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Honing cylinders with a Flex-Hone during engine rebuilding.

Fix A Connecting Rod Knock - GM 4.3 V6:

Engine Rebuild Part 4 - Cylinder Honing And Block Cleaning

May Also Apply To Chevy / GMC
350 Cubic Inch V8 Engines

 
In This Article:
The cylinders are honed with a ball hone. Head gasket residue is cleaned from the engine block deck. The cylinders are washed with laundry detergent.
Related Articles:
Skill Level:
4 (Advanced)
Time Taken:
About 4 Hours
Author:
Bruce W. Maki, Editor
Project Date:
August 2011
By Bruce W. Maki, Editor
By HammerZone.com Staff
Start >>

 

In Part 3, I removed the old crankshaft from the engine.

 

I could have skipped this whole section on honing the cylinders... if I didn't want to install new piston rings when I replaced the crankshaft.

If new piston rings are installed, the cylinder walls MUST be given an appropriate scratch pattern. The scratches help the new rings "wear in", and they also hold oil on the cylinder wall, which reduces the wear on the piston rings and the cylinder. It might even improve fuel economy because the engine has less internal friction.

The best way to get the proper scratch pattern is with an electric drill and a ball hone, which I will demonstrate below.

 

To keep grit and debris away from the camshaft during cylinder honing, I placed paper towels over the 3 exposed sections of camshaft.

I tucked the paper behind the cylinder wall portion of the engine block casting. (I'm not planning on replacing the camshaft.)

Notice how shiny the cylinders are... this happens after 160,000 miles of use. Shiny is NOT good.

Covering camshaft with paper towels before honing cylinders.
 

 

Oil filter adapter, GM 4.3 V6 engine.
A Word Of Caution:

Note the oil filter area at the rear of the engine (driver's side). On larger trucks, the oil filter goes here, but on the Blazer/Jimmer, they install an adapter here and run oil lines up to the front of the vehicle.

I forgot to cover up this area when I first turned the engine upside down, and I became concerned that some dirt may have gotten into the oil passageways. I later realized that this isn't a serious risk because there is a check valve on the "clean" side of the oil system (arrow 1). The check valve holds the oil in the galleries when the engine is shut off, preventing all the oil from draining back into the pan. The big hole (arrow 2) carries dirty oil to the filter.

 

When the engine was back in the car, I sprayed some brake cleaner on the check valve to remove any grit or debris. Still, it's a good idea to keep this covered.

 

A simple way to prevent problems is to stuff a paper towel or clean rag in the oil filter adapter bore.

Plugging hole for oil filter adapter.
 

 

Flex-Hone or ball hone for creating scratch pattern in cylinder walls when replacing piston rings.

This is a 4-1/8" Flex-Hone, or ball hone.

When used with an electric drill, this tool is used to create a diamond-shaped scratch pattern on the cylinder walls. The proper scratch pattern is necessary when new piston rings are installed, so the rings "seat" themselves properly. The scratch pattern helps the cylinder wall retain oil so the rings are always lubricated properly.

 

 

I applied some 10W-30 motor oil to the Flex-Hone WHILE SPINNING. The hone must be lubricated before using it in each cylinder.

To apply the oil, I rigged up a squirt bottle from an empty bottle of Lucas Oil Stabilizer. First I cleaned out the Lucas residue with paint thinner, then I blew out the liquid with compressed air. Next I sprayed some carburator cleaner into the bottle, swished it around, and poured it out. I blew the bottle out again and it was clean. I cut a tiny hole in the squirt tip of the Lucas bottle and poured in a quart of 10W-30 motor oil.

Applying oil to Flex Hone before honing cylinders.
 

While the Flex-Hone can be chucked into any 3/8" electric drill, many smaller drills spin at 1200 RPM or more, which is too fast for this procedure. I used a heavy-duty 1/2" drill motor that has a maximum speed of 850 RPM.

 

Flex-Honing The Cylinders:
Flex-honing the cylinders of a GM 4.3 liter V6 engine.

I started the drill and plunged the Flex-Hone into the cylinder.

I ran the brush up and down about once per second while spinning at full speed (850 RPM for this drill). Stroking up and down once per second means moving your arms really fast.

Caution: This procedure sprays oil around the work area and can make quite a mess.

 

 

 

Running this tool properly, and getting the proper angle, is kinda tricky. You are only supposed to run the flex hone for about a minute per cylinder, so you can't exactly practice very much on a good engine.

 

I can tell the angle of the scratch pattern by the angle of the swirls in the oil on the cylinder wall.

Scratch pattern left on cylinder walls after honing with ball hone.
 

 

Small patch of rust on cylinder wall.

After I wiped off the oil with a paper towel and carb cleaner, I noticed that cylinder 6 still had some black raised spots.

These spots formed a ring around the cylinder, which makes me believe they are rust spots from the engine sitting in my garage so long.

You may recall that the top ring on number 6 piston was rusted and stuck in the groove.

 

 

I bought this rigid hone for about $35.

I placed this in the drill motor and ran the hone up and down in the cylinder for about a minute. I applied oil to the stones and the cylinder wall before honing. This hone removed some, but not all, of the raised black spots.

I guess I will have to take my chances with some slight raised spots, because getting the engine bored out is too expensive for the value of the vehicle.

