What's new
By:
Filters

F800 12 Valve Specs and tuning

DRTDEVL

DRTDEVL

Mothfukle
Joined
May 19, 2020
Member Number
78
Messages
768
Loc
Austin... TX? Nope. Minnesota!
I'm keeping the F800 instead of flipping it... its just too nice of a tow rig to lose for a couple years. The end goal is a large slide-in camper on the front part of the flatbed, then extend the bed 5' for a long beaver (the axle is pretty far back anyway). The engine is a 12V 5.9 ISB @ 210 hp. Not sure on the torque output, but it seems the MDT applications got higher torque output than the Dodges, I think its around 400 or so.

Right now, the plan is to install a pyrometer, slide the fuel plate forward, set the pump to 16* or so, and put in a 3k GSK while leaving the turbo and injectors stock. Upgrading tires/wheels to 11R22.5 on aluminum as opposed to the 10R22.5 steel. Adding the KDP tab. Hopefully I can get an exhaust brake on it, too. The Eaton 6-speed and clutch is good for 550 or so of torque input, so I don't want to get past that mark by too much, I just want to wake the thing up. Right now it has a 2500 GSK, and holds 68 on the flat. 66 when towing an empty car trailer. 64 with a vehicle on the trailer.

I believe the truck is around 13k empty with the big flatbed on it, and will rise once mods are complete to about 17k. Add another 7k for the Land Cruiser on the tail, and it will roll down the road at 24k. Add my buddy's Cruiser on the trailer, and that's another 9k out back for a combined 33k (GVWR is 26K, tow rating is another 20k, for GCWR of up to 46k).

1st question: Will sliding the fuel plate and adjusting the AFM wheel meet my power goal of around 325/550?

2nd: Will 325/550 be too much for the baby Cummins to handle long-term, provided its only driven by a semi-responsible adult (me)?

3rd: With said mods and rolling at up to 33k GCW, how likely is it that the truck will last a few years?

Any other cheap upgrades to consider while working on it? This is a total budget weekend getaway crawler hauler and potential bug-out vehicle.

Fun note: When searching for "1998 F800 specs" on the goog machine, I found my truck listed for sale at a dealership in CA. Obviously its no longer in stock, as I probably bought it from the guy who bought it from them. It has since been cleaned up nicely with a lot of work put into it before I got it. My F800 in a past life
 
Model Year​
Horsepower​
Torque​
1989 - 1993​
160 hp @ 2,500 rpm​
400 lb-ft @ 1,600 rpm​
1994 - 1995​
• 160 hp @ 2,500 rpm (auto trans)
• 175 hp @ 2,600 rpm (manual trans)​
• 400 lb-ft @ 1,500 rpm (auto trans)
• 420 lb-ft @ 1,500 rpm (manual trans)​
1996 - 1998​
• 180 hp @ 2,500 rpm (auto trans)
• 215 hp @ 2,600 rpm (manual trans)​
• 420 lb-ft @ 1,500 rpm (auto trans)
• 440 lb-ft @ 1,500 rpm (manual trans)​
 
Long term reliability should be fine as long as you don't drive like an idiot, make sure to keep an eye on the pyro. I've personally seen these engines with 250k+ open that still have factory cross hatching.

Can you get a bigger clutch? You may be okay power wise if you dont do mountains but don't expect to be doing 75 up a steep grade. Only thing I would look at would possibly be a smaller set of twins if it doesn't have the power you are looking for.
 
Pocahontas said:
Long term reliability should be fine as long as you don't drive like an idiot, make sure to keep an eye on the pyro. I've personally seen these engines with 250k+ open that still have factory cross hatching.

Can you get a bigger clutch? You may be okay power wise if you dont do mountains but don't expect to be doing 75 up a steep grade. Only thing I would look at would possibly be a smaller set of twins if it doesn't have the power you are looking for.
Click to expand...
Definitely not looking to dump fuel in the engine in an attempt to pull a grade at 75... the poor thing would melt down trying that!:nuke: The biggest possible future with me might find the Black Hills, but those roads are all lower speed limit during August anyway. I am on the MN/IA line... I could watch my dog run away for 3 days here!

Not sure about a bigger clutch, either, being a MDT and all. I'd really have to get someone in the know to dig through catalogs to find out what would fit that is stronger.
 
Do your plan and go from there, might be a bit sluggish, might be fine. You can always turn it up more but lots of service/ fleet trucks running around with 6bts so I wouldn't be worried about melting it down as long as you don't hold it to the floor going up mountains.

I have a 4bt step van that grosses around 16k regularly it definitely isn't fast but it will go 65 all day long. It is similar to your setup but with a small set of twins hx30/35.
 
DRTDEVL said:
The HX35 can support between 300 and 400 hp, that's why. Its currently only at 210.
Click to expand...

Well sure, but it's not that good at it. Just because someone can put down dyno numbers with one doesn't mean it's good useful heavy towing power. I didn't even consider running mine in my swap because there are better options for cheap. Look at an he351cw or a S300 type turbo.
 
