I did a Summit 5" exhaust with a 4" downpipe. It took a day to put in, alone at home. The down pipe wasn't hard at all. Would have been easier with someone holding it from the bottom. 99 7.3L, stick, crew, longbox, dually, btw. I put a tunner on it with no problems. Mileage was nearly the same, with more power. 17 mpg empty.
Watch always for oil leaks on the oil rails on both heads, and the back of the hpop. O rings go bad. Look for oil in your valley pan consistently, leaks look like rear main seals gone bad. Co-worker has a 500k 7.3L original motor, hpop replaced. He said to watch the oil dipstick to pan area too.
I think the tunner will change automatic transmission shift points, lower for better mpg. Burns up transmissions. The 6 speed is solid, and you should have no problems.
Man I must have done something wrong. My buddy and I did a whole turbo back exhaust on my 2002 F250 (same engine/cab) and it took about 3 hours including drinking beer and playing around. Truck wasnt super duper clean, had 250k miles on it. Yes we did the downpipe too, right off the turbo with the V Band clamp.
I figure someone here might know off hand, what'd they do at the 2003 to make it so much more powerful?
2003 MY was the release of the 6.0. More HP and TQ from the factory than the average 7.3 tuned up had. 7.3 tuning has come a long way since then!
94 MY was the release of the 7.3 DI HPOP. First use of name powerstroke (for the 7.3) Before 94 MY the 7.3 (and earlier 6.9) were IDI, mechanical injection pump
In reply to accordionfolder :
Intercooler for one thing. It was my impression that 94 still had some idi's and the powerstroke didn't come in till late 94 or 95. the new body style motors got the intercooler which was more powerful- perhaps even a different hpop? To me, the obs powerstrokes are a dog until you add a tune and then they are great trucks. I never lacked for power on mine, would have been nice to have the allison transmission that the later v10's got though.
As we were discussing the down pipe / firewall, some of us may have forgotten he had the newer cab! I was recollecting OBS hammer stories.
the 3" down pipe and 4" straight pipe is all the exhaust needed, unless beefing up hard parts and really throwing fuel at it. The 5" , on the kinda power your looking for is just louder, sounds hollow, and looks impressive for bragging' rights. YMMV.
In reply to grover :
The intercooler started on the '99, as you mentioned. The few '03 7.3s had the same power as earlier (maybe a few more, I know OBS better )
But the huge difference in power came Mid Year 03, when they slid a whole new engine in!!!
In reply to grover :
I'm not familiar with an Allison trans ever being used by ford light duty trucks. (Yes, a 350 is a light duty truck) The ford v10 uses the same trans bolt pattern as all the mod engines of the times.
The F450s and 550s used the same transmissions as the light duty 250 and 350, as far as I know as well. F650, is a whole 'nother animal. 
Maybe in the RV's, but I'm not sure about that either
In reply to 03Panther :
Oops, this was on a 7.3 specific website, I didn't realize they were just throwing in the 6.0 like that (I don't keep up well with MY changes). That makes a lot more sense. I think the 6 position tuner + downpipe + EGT setup is where I'll start (as recommended by many on here). Like I said, nothing is wrong with it, but this truck is heavy empty so I'd love a bit more poke. Funny though, with the cars I move around on it - it drives identically and gets identical gas milage empty or loaded. Fingers crossed with the tuner for a few more MPG too, 11MPG isn't the best.
03Panther said:
In reply to grover :
I'm not familiar with an Allison trans ever being used by ford light duty trucks. (Yes, a 350 is a light duty truck) The ford v10 uses the same trans bolt pattern as all the mod engines of the times.
The F450s and 550s used the same transmissions as the light duty 250 and 350, as far as I know as well. F650, is a whole 'nother animal.
Maybe in the RV's, but I'm not sure about that either
Most of the differences I've found in the F-550 (not that I'm looking super hard) seem to be in the rear axle+springs and maybe the brakes. The engine/trans and the rest seem to be exactly the same as any other 7.3 truck. One of my favorite differences though is the non-coded keys! No programming for the passive alarm system even though it's a 2000 ford truck.
In the OBS, frame was a LOT heavier ,and different width , and straight axle in front (2wd). I assume yours is straight axle?
In reply to accordionfolder :
I didn't see it mentioned yet but one very big gain without affect of reliability (per a customer source that worked at a diesel performance shop) is the intake manifold (or intake Y pipe/ plenum). Apparently the stock one favors airflow to one bank (I don't remember which). IIRC they had said if was a 20-30HP gain on a stock to mild build by switching to a design that evened out the airflow.
In reply to 03Panther :
Yep, it has the "mono-tube" front suspension or something like that - like a great big wagon axle, but still only 2wd. I would assume you are correct about the frame being much heavier as well to go along with it all.
In reply to asphalt_gundam :
Hmm, I didn't see that mentioned (or if they were I didn't understand) and that would be one of the easier things (I assume) to change out.
accordionfolder said:
I figure someone here might know off hand, what'd they do at the 2003 to make it so much more powerful?
