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How to Swap A 460 Big Block Into A Ford 6.9L Diesel Pickup

Swapping a 429-460 Ford V-8 in a F-250 with a Navistar 6.9L diesel

Ford's seventh-generation F-series pickups comprise model years 1980 through 1986. 1982 to 1986 appear externally similar, and 460 big-block gas and 6.9L International Harvester IDI engines were optional in the F-250 HD/F-350 pickups starting in 1983. But that doesn't mean the big 460 won't fit in the lighter-duty F-150 like the red and white half-ton shown in the lead photo—or any other Ford pickup or fullsize Econoline van, for that matter. Bill Schwarz from Florence, Oregon, wrote us with the following question about swapping a gas engine in place of his '85 Ford F-250's 6.9L Navistar diesel.

"I have a low-mileage, showroom-condition, 1985 Ford F-250 two-wheel-drive pickup that has water in the oil and has been diagnosed as DOA. It has been sitting in a garage since 1990. The engine is a 6.9L diesel that I would like to replace with a gasoline engine. Do you have a suggestion that will bolt up to the four-speed manual transmission?

I would like to go simple—carburetor, distributor—just a good old engine that I can install and work on and keep running. The truck would be a fun driver, so it does not have to be a workhorse hauler or pull trailers, etc."

Possible Ford engine choices to replace the original International Harvester-built 6.9L diesel engine in an 1985 Ford F-250 pickup include Ford's 300 inline six-cylinder (boring!), the 302/351W small-block Ford V-8, or the 429/460 "385"-series big-block Ford V-8. All except the earlier 429 were stock options in 1985. In our opinion, for the heavy three-quarter-ton F-250, the 460 is the preferred choice, whether for work or for play. A 460 stocker makes an S-load more power and torque than the early 6.9L diesel, yet even though it's a big-block, the 460 is still about 250 pounds lighter than the 6.9L—so that's what we'll be discussing in detail here. Nevertheless, for any of these engine series there are differences in engine mounts and frame perches, the front crossmembers, and the bellhousing/rear engine-face bolt-pattern compared to the unique diesel.

Mark Sanchez/AEWTake out 429 Ford with C6 trans waiting to go into its new home.

The "385-series" 429/460 big-blocks are a popular swap candidate with Ford traditionalists. In Southern California, you can still buy one of them with transmission complete from fan to tailhousing, air cleaner to oil pan for under $1,000 at the local pick-your-part wrecking yard. Engines by themselves range from $400 to $600.

The Shadetree Budget Approach

Go to the wrecking yard, find a 1984-1986 Ford pickup or similar vintage Ford truck, and just pull the entire engine and transmission "module" of your choice out of the same vehicle (including clutch assembly if a manual, or torque converter if an automatic). This provides surety the entire drivetrain is compatible, provided the transmission comes out of a vehicle with the same drive system as yours (two-wheel or four-wheel drive).

Don't forget to grab everything that attaches to the motor, including the stock engine mounts (rubbers as well as frame perches), front-end accessories and accessory drives, transmission crossmember and mount, and (if the donor has the same wheelbase as your receiver truck) the driveshaft as well. Be prepared for driveshaft and transmission yoke modifications if the wheelbase or trans is different than the original.

One thing to watch out for is possible front No. 2 crossmember variations. On a factory Ford 460 installation, the crossmember has a taper that provides clearance for removing and replacing the oil filter—easily accommodated on non-tapered crossmembers by using a remote oil filter kit (see "Oiling" below). On diesel engine applications, existing rivets in the diesel-specific crossmember require removal to clear stock Ford 460 frame perches. Although Ford welds the entire crossmember to the framerails, reportedly removing the rivets may cause the frame to "spread." But there is a one-stop aftermarket solution for this.

The Aftermarket Kit Approach

L&L Products specializes in complete 429/460 Ford big-block engine conversion kits for just about every year and model fullsize Ford truck and Bronco—two- or four-wheel drive. Its bolt-in-place frame perches don't require rivet removal and bolt to pre-existing bolt holes. The entire engine module installs in such a way that you don't have to change the transmission crossmember or move it around in the vehicle. Your existing transmission will end up sitting exactly in the same place. As L&L owner Alan Lundquist puts it, "We don't hurt the integrity of the truck." L&L's complete Kit No. 5 works for your 1985 diesel-to-460-gas swap.

