Brush Honing

An Engine builder needs to understand that there is a vast difference between rings that are merely seated and those that are seated with some attention given to detail. This is true for any piston-driven vehicle or equipment. If incorrectly done, the same basic problems — oil consumption, smoking, and lack of power — that may have prompted the work in the first place remain. Furthermore, correct and conscientious honing is one of the most misunderstood aspects of a successful engine freshening or rebuilding.

Consider The Cylinder Wall

By definition, honing is the surface preparation of the cylinder walls that allows the properly seated rings to work correctly.

Unless you've studied them, cylinder wall finishes all look pretty much the same. It's very difficult to see a honed finish whether it is coarse or fine, properly or poorly done.

Think of the honed finish on the cylinder wall as sandpaper. Now imagine the narrow, fragile ring face rubbing against 50-grit sandpaper. The ring is actually bouncing from peak to valley, rounding off and tearing up its face and creating unnecessary heat that damages its temper. After all that, we then ask the ring to be happy and go 150,000 miles!

A finer-honed cylinder surface is more like 300-grit sandpaper. As more of the grit contacts the delicate ring face, less heat buildup is created during seating, and the ring is stabilized so it can be honed in rather than broken in.

Engine builders who are willing to settle for the bore finish supplied by many sleeve manufacturers and most machine shops need to be wary. Most manufacturers and shops will err on the side of having too coarse of a cylinder finish. Generally, they are trying to ensure that no matter what the "average" customer does wrong in assembly, during the initial start-up and break-in of the engine, the rings will seat without question. However, this is at the expense of ring longevity.

Instead of settling for this "average" finish, check the manufacturer's recommended hone grit for the type of ring material you are using. Then get in touch with Brush Research Manufacturing Company, Inc. (BR), 4642 E. Floral Drive, Los Angeles, CA 90022. Get their input and use their hone as per their instructions, which will generate the correct 45 degree cross-hatch. Or, have the machine shop use one for the finish hone.

Practical Tips

Prior to honing, have the block bored with a torque plate. This allows for head bolt torque distortion that affects the bore shape when the heads are torqued in place. The torque plate should be used with the head gasket, and the torque plate bolts thread lengths should be the same as the head bolts.

If you use a torque plate, you might want to compare the ring end gap dimension with and without the plate torqued up.

Each engine design is a little different and some blocks are more affected by torquing than others due to the head bolt location and different materials.

If you are wondering about your block and whether it's affected, check it. With all the threads cleaned and oiled, torque the head, head gasket, and main caps on the bare block. Compare the sizes or the bores near the top of the block to those with the head off. The whole idea of this is to make a round hole for the ring to operate in at top dead center (TDC) where as much compression pressure as possible needs to be retained. If you're freshening a racing engine built by one of your competitors and the bores measure out of round, consider that it may have been bored with a deck plate.

Finish with the correct BR hone using honing oil, which will help cool the brush hone and cleanly cut the surface — unlike some production-type rigid hones that, if used to fast or with worn stones, will tear up the wall finish.

Don't hone in the solvent tank using parts solvent. The hone will tear, fold, and rip the bore finish. You won't be able to see the damage with the naked eye, and the ring longevity will suffer once again.

After honing, wash the bores and block with hot, soapy water. Use a stiff round brush to clean the bores, oil them to prevent rust, and use only clean oil and a lint free rag to clean the bores again before assembly. Never use cylinder sleeve coatings that are slippery. Avoid synthetic oils; they won't allow the rings to seat. After engine break-in, however, synthetic oils are fine to use.

Now that you have a nice "round" hole bored with a torque plate, have brush honed the final finish with honing oil, and cleaned the bores and block with hot, soapy water, there are just a few more steps before it is time to seat the rings.

Proper ring seating is just as critical as all of the careful preparation you've done up to this point; don't leave this part to the customer!

Before Seating Rings

1. Gap the rings while fitting them square in the bore.
2. Detail the ring ends by smoothing the sharp edges that would keep the ring from moving in the groove.
3. Space the end gaps as per the instructions from the manufacturer.
4. Lightly oil the bores and ring lands.
5. Carefully install the pistons and rods in the bores.