In this aspect, it's far simpler than a gas engine. Diesels are strictly more air, more fuel. Old-school 12v cummins you could literally drive off the lot and use a flathead screwdriver and double the power and torque.
To an extent, you just add fuel which adds mass to the turbine gasses, which pushes more air in the intake. You obviously reach a point where EGTs become an issue or surge is imminent or it falls off the efficiency map... so you put on a bigger turbo and keep going.
Plenty of Cummins, Dmax, and Stroke diesels out there making well over 2000 lb-ft and 1300 hp, and they idle like a kitten and tow 12,000 lbs for a living.
accordionfolder said:
I figure someone here might know off hand, what'd they do at the 2003 to make it so much more powerful?
Pretty much covered it - different ECM, different tune, different turbo, different injectors, added intercooler, different low pressure fuel pump, different high pressure oil pump.
Also note that you are seeing manual trans programming, the so called 7.3 HO (never officially called that but the tune was different on the late manual trans trucks). The auto trans were tuned lighter.
Another thing of note is that the light duty (F250 & F350) are sometimes rated higher than their same year commercial equivalent, certainly to reduce warranty claims on the heavy loaded stuff and also for bragging rights. By 2003 the 7.3 was a dog compared to the Cummins and Duramax offerings.
In reply to 93gsxturbo :
Did no one notice that it compares mid year 94 (the release of the 7.3 DI) to mid year 03 (the release of the 6.0)
The only reason the different ECM, different tune, different turbo, different injectors, added intercooler, different low pressure fuel pump, different high pressure oil pump, made that difference (as per the chart) is because all that is different, due the completely different engine!
There were some minor differences from 94 1/2 to early 03, for reasons covered, but not 65HP and 100 lb. - ft. from the factory. That took the release on the mid year 03 6.0. Now aftermarket HP, 'nother story. But as asked? Ford changed to a different engine!
In reply to 03Panther :
That's 94 7.3 compared to 2003 7.3. The 6.0 also came out in 2003 but the power figures are 325hp vs the 275hp 7.3 with a manual of the same year.
Damnit you guys. I just ordered up a bunch of stuff to intercool my '97.
I wasn't even looking to mod this thing!
yupididit said:
In reply to 03Panther :
That's 94 7.3 compared to 2003 7.3. The 6.0 also came out in 2003 but the power figures are 325hp vs the 275hp 7.3 with a manual of the same year.
I stand corrected! Thanks. I've only owned (or worked on) OBS 7.3s. I know the 03 had both engines, and that a lot less 7.3s were made that year. But the MY 03, with no other qualifiers... had me fooled. I know the 99 intercooled boosted a bit, but even with MT, that 275 surprises me!
iansane said:
Damnit you guys. I just ordered up a bunch of stuff to intercool my '97.
I wasn't even looking to mod this thing!
Hahaha, I swore I wasn't either, but now I'm pretty sure if I add a bit more power I can re-gear the rearend a bit lower and do better than 2500rpm @65mph....
In reply to 03Panther :
Yeah, that power bump is pretty substantial! Though with the various tunes and fairly straightforward mods it looks like I can add a bit more power too...
accordionfolder said:
Hahaha, I swore I wasn't either, but now I'm pretty sure if I add a bit more power I can re-gear the rearend a bit lower and do better than 2500rpm @65mph....
For the mild 90's performance mods my 95 had, and the bone stock 96, 1900 RPM was the sweet spot! Now on the stock 96 X cab dually w original 215/85R16s on her, 1900, on the interstate with no load in the truck, she got 26 mpg! But 58 mph going down I75 in FL at 2am, is hard to stick too!!! Driving it like a normal person, 'bout 16. Quite pleased with that! Sold that for the FL50 before I ever did any mods,
mdshaw
HalfDork
9/30/21 6:48 p.m.
My '97 van/truck has no room for an intercooler so built my own water meth injection system. It injects 1gph at 5psi & adds 5 more gph at 20psi.
Since it's a '97 it's got forged rods & pistons.
Made a 3" intake & adapted the huge bucket size 6637 air filter. Installed 185/80 injectors, big hpop, new lpop, 4" down pipe & 4" exhaust. Since it's a van it has the bigger turbine wheel. Removed the mechanical fuel pump & added a Bosch with pre water separator & filter.
Jelli-Built made 8 custom tunes PHP Hydra) for it. The controller is in the top of the 4 port pillar gauge pod, along with egt, boost & trans temp.
On the Hot Street tune, stock Subaru STI's can't beat it from a stop or rolling. There is another tune -Race which I haven't used.
03Panther said:
As we were discussing the down pipe / firewall, some of us may have forgotten he had the newer cab! I was recollecting OBS hammer stories.
the 3" down pipe and 4" straight pipe is all the exhaust needed, unless beefing up hard parts and really throwing fuel at it. The 5" , on the kinda power your looking for is just louder, sounds hollow, and looks impressive for bragging' rights. YMMV.
According to Diamond Eye, the 4" is good to over 700 hp. When I did mine a couple of years ago, I could see no way how a 5" would clear the spare tire as the 4" was crowding it pretty tight.