L&L Kit No. 5 converts any two-wheel-drive, 1984-1996 fullsize Ford truck or Bronco with a 300ci straight 6 or 6.9L V-8 and a manual trans (including the T18, T19, SROD, and NP435) to a 429/460 big-block gas engine. For a C6 automatic conversion, use L&L Kit No. 3 (crossmember and driveshaft mods may be necessary if changing from stick to automatic or vice versa). Most parts are available individually if you don't need every part shown in the complete kit. Kits are also available for wheel-drive versions.

Diesel Trans to 460 Engine

For those of you who have a C6 automatic behind the diesel, it's really just a 429/460-pattern case; throw away the factory-installed trans-to-diesel engine block adaptor plate, get a 460 Ford separator plate, and bolt everything directly up to the 460 using a 460-pattern auto trans flexplate with the right torque-converter mounting pattern. Easy peasy. For a small-block Ford, you'll need an aftermarket transmission adapter plate to bolt up the big-block-style C6 case—or find a small-block C6 transmission.

With a manual transmission, the situation's a little iffier. You can retain the 6.9L diesel's T-18/T-19 manual tranny behind the new 460 engine, but—again due to rear block-face bolt pattern differences—this requires a 460-type bellhousing. In production, Ford also used an adaptor plate that mates the 6.9L diesel to a 460-like bellhousing casting that in turn mounts to the transmission. The internet is rife with comments that by removing the adapter plate, the diesel bellhousing bolts directly to a 460 gas engine (just like the C6 transmission case does). However, though at first glance the bellhousing castings for each motor appear identical, they had different Ford OE part numbers, and some reputable sources maintain there's a chance that not all mounting holes needed for the 460 are drilled through on the diesel version. You can verify hole locations by matching up the existing bell with the correct 460 separator plate, which conceivably could serve as a template for adding the "missing" holes. The most critical hole locations are of course for the dowel pins. They must be dead nuts on for proper transmission alignment, which is critical for manual transmission longevity, crisp gearshifts, and reliable clutch release. Be prepared to use aftermarket adjustable-offset dowel pins and dial-indicate the entire assembly. For the average shade-tree mechanic, it is probably safer (but admittedly much costlier) to locate a "correct" 460 bellhousing.

What is the right bell? The "correct" stock 460 bellhousing must be large enough to fit the huge stock 12-inch clutch assembly and 184-tooth flywheel. It also must accommodate the Ford truck manual transmission's larger trans pilot-collar diameter, which means the rare factory 1970-1971 429 Mustang bellhousings or even the 351M bellhousings won't cut it (unless you use a smaller aftermarket flywheel and clutch, not recommended on a heavyweight F-250 -ton truck). For the big stuff, the bell must come from a 460-equipped F-series truck. On a mechanical clutch setup, use the bell out of a 460/four-speed 1972-1979 F-series truck; for a hydraulic clutch with an OE-style slave cylinder use 1983-1991 460 truck bellhousings. Use a 460 starter, not the diesel starter. Install a 460 or diesel slave cylinder, which is larger than a 351 or 302 slave.

Quick Time's RM-8011 bellhousing has multiple transmission bolt patterns and pilot-hole ring inserts that allow it to accept most Ford and GM transmissions (including Schwarz's T-19) to 429/460 engine blocks. It has no external slave cylinder provisions; instead, use an aftermarket integral hydraulic release bearing assembly, available from Quick Time and others. About $735 at Amazon.com.

Can't find the right factory bell? Go aftermarket: Quick Time by Holley bellhousing (PN RM-8011) is one solution. The multi-pattern bell has three different trans-to-bellhousing mounting patterns and can accommodate (via supplied ring inserts) four different transmission pilot collar diameters, allowing use with Ford passenger-car, Ford truck, T5, and GM transmissions (as well as their aftermarket descendants and clones). Depth-wise, it basically accommodates those transmissions with about a 6.5-in-long input shaft; diameter wise, it can take the large truck 460 flywheel and clutch.

Flywheel and Clutch

Inside the bellhousing you'll need a 460 flywheel and compatible clutch. In terms of stock replacement, the diesel and 460 pressure plates are identical, but the clutch disc is different. You'll probably want to use aftermarket performance parts for strength and longevity anyway. All 429 and 1978 and earlier 460 engines were neutral balanced; the 1979 and later 460 is externally balanced. Flywheels must correspond.

Specifically designed for truck and Bronco applications, L&L's 429/460 heavy-duty clutch and flywheel assembly include a 40-lb, NHRA-approved, billet steel flywheel; a heavy-duty pressure plate and clutch disc; a roller pilot bearing; and mounting hardware. PN 04385A includes a neutral balanced flywheel for 1978 and older 429/460 engines; PN 04385S has a flywheel with 28 oz-in unbalance for 1979 and newer 460 engines.

