09-03-2025, 10:35 AM
Hi
Having recently done an engine rebuild, here are my top tips:
+1 for slipper pistons, noticeably reduced friction and slightly lighter
+1 for balancing rods at both ends
I used cap head 12.9 grade screws for the little ends, with red loctite. Gudgeon pins must be free in cold pistons, a little "working" may be needed with thin lubricant to take off microscopic high spots.
+1 for at least statically balancing the heavy flywheel / clutch. I didn't bother with the crank.
I used new standard valve springs, which seem fine to 4500 RPM but I rarely go above 4000.
+1 for silicone base gasket (and sump gasket)
A high compression head will increase top end power, but won't be as smooth with only 2 bearings. It can be left as a later mod if desired.
Ignition timing is reliant on multiple pairs of gears all with backlash. Minimise this if you can, even dynamo end float can cause timing scatter.
I didn't modify the oil system, I just use modern oil which is vastly better than anything in the 1930's and change it regularly.
I did the front cam bush mod with a cap head screw tapped into the bush to hold it tight. I didn't add O rings as it was snug in the crankcase.
Having recently done an engine rebuild, here are my top tips:
+1 for slipper pistons, noticeably reduced friction and slightly lighter
+1 for balancing rods at both ends
I used cap head 12.9 grade screws for the little ends, with red loctite. Gudgeon pins must be free in cold pistons, a little "working" may be needed with thin lubricant to take off microscopic high spots.
+1 for at least statically balancing the heavy flywheel / clutch. I didn't bother with the crank.
I used new standard valve springs, which seem fine to 4500 RPM but I rarely go above 4000.
+1 for silicone base gasket (and sump gasket)
A high compression head will increase top end power, but won't be as smooth with only 2 bearings. It can be left as a later mod if desired.
Ignition timing is reliant on multiple pairs of gears all with backlash. Minimise this if you can, even dynamo end float can cause timing scatter.
I didn't modify the oil system, I just use modern oil which is vastly better than anything in the 1930's and change it regularly.
I did the front cam bush mod with a cap head screw tapped into the bush to hold it tight. I didn't add O rings as it was snug in the crankcase.