6.9 or 7.3
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New User
Joined: Aug 2012
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6.9 or 7.3
First post on this site, but this is my second diesel. I have a 99 cummins and now this 93 c&c 4x4, 4.10 ls with factory turbo, 5 speed the engine is dusted.....all the cylinders measure greater than .015 over and are slapping the cylinder walls. I have found a 87 6.9 reman with 50,000 miles. Most of it's life was farm use. I also found a 89 7.3 non turbo with 120,000 owner stated SCA's where used... I will test , owner religious on maintenance, installed new injectors and return lines a month ago, along with single mass fliywheel last year..
I have a 093 factory ford turbo with ats upgraded exhaust housing. This will be installed.
this will not be a daily drive, and will pull about 14,000 pounds, and plan to install hoist under the flatbed, hay hauler, farm use etc....
The million dollar question..... what engine do I get, both engines are the same price, witnessed both running the 7.3 is about an hour farther away.
I am not looking for wild power i have the cummins for that..... I want reliability and work all day power.
thanks
for the help
I have a 093 factory ford turbo with ats upgraded exhaust housing. This will be installed.
this will not be a daily drive, and will pull about 14,000 pounds, and plan to install hoist under the flatbed, hay hauler, farm use etc....
The million dollar question..... what engine do I get, both engines are the same price, witnessed both running the 7.3 is about an hour farther away.
I am not looking for wild power i have the cummins for that..... I want reliability and work all day power.
thanks
for the help
Senior User
Joined: Aug 2012
Posts: 218
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From: Ft. Worth
What Motor?
This is just my opinion...If you really want nothing more than a slow workhorse that can take the abuse...stick with the 87 6.9...That is probably one of the best years for that block...super easy to work on...The 7.3 is missing some "meat" which was carved out of a 6.9...Don't get me wrong...the 7.3 can be a good engine, but in my mind takes a lot more maintenance to maintain...
Besides that...you can put true (and I wouldn't go bigger) 2 1/2" duals...with or without mufflers...on her...Then drill 1 1/2" to 2" holes on the outside of the air filter housing equally spaced all around...tune her up with IP and injectors...put a zf-5 behind her and there you go...
A good solid everyday workhorse engine...without all the extra expensive parts...
Just saying and just my opinion...
BeerCan500
Besides that...you can put true (and I wouldn't go bigger) 2 1/2" duals...with or without mufflers...on her...Then drill 1 1/2" to 2" holes on the outside of the air filter housing equally spaced all around...tune her up with IP and injectors...put a zf-5 behind her and there you go...
A good solid everyday workhorse engine...without all the extra expensive parts...
Just saying and just my opinion...
BeerCan500
i ain't rite
Joined: Mar 2005
Posts: 65,507
Likes: 5,563
From: Marlboro Mental Hospital.
i would go with the 7.3
120k is nothing, and it has not been opened.
i am always leery about a "reman" engine, because you have no idea what was done or what was not done to it.
i have seen many many engines that were "rebuilt" or "reman" that only had the one connecting rod that broke replaced, or the one piston and one valve that fell into the piston replaced.
120k is nothing, and it has not been opened.
i am always leery about a "reman" engine, because you have no idea what was done or what was not done to it.
i have seen many many engines that were "rebuilt" or "reman" that only had the one connecting rod that broke replaced, or the one piston and one valve that fell into the piston replaced.
Postmaster
Joined: Aug 2010
Posts: 2,554
Likes: 7
From: Northern Arizona
Unless the 6.9 happens to be one of the 87's outfitted with the ZF you are going to have to get the right clutch and pressure plate to work with a 6.9 flywheel... and a flywheel if the 6.9 happens to be an auto. You can't use your 7.3 clutch set-up. Apologies if you knew this already and were considering it, but it might be an unforeseen expense if you were thinking you could use your 7.3L flywheel and clutch on the 6.9L.
If the SCA's were indeed maintained I would personally lean toward the 7.3 with 120K over a reman as well... provided it really IS only 120K, not 220K or 320K... yikes! Boils down to the trustworthiness of the seller. 50K on a rebuild is perhaps even harder to verify. I would want to see some kind of receipt trail that describes in detail what was done and which parts are new, and a way to verify the seller's mileage claim (mileage documented on receipts jive with current mileage minus 50K...)
In both cases I would be curious as to why the seller was parting out the engine like that. Why would someone put a bunch of new parts into an engine and then turn around and pull the engine and sell it? Makes it very hard to get any additional value out of the truck except as scrap. BE CAREFUL!!! Low mileage used engines are suspicious to me unless it's coming from a wrecked truck or similar. Might we ask what the prices of these engines are?
If the SCA's were indeed maintained I would personally lean toward the 7.3 with 120K over a reman as well... provided it really IS only 120K, not 220K or 320K... yikes! Boils down to the trustworthiness of the seller. 50K on a rebuild is perhaps even harder to verify. I would want to see some kind of receipt trail that describes in detail what was done and which parts are new, and a way to verify the seller's mileage claim (mileage documented on receipts jive with current mileage minus 50K...)
In both cases I would be curious as to why the seller was parting out the engine like that. Why would someone put a bunch of new parts into an engine and then turn around and pull the engine and sell it? Makes it very hard to get any additional value out of the truck except as scrap. BE CAREFUL!!! Low mileage used engines are suspicious to me unless it's coming from a wrecked truck or similar. Might we ask what the prices of these engines are?
