What is the quickest way to tell a 6.9 from a 7.3?

[87-F-250]

Differences:

6.9L uses a 7/16 head bolt.

7.3L uses a 1/2 head bolt.

What is the quickest way to tell by just looking at the two different engines?

 

[Agnem]

The head bolt size is the fool proof way. However, if you think your looking at a pretty unmolested truck, there are easier visual clues that will tell you real quick. It is usually the sum of these features more than any one individual feature.

All of the below screem 7.3!
Serp belt
Glow plug controller and bullet style GP's.
extra screw on the IP
gear tower oil fill
uncluttered passenger side wheel well cover
Engine harness connector on drivers side.

Basically a 6.9 is going to have the opposite of those
V belts
spade term glow plugs and disconnected GPC
plain IP
Oil fill bolted on the front of the gear tower
wires everywhere on the passenger side
no wires between engine and drivers side

 

[k_williams1982]

The head bolt size is the fool proof way. However, if you think your looking at a pretty unmolested truck, there are easier visual clues that will tell you real quick. It is usually the sum of these features more than any one individual feature.

All of the below screem 7.3!
Serp belt
Glow plug controller and bullet style GP's.
extra screw on the IP
gear tower oil fill
uncluttered passenger side wheel well cover
Engine harness connector on drivers side.

Basically a 6.9 is going to have the opposite of those
V belts
spade term glow plugs and disconnected GPC
plain IP
Oil fill bolted on the front of the gear tower
wires everywhere on the passenger side
no wires between engine and drivers side

My '88 F250 with a stock 7.3 (I replaced it with a 6.9) had V-belts, and all the wiring came off the passenger fender and over to the motor. It did have the bullet style GPs and the 7.3 style controller though.

 

[david85]

I think V belts started in 1992 along with many other cosmetic and structural tweaks to the OBS line.

1987 6.9s also had the bullet terminal glow plugs and they are backward compatible to older 6.9s. Its rare, but some 6.9s that originally came with the older glow plug system have been retrofitted with the newer solid state controls.

 

[Chevyboy_0]

My 87 has the bullet type GPs, solid state GPC, and V belts, but it also has the oil fill built in to the IP Gear cover? I pretty sure it's a 6.9 but after learning about the Oil fill differnecs I'm not so sure

 

[dyoung14]

My 87 has the bullet type GPs, solid state GPC, and V belts, but it also has the oil fill built in to the IP Gear cover? I pretty sure it's a 6.9 but after learning about the Oil fill differnecs I'm not so sure

in 87 6.9 had lots of 7.3 parts on and in them thats why the look the same, just look at the head bolts that will tell you all

 

[david85]

I know the 6.9 has 12 point bolt heads on the head bolts. Does the 7.3L have 6 point?

 

[F350farmboy]

Th3 7.3 also has 12 pt bolts heads.....at least the '90 motor I tore apart did.

 

[icanfixall]

The block numbers will tell the truth. The 7.3 started with number 500,079 and went to 1,116,330. Then the turbo 7.3 blocks started at 1,116,331 and up. Any lower numbers than 500,079 are going to be 6.9 motors. Any non turbo mor can be easily upgraded to turbo specs by adding turbo rods and pistons along with inconel exhaust valves. I have heard that some 6.9 motors have ben upgraded like this but have never seen one...

 

[sle2115]

My 87 has the bullet type GPs, solid state GPC, and V belts, but it also has the oil fill built in to the IP Gear cover? I pretty sure it's a 6.9 but after learning about the Oil fill differnecs I'm not so sure

Yep, they used the 7.3 style oil fill on the 87's as well. Mine is an 87 and IS a 6.9. Everything Mel listed for the 7.3 is on my 87 6.9.

Probably the easiest thing I found is:

Head Bolts - sure fire way
Fuel Filter - 7.3 used the filter head, center canister and bottom plate, with wiring going to the fuel filter head (6.9 has a spin on 1 piece filter and no wires going to the filter head).
Fuel Line sensor port - for lack of better terminology, the front cylinder fuel line has a port to time the engine

 

[sle2115]

in 87 6.9 had lots of 7.3 parts on and in them thats why the look the same, just look at the head bolts that will tell you all

Still had the firewall mounted water separator though, 7.3's had it all in the engine mounted fuel filter. I converted mine to the 7.3 system though, which was VERY easy, so that's not 100% either!

 

[Chevyboy_0]

I can't even find my water seperator...

 

[dyoung14]

someone put the 7.3 stlye water separater and fuel filter on my 6.9

 

[yARIC008]

The serpentine belts started in 1992.5. My 92 built in july 91 has v belts.

 

[hesutton]

I know the 6.9 has 12 point bolt heads on the head bolts. Does the 7.3L have 6 point?

All (6.9 and 7.3) have 12 point head bolt.

Did you get the turbo on yet Jason?

Heath