By Freddie Heaney, January 25, 2015
It is probable Total Seal’s Keith Jones exhibited an aptitude for engineering at an early age. Given a knack for simplifying the concept of cylinder sealing, his latest business card is wondrously effective. Representing a flexible, transparent plastic protractor, it confirms cylinder cross-hatch honing angles in moments.
Of course there are formulas to check cross-hatch angles, but often the simplest method is a protractor. “Just peel the translucent backing off the card to aid visibility,” says Jones, “and press the card into the curvature of the cylinder wall, aligning its top edge with the deck surface.” To determine the included angle of the cross-hatch honing, simply double the angle displayed on the card—if it reads 22 degrees the true included angle becomes 44. Used on both small-block Chevrolet and Ford engines, the 45-degree honing angle is the most common.
Yet some engines like flat-sixes or flat-fours (Subaru) and particularly those with long strokes operate better with a more vertical cross-hatch angle: 60degrees. This promotes oil movement all the way up to the top of the bore. These engines trade a little more blow-by for increased oiling to the top of the cylinder, which results in less wear.
As the cross-hatch angle becomes more vertical it increases the movement of oil up and down the cylinder wall. Though it returns oil more rapidly to the sump, it also facilitates blow-by.
Most honing troubles are caused by angles that are too flat
By contrast as the cross-hatch angle becomes flatter, blow-by is reduced as the oil tends to move left and right rather than up and down and into the sump. “However, cross-hatch angles that are too flat,” advises Jones, “can cause numerous oil control problems, including smoking at idle, where the intake vacuum is high, or when cruising at part throttle or under engine deceleration.”
How so? As the cross-hatch angle becomes flatter it is more difficult for the rings to return the oil to the sump. This condition leaves more oil remaining on the cylinder wall and the increased intake tract vacuum captures the excess oil, contaminates the combustion charge, and emits it as smoke
Cross-hatch angles are determined by how fast the honing head rotates and how quickly it cycles up and down. Combining the recommended belt-driven pulleys on older honing machines, for example, does not mean the cross-hatch angle will be correct. It needs to be checked.
Total Seal, Inc