Can I do this?

[johnsob3]

Hello:

I am swapping out a standard 6.9 1986 engine. I am replacing it with a 7.3 1989 engine.

Can I use the same flywheel and transmission that was used on my 6.9?

Regards

[cdnsarguy]

The recent thread on which is better (6.9 or 7.3) got me to reading this book I borrowed from Bob at the IDI Weekend, and it turns out there are a lot of subtle differences between the two beasts. I figured there needs to be a deffinitive list, so here it is.
First year for the 6.9 - 1983
Last year for the 6.9 - 1987
By 1988 all production 7.3
6.9 - Max H.P. 175 Torque 318 ft. lb.
7.3 - Max H.P. 185 Torque 338 ft. lb.
6.9 max torque at 1800 RPM
7.3 max torque at 1600 RPM
Both max HP at 3300 RPM.
7.3 external identification variance from 6.9 - New fuel filter/fuel heater/water sparator, larger/taller cylinder head bolt bosses with ribs. Dual mass flywheel on 5spd.
Crankcase differences
Cylinder bore - 6.9 = 4.00"
Cylinder bore - 7.3 = 4.11"
Stroke for both - 4.18"
Top deck thickness - 6.9 = .500"
Top deck thickness - 7.3 = .560"
Oil drain Back holes - 6.9 = 3/8"
Oil drain Back holes - 7.3 = 7/16"
Cylinder head changes
Cylinder head bolts - 6.9 = 7/16"-14 UNC 5.25" long
Cylinder head bolts - 7.3 = 1/2" - 13 UNC 6" long
Cylinder head bolt washer 6.9 = .105" thick
Cylinder head bolt washer 7.3 = .134" thick
Head bolt torque -
6.9 with new bolts = 75ft. lbs.
6.9 with used bolts = 85ft. lbs.
7.3 new or used = 100ft. lbs.
Cylinder head gasket changes -
Fire ring I.D. 6.9 = 4.14"
Fire ring I.D. 7.3 = 4.22"
Gasket cutouts elimitated between cylinders on the 7.3 to eliminate cosmetic corrosion phenomenon.
Viton oil drain back sealing rings added to the 7.3 (also used in later versions of the 6.9 head gasket, then eliminated again).
Head design changes -
6.9 features "centered" glow plugs, while 7.3 are "off-center"
Injection nozzles have been retracted on the 7.3 .060" to facilitate Federal and state emission certs.
Precombustion chamber volume -
6.9 = 18.34 cm3
7.3 = 20.42 cm3 (increased only for emissions certs)
Precombusion chamber inserts are physically interchangable, however the throat has been redesigned to distinguish them apart, and the 7.3 prechamber cup has an embossed "88" on it.
Valve Stem -
The 7.3 valve stem oil sheild is larger to reduce hydrocarbon emissions. Intake and Exhaust sheilds have been color coded, even though they are identical and interchangeable.
Coolant passages -
The lower corner coolant passages on the cylinder head on the 7.3 have been plugged. This change is introduced to eliminate lower corner gasket coolant seepage during cold start engine warm-up. Mating passages in the block are also plugged. (could be why we hear more 7.3 overheating issues).
Exhaust valves - The 7.3 exhaust valve has had its alloy composition changed, with more nickel, chrome, and silver content, and decreased manganese content. The 7.3 valves may be used in the 6.9, but not the other way around.
Piston and ring sizes increased in accordance with bore changes. The 7.3 utilizes select fit pistons at the manufacturer. The engine is produced with A,B,C and D size pistons and cylinder bores. When re-using pistons, "A" pistons should go in "A" cylinders, and "B" pistons in "B" cylinders and so on. These letters are stamped on the pistons and the cylinder bores at the bottom of the bore when viewed from the crankshaft side. Service part pistons can be utilized in any bore, and are identified with an "S".
Flywheel -
IMPORTANT. DO NOT USE 6.9 flywheel or vibration damper on 7.3 or vice versa. If components are intermixed, engine vibration and premature component wear may be encountered. For identification, compare these part numbers.
Vibration damper 6.9 1805414C1
Vibration damper 7.3 1809117C1
Flywheel Auto 6.9 1803219C1
Flywheel Auto 7.3 1809212C1
Flywheel manual 6.9 E7TA-6477-AB
Flywheel manual 7.3 E8TA-6477-AA
Injection Pump - Changes have been made to increase fuel flow and change ignition timing on the 7.3. Low and High altitute calibrations are available for both.
6.9 High - 1807568C91
6.9 Std. - 1807560C91
7.3 High - 1809045C91
7.3 Std. - 1809121C91
Injection lines - Due to the .060" retraction of the injector nozzle on the 7.3, all 7.3 injector lines have been shortened by .060" However, all lines with the exception of #1 on F series, and #4 on E series, are interchangeable between 6.9 and 7.3.
Cylinder wall honing -
Plateau cylinder wall honing has been implimented on the 7.3 to promote ring seating and engine break-in.
Front cover -
The 7.3 features an embossed front cover to improve sealing and eliminate water pump replacement due to gasket seepage.
All this stuff came out of the 1987 7.3L diesel engine technician's update, which was used to quickly bring up to speed a 6.9 diesel mechanic. Also inside, was a chart which I found interesting. It shows the amount of HP required for a given frontal area at a given speed. I don't want to type up the whole chart, but I'll give you one column, for 55 MPH
Area in Sq. Ft. - HP required
50 - 56
60 - 66
70 - 78
80 - 89
90 - 99

That should be of interest to those of you with campers. - Mel

[johnsob3]

Thanks for the reply...very nice!

The flywheel refrence mad in your post warns about swapping flywheels. Is this due to the dmfw in the 7.3? Is there going to be a sinificant difference to prohibit the use of the 6.9 solid flywheel and 4 speed standard transmission?
What would be damaged, engine or transmission?

[cdnsarguy]

Don't think the 4speed bell housing will bolt to the 7.3 trans adapter plate......... anyone know for sure out there....

[johnsob3]

The transmission and flywheel all bolt up perfectly. They even use the same starter.
I have checked on line to get the flywheel clutch kit for the 7.3 but in 1989 they used a 5 speed manual trans and the input shaft spline went from 1 1/16 to 1 1/4 on the 7.3. So the kit for the 7.3 will not mate with the 6.9 transmission input shaft. That is why I wanted to used the 6.9 flywheel and drive line.

[suv7734]

Originally Posted by johnsob3

The transmission and flywheel all bolt up perfectly. They even use the same starter.
I have checked on line to get the flywheel clutch kit for the 7.3 but in 1989 they used a 5 speed manual trans and the input shaft spline went from 1 1/16 to 1 1/4 on the 7.3. So the kit for the 7.3 will not mate with the 6.9 transmission input shaft. That is why I wanted to used the 6.9 flywheel and drive line.

Using a 6.9 clutch disc and pressure plate will not make a difference since they are not balanced 'to the engine'. The important piece is the flywheel which is balanced to the engine. As long as the pressure plate and disc will fit the 7.3 flywheel you will be good to go since the clutch disc has the splines that mate with the input shaft.

[johnsob3]

The issue is all of my parts, flywheel, clutch, transmission are from the 6.9. What I get from suv7734 is my flywheel will not be balanced for the 7.3. Will this be the case for sure?
Sorry to be a pain on this because finding the right combination may be troublesome.

Regards, Johnsob3