Rigid hone used to remove rust on cylinder wall.
 

 

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Cleaning The Engine Block Deck:

The mating surfaces between the engine block and cylinder heads must be clean and free of residue from the old gaskets.

Then there is the issue of surface smoothness. If you ever read a book on engine rebuilding, you will discover that the smoothness of the mating surfaces between the engine block and cylinder heads can be a HUGE issue. This is especially true with aluminum cylinder heads, which expand more than cast iron and need to slide laterally as they heat up.

3M Roloc Bristle Disc used to clean surfaces on engine.

This is a 3M Roloc Bristle Disc, which I bought at a local auto body supply store for about 10 bucks.

The yellow disc has 80 grit abrasive embedded in the plastic. There is also a green disc (50 grit) and a white disc (120 grit). These devices are used with a Roloc adapter (which also holds the conventional Scotch-Brite abrasive discs) in a die grinder that accepts a 1/4" shaft. This tool could also be used in a drill, but the RPMs are probably too slow for most people.

 

 

I used the Roloc Bristle Disc to clean the rubbery gunk from the "deck" of the engine block.

Cleaning old gasket residue from engine with Bristle Disc.
 

 

Sanding engine block deck with electric sander.

I used a random orbital sander with 220 grit sandpaper to remove the scratches from the engine block deck.

 

 

Note the pattern of tiny grooves from the original deck machining process.

My reasoning is that if the polymer-coated head gasket can seal up these grooves, then my small scratches should be no problem to seal.

Scratches on engine block deck from original manufacturing processes.
 

 

Sanding engine block deck with 320 grit sandpaper.

Finally, I sanded the deck with an orbital sander with 320 grit sandpaper.

I couldn't notice any difference when I sanded with this grade of sandpaper.

I used this orbital sander because I could not find Velcro-backed sandpaper discs finer than 220 grit. Adhesive-backed sanding discs are available up to 320 or 400 grit, and are used in the auto body trade with pneumatic sanders. But I didn't want to buy such a tool just for this job.

 

 

Cleaning The Head Bolt Holes:

I ran a 3/8 inch brass bottle brush through each bolt hole (red arrow).

I snipped off the loop handle on the end of the brush and chucked it in my cordless drill. This worked well.

Cleaning head bolt holes with small bottle brush in drill.
 

At this point it would be a good idea to "chase" all the head bolt holes with a tap. These holes have a 7/16" - 14 thread. I did this procedure later, just before installing the cylinder heads.

 

Washing The Engine Block:

Honing the cylinders liberates A LOT of very abrasive grit from the ball hone and deposits that debris on the cylinder walls and possibly the lower crankcase.

Removing this debris completely is VERY IMPORTANT, or the rebuilt engine may develop scoring on the cylinder walls or some other type of dirt-related failure.

While it's tempting to use solvents (e.g. mineral spirits, carb cleaner, brake cleaner) to remove the grit-impregnated oil from the cylinders, the best method is to use regular laundry detergent and hot water. Just mix it extra strong.

 

Plastic taped over valley in engine block to keep water out during washing.

To keep water out of the lifter valley, I taped a sheet of plastic over the valley.

I also installed the old timing chain cover to keep water away from the timing gear area.

 

 

Cleaning Debris From The Block:

I mixed two cups of laundry detergent with two gallons of very hot water and poured some liquid into a small garden sprayer.

I sprayed the detergent into the cylinders...

Spraying laundry detergent and water in cylinders to remove grit from honing.
 

 

 
 
 
 
 
 
 
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Scrubbing cylinder walls with brush.

...and scrubbed them with a dishwashing brush.

Don't expect to see much suds. Laundry detergent doesn't make a lot of suds.

 

 

I also sprayed some detergent into the cooling passageways and scrubbed them with an old toothbrush.

Spraying detergent into cooling passages.
 

 

I sprayed more detergent into the cooling passageways and then I rinsed the cylinders and deck with a garden hose. I sprayed water into each hole in the deck and quite a bit of dirty water came out of the other holes. I tipped the engine block over so the deck was facing down and ran water into the water pump opening (on the front of the block) for a minute.

Then I blew off as much water as possible with compressed air and a blow gun. I wiped off any visible water with paper towels. At this point I began noticing rusty streaks forming, so I applied some motor oil to a paper towel and wiped the cylinders with oil, as well as the deck. I needed to keep the bare iron deck surfaces oiled while the engine block dried. Before installing the cylinder heads, I can remove the oil with brake parts cleaner.

I set up a large fan to blow air on the engine block to dry up any remaining water.


Next Page: Part 5 - Installing The New Crankshaft

Previous Page: Part 3 - Crank Removal

More Info:
Tools Used:
  • Ball Hone (Flex Hone) 4.25" Diameter
  • Rigid Hone
  • Heavy Duty Electric Drill
  • 3M Roloc Bristle Disc, Medium (80) Grit
  • Angle Die Grinder
  • Electric Sander (Optional)
  • Dishwashing Brushes
  • Garden Hose
Materials Used:
  • Motor Oil
  • Plastic Sheet
  • Paper Towels
  • Sandpaper: 220 grit, 320 grit
  • Laundry Detergent
 
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