 years ago.
At the moment I have enough of these big end bolts but if new ones were available, (as they were about 40 years ago!) I would be interested in having a few in reserve.
I agree that drilling the bolt to accomodate the pin is questionable but I assume the engineers who designed it that way left enough reserve to take the stresses.
Capheads, and I assume you mean those with sockets, would hold the big ends together OK but the essential feature of the present bolts is the chamfer which allows the bolt head to pass the camshaft without touching. They are extremely close! On no account may the bolt turn and then foul the camshaft. That's what the pin is for.
Using Austin 10 bolts, as you suggest, is an interesting idea and would imply grinding off the chamfer but I doubt that there would then be enough material left in the bolt head to subsequently hold the vertical pin. A solution could be to cut a slot in the head, fit a steel tongue (would brazing hold it?) which protrudes below the head and finally grind the chanfer.
Phoenix crank and rods would be the ultimate solution and I assume the big end dimensions would allow more clearance in the crankcase for them and their bolts to pass the camshaft. Yes, it is a proper Speedy crankcase. A crack in it was repaired by metal stitching about 10 years ago.
At the moment I have enough of these big end bolts but if new ones were available, (as they were about 40 years ago!) I would be interested in having a few in reserve.