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New User
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The 6.9 I believe is the new block casting for the 6.9, it is fitted with a c6 tranny. I had planned to buy a LUK lfw127 and use the 12" clutch and pressure place from my 93 IDIT on the 6.9. The 6.9 was installed 5 years ago and was farm duty, so the body is beat to he!!....the owner selling the 6.9 is the second owner and he bought it for the dana 60 to put under his 97 f250 to get rid of the d50. No ducmentation on the miles...engine is very clean no oil leaks and if you wipe the dust off the gray paint is quite shiny....
but he has had it a year and half and has been sitting during this time and started to keep things lubicrated. price 400.00
The 7.3 is out of an 1989 f350, original owner, and was parted out because the body was rusted out badly, new tranfer case, year old smf clutch kit, new injectors and return lines in the last month, oil changed every 3000 miles, no oil leaks, not as clean as the 6.9. price 400.00
I am leaning towards the 7.3 with 120,000 unopened, I don't like remans unless I do it, then I know what was done...my idea of a rebuild and somebody elses is completely different...
thanks for the posts....keep them coming I am going to get one of them tonight.
but he has had it a year and half and has been sitting during this time and started to keep things lubicrated. price 400.00The 7.3 is out of an 1989 f350, original owner, and was parted out because the body was rusted out badly, new tranfer case, year old smf clutch kit, new injectors and return lines in the last month, oil changed every 3000 miles, no oil leaks, not as clean as the 6.9. price 400.00
I am leaning towards the 7.3 with 120,000 unopened, I don't like remans unless I do it, then I know what was done...my idea of a rebuild and somebody elses is completely different...
thanks for the posts....keep them coming I am going to get one of them tonight.
Elder User
Joined: Feb 2012
Posts: 888
Likes: 2
Unless the 6.9 happens to be one of the 87's outfitted with the ZF you are going to have to get the right clutch and pressure plate to work with a 6.9 flywheel... and a flywheel if the 6.9 happens to be an auto. You can't use your 7.3 clutch set-up. Apologies if you knew this already and were considering it, but it might be an unforeseen expense if you were thinking you could use your 7.3L flywheel and clutch on the 6.9L.
all 6.9/7.3 N/A flywheels are interchangeable.
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Fleet Owner
Joined: Jul 2006
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From: Mi'kma'ki
just because people "let it slide" with proper coolant maintenance for the 6.9l,doesn't make it right.all high compression engines require proper sca's for normal coolant.the 6.9l isn't exempt.The walls are still being attached without sca's,it's just their thicker,so getting pin holes isn't common.
i have read of a 6.9l suffering from cavitation as well.it can happen.
both engines require the exact same maintenance schedule.
id go for the 7.3l.there's no replacement for displacement.
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Post Fiend
Joined: Feb 2009
Posts: 8,005
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From: Ottawa, Ontario
Since you want a farm use workhorse, and towing heavy, I'd take the 6.9 for 1 easy reason, the 6.9 has a big opened coolant port in the heads, that were blocked off in 7.3's.
And reading over the years on the forum, stuck in heavy traffic pulling a trailer, with A/C blasting a 7.3 will get hot.
And I put my 6.9 thru everything heat/work wise, and it's hard to keep it over 200*!
And reading over the years on the forum, stuck in heavy traffic pulling a trailer, with A/C blasting a 7.3 will get hot.
And I put my 6.9 thru everything heat/work wise, and it's hard to keep it over 200*!
Postmaster
Joined: Aug 2010
Posts: 2,554
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From: Northern Arizona
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I know that the IDI and IDIT flywheels can not be swapped.
I made the trip and picked up the 7.3 last night. The clean up begins tonight.
I have new valve cover gaskets, new rear main seal ready to go on, and drop this in on sunday....I hope.
The clutch, pressure plate and SMF flywheel is only a few months old and looks like a 11 inch clutch. The Manufacurer is AP, any opinion on this? ever heard of them? can I use the oem trow out?
I made the trip and picked up the 7.3 last night. The clean up begins tonight.
I have new valve cover gaskets, new rear main seal ready to go on, and drop this in on sunday....I hope.
The clutch, pressure plate and SMF flywheel is only a few months old and looks like a 11 inch clutch. The Manufacurer is AP, any opinion on this? ever heard of them? can I use the oem trow out?
i ain't rite
Joined: Mar 2005
Posts: 65,507
Likes: 5,563
From: Marlboro Mental Hospital.
you can use a 7.3 clutch setup on a 6.9 and a 6.9 on a 7.3
but you have to use it all . no mix and match. because the 6.9 used a one piece flywheel and the 7.3 used a dual mass flywheel.
the only thing a 6.9 solid flywheel setup on a 7.3 will do is give you some gear rollover noise out of the 5 speed trans.
but you have to use it all . no mix and match. because the 6.9 used a one piece flywheel and the 7.3 used a dual mass flywheel.
the only thing a 6.9 solid flywheel setup on a 7.3 will do is give you some gear rollover noise out of the 5 speed trans.
Postmaster
Joined: Aug 2010
Posts: 2,554
Likes: 7
From: Northern Arizona
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
Timing gear has 106 teeth........
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
Timing gear has 106 teeth........