Cooling

You can retain the huge diesel radiator with the 460. Its inlets and outlets are on the correct sides. L&L offers its own "Super Cooling" radiators for these conversions. You will need a 460 mechanical fan and fan shroud. If you can't find a 460 fan shroud, you can modify or trim an existing diesel or small-block shroud. With a mechanical fan, about one third of the fan blade should protrude out of the shroud.

Oiling

Use a 460 truck rear-sump oil pan and corresponding rear-sump oil pump and pickup-and-screen assembly. Hopefully, they'll already be on the donor engine. If not, one aftermarket solution for 1980 and newer Ford trucks and Broncos is L&L's baffled 7-quart (with filter) oil pan kit (PN 040500), which also includes a high-volume pump, a main-cap oil pickup tube support stud, an oil pump drive rod, high-volume pickup screen-to-pump gasket, pickup screen-to-oil pump bolts, and a dipstick-and-tube assembly. If the oil filter won't clear the No. 2 (front) crossmember, use L&L's 90-degree remote oil filter system (PN 040183).

Ford trucks and Broncos need a rear sump oil pan. Ford Performance Parts' 460 six-quart (with filter) engine-swap oil pan includes the right oil pan, plus the proper dipstick and tube, pickup tube and screen, one-piece oil pan gasket, and main cap pickup tube retention stud. On some early 429/460 blocks, it may be necessary to drill out the four pan and pan gasket corner bolt holes to -inch. This pan kit also works for swapping the 429/460 into 1979-1995 Mustangs and other Fox-chassis cars. $165.99 at Summit Racing.

Front Drives

Use the front drives and brackets from a 460 truck. The diesel power steering pump is the same as a 460; other accessories including the alternator and air conditioning may differ. 460 poly-V belt-drives didn't arrive until 1987 —the same time period when 460s went to direct-port fuel injection. L&L offers conventional V-belt billet-aluminum pulleys and mounting brackets if needed. These include: PN 10156B alternator mount and drive kit; PN 10145C power steering mount and drive kit for the existing C-11 pump; and PN 010186 for mounting a late round-type FS6 A/C compressor.

Front accessory drive 460-swap brackets and V-belt pulleys are available from L&L. For example, this kit, PN 10145C, bolts the diesel's existing C-11 stock-type power steering pump to 1980 through 1988 trucks and Broncos running a 460.

Exhaust

Any 460 truck or Econoline van exhaust manifolds should work. L&L also offers headers for this swap. 460 headers from other sources may not always clear L&L's mount package.

For two- and four-wheel-drive 1980 to 1996 Broncos and F-series trucks without EFI, under PN 79760A L&L sells nickel-plated, "Ultra Flow," full-length chassis-exit headers with 1 -inch primaries that fit standard exhaust-port 429/460 heads (they won't fit Cobra Jet ports). Versions for EFI and/or air injection smog pump tubes are also available. This driver-side view also shows L&L's 460 engine mounts, remote oil filter adapter, and 7-quart rear-sump oil pan.

Electrical

No big deal if emissions compliance or fuel injection isn't in the picture. According to Ford expert Mark Sanchez (Advanced Engineering West) there are only two critical wires needed for basic gas engine operation: "Hot while cranking (red with a blue stripe in Ford's wire color-scheme); and hot in run, ignition on (red with a green stripe). The cranking wire runs to the starter solenoid, so that wire should be virtually identical on the diesel. Run the ignition wire directly to the gas motor's ignition coil."

Fuel system

Whether diesel or gas engine, several different fuel tank options were available. These include various single and dual tank configurations, locations, and capacities. Thoroughly purge the fuel tank and fuel lines of any residual diesel fuel and change the fuel filter to one recommended for gasoline. If any of the sending units incorporate an in-tank electric pump, replace it and the sending unit with the equivalent one for a 460. There's generally no need to replace any sending unit that doesn't incorporate a pump. Fuel lines up front may require rerouting and/or modification.

Sources

Advanced Engineering West (AEW); Mira Loma, CA; 626.222.4648; mailto:AEWperformance@AOL.com

Amazon.com Inc.; Seattle, WA; Amazon.com

Ford Performance Parts; Dearborn, MI; 800.FORD788 or 313.621.0771; https://PerformanceParts.Ford.com

L&L Products Inc. ; Rowlett, TX; 972.475.5202; LandLproducts.com

Quick Time, A Holley Performance Brand; Bowling Green, KY; 866.464.6553; Holley.com/brands/quick_time

Summit Racing Equipment; Akron, OH; 800.230.3030 (U.S.) or 330.630.3030 (outside U.S. ); SummitRacing.com