11-02-2018, 07:58 AM
From limited but observant experience with other engines, relative oil consumption can be puzzling, Some engines with broken rings, basic oil rings, use little. Others with multi section oil rings use ample.
Eons ago with the original wide ring pistons my car moderately worn used almost no oil. A similarly worn engine but with thin ring split skirt pistons used lots. Even after a rebore the 4 ring pistons used a pint per 300 miles of hot main road running. This with the split ending in a relief below the top oil ring.
Some years ago I asked about typical consumptions; few replied and as I recall only Ruairidh claimed a low figure. Some claim reasonable consumption without baffles.
If, as the photo implies, RRs observation is correct, could explain much. Top rings with thick chrome plating often had large bevels both edges.
I assume the rings are not some gross oversize gapped down.
I presume the land below bottom ring is reduced dia.
If desperate could turn/file a slight relief below top oil ring and drill holes breaking in to. One rail of oil rings can have tiny 5 deg taper filed onto outer edge and fitted upward. If can locate a source or good used ones, wavy spacers behind oil rings will help, assuming room. If not already tapered or bevelled can also chamfer top edge of comp rings, stopping near gap.
Are the very heavy multigrades so thick when cold that the rings cannot handle? (In conventional engines less is thrown about to compensate)
Do others adopt the huge oil trenches in the cap?
Is the piston illustrated the common pattern? The last ones made here had the slot below the ring groove.
Eons ago with the original wide ring pistons my car moderately worn used almost no oil. A similarly worn engine but with thin ring split skirt pistons used lots. Even after a rebore the 4 ring pistons used a pint per 300 miles of hot main road running. This with the split ending in a relief below the top oil ring.
Some years ago I asked about typical consumptions; few replied and as I recall only Ruairidh claimed a low figure. Some claim reasonable consumption without baffles.
If, as the photo implies, RRs observation is correct, could explain much. Top rings with thick chrome plating often had large bevels both edges.
I assume the rings are not some gross oversize gapped down.
I presume the land below bottom ring is reduced dia.
If desperate could turn/file a slight relief below top oil ring and drill holes breaking in to. One rail of oil rings can have tiny 5 deg taper filed onto outer edge and fitted upward. If can locate a source or good used ones, wavy spacers behind oil rings will help, assuming room. If not already tapered or bevelled can also chamfer top edge of comp rings, stopping near gap.
Are the very heavy multigrades so thick when cold that the rings cannot handle? (In conventional engines less is thrown about to compensate)
Do others adopt the huge oil trenches in the cap?
Is the piston illustrated the common pattern? The last ones made here had the slot below the ring groove.