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Rebuilding International’s 7.3L IDI Engine

Project 300 Part 10: Honing Cylinders

Text By Jason Thompson, Photography by Jason Thompson

We bought Project 300 (an ’87 Ford F-250) more than 2 years ago for $300. Right now, the truck is sitting in the street, waiting for its International 6.9L IDI diesel engine to be replaced with an updated 7.3L IDI version (currently on an engine stand in the garage). Before we bought the truck, it had been out of service for a number of years, and the engine only made about 60 percent of its rated power on the dyno.

We figured the engine would die at some point, but we didn’t know the exact date. In the meantime, we added an ATS turbo, Snow Performance water injection, and a Dieselcraft oil centrifuge—which we plan to swap over to the new engine. We didn’t want to put money into the 6.9L because we got the 7.3L cheap.

How An Old Engine Dies
We were interested to see what would go first, the 6.9L’s head gaskets or the piston rings. Both were in bad shape, but the rings claimed the bittersweet victory in the end. Although, not before the truck made it to the United States-Mexican border (and back) with the new engine in the bed—a very noble effort.

The Key To A Cheap (But Good) Rebuild
In 1972, Brush Research Manufacturing (BRM) introduced the Flex-Hone, which is also affectionately known by diesel technicians as the dingleberry hone, bead brush, or glaze breaker. This tool is said to be self-aligning to the bore and self-compensating for wear because of its design, which is made of floating, abrasive globules on high-density, nylon filaments. Once the procedure is completed, you’re left with a plateaued surface, since the peaks and imperfections are cleanly removed. This creates a non-directional or crosshatched cylinder that contains microscopic valleys for oil retention. We ordered the Flex-Hone brush so we could freshen up our 7.3L’s cylinders and get them ready for the new piston rings. Follow along, and we’ll show you what we did.

Part 10: Honing the Cylinders
Flex-Hone 41⁄8-inch (105MM) 320-grit Silicon Carbide (PN GB41832) $65.80
Summit Racing 2,000-pound engine stand (PN SUM-918010) $124.95
Machine shop labor on heads and crankshaft $340
Total Stage 10: $530.75
Project 300 total to date : $10,636.75

Price List: Stage 1 to 9
Truck purchase price, glow plugs, fuel return lines, dyno testing, ATS Aurora 2000 wastegated turbo, ATS exhaust, body mounts, tires, spray paint, bearings, brakes, leveling kit, block heater, radiators, heater core, oil centrifuge, Sulastic springs, rear antilock brake valve, Pioneer CD player and speakers, Snow Performance water-methanol injection, LMC Truck bumpers, and alternator Total: $10,106

SOURCES
Summit Racing
Akron
OH
800-230-3030
330-630-0240
www.summitracing.com/
By Jason Thompson
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