YotaAtieToo said:
Well sure, but it's not that good at it. Just because someone can put down dyno numbers with one doesn't mean it's good useful heavy towing power. I didn't even consider running mine in my swap because there are better options for cheap. Look at an he351cw or a S300 type turbo.
Click to expand...
How does the HE351CW work without an electrical input signal?
 
What year F800? I have a 91 and it has I think a 6.6 Ford diesel.
Bought at Ritchie Bros for $2k unseen, driove it 5 miles and that's the last I looked at it.
 
My K30 has a MD 12 valve with a 180 p pump. I added a Super HX40 wheel and housing to the HX35 and ran it for several years and 50k miles after a fresh build and machine work. It has 5x12 injectors, 100 plate, 15.5 timing, AFC mods, 3k GSK. I was normally at 24k total weight and drove it by the pyro readings until it popped a head gasket towing up a big hill. I then went with a 62/65/12 DPS turbo and o ringed the head.

The Super 40 upgrade to your HX35 might be a good option for you with the mods that you listed.
 
AKnate said:
What year F800? I have a 91 and it has I think a 6.6 Ford diesel.
Bought at Ritchie Bros for $2k unseen, driove it 5 miles and that's the last I looked at it.
Click to expand...
1998, bought in CA when it could no longer be registered. 12 valve 5.9, Eaton 6-speed, 4.10:1 rear end, dual 50 gallon tanks. Had rebuilt injection pump, alternator, fresh hydroboost system, fresh cooling system. I rebuilt the AC and changed to LED headlights and drove it to Minnesota over the course of 3 days. I have new open-shoulder-lug drives in 11R22.5 flavor to toss on it, now looking for the right deal on aluminum outer wheels and a pair of inner steel wheels for them. Already put cheapo chrome lug covers on.

Pic in SLC on the way home:
Coming Home.jpg

pvkj454 said:
My K30 has a MD 12 valve with a 180 p pump. I added a Super HX40 wheel and housing to the HX35 and ran it for several years and 50k miles after a fresh build and machine work. It has 5x12 injectors, 100 plate, 15.5 timing, AFC mods, 3k GSK. I was normally at 24k total weight and drove it by the pyro readings until it popped a head gasket towing up a big hill. I then went with a 62/65/12 DPS turbo and o ringed the head.

The Super 40 upgrade to your HX35 might be a good option for you with the mods that you listed.
Click to expand...
This is the tech I am looking for...:beer:
 
YotaAtieToo said:
$25 aluminum plug and it works like any other turbo. You can then add a "boost elbow" or whatever.
Click to expand...
I like the spring controller better than the plug
YotaAtieToo said:
$25 aluminum plug and it works like any other turbo. You can then add a "boost elbow" or whatever.
Click to expand...
I have one of those plugs on my desk, if you want it DRTDEVL - I don't like them, so went with the spring controller.
 
What’s your rpm at 68 mph? 2,500?


Delete the fuel plate.

Power Driven Diesel’s (PDD) AFC LIVE & it’s AFC max travel & spring mod. It enable you to tune it from in the cab, and can control max fueling/power instead of a fuel plate. Tune on the fly, basically. Works great for me. :smokin:
powerdrivendiesel.com

AFC Live In-Cab Diesel Fuel Tuner | Power Driven Diesel

Add in-cab fueling control to your diesel engine with infinite adjustability with AFC LIVE In-Cab Fuel Tuner. Shop now and save on the best p-pump tuner.
powerdrivendiesel.com powerdrivendiesel.com

Upgrade to PDD’s 4,000 rpm governor spring kit. Your 2,500 rpm gsk gradually start to cut back on your fueling well before 2,500rpm mark, so you’re not getting the most of it despite if you’re still under 2,500 rpm.
powerdrivendiesel.com

PDD 3K/4K GOVERNOR SPRINGS

The PDD 3K/4K Governor Springs for Dodge Ram Cummins allow higher rpm and more power in your diesel. Shop now for your 1994 - 1998 2nd Gen Dodge.
powerdrivendiesel.com powerdrivendiesel.com

Advance injection pump timing to about 16*-17*. Maybe even 18*, if your cruising rpm is about 2,500 rpm. More timing, move power into higher rpm range & better on mpg.

Don’t assume you don’t have boost leaks. Pressurize & check for leaks.

Make sure your wastegate is functional, as I’d imagine your engine will run at cooler egt and overall happier if it’s cruising rpm is ~2,500 rpm, to not ‘choke’ it out.

5x12 injectors still will be an excellent upgrade, don’t be afraid to upgrade even with the stock turbo.
 
DRTDEVL said:
My K30 has a MD 12 valve with a 180 p pump. I added a Super HX40 wheel and housing to the HX35 and ran it for several years and 50k miles after a fresh build and machine work. It has 5x12 injectors, 100 plate, 15.5 timing, AFC mods, 3k GSK. I was normally at 24k total weight and drove it by the pyro readings until it popped a head gasket towing up a big hill. I then went with a 62/65/12 DPS turbo and o ringed the head.
pvkj454 said:
The Super 40 upgrade to your HX35 might be a good option for you with the mods that you listed.
Click to expand...

This is the tech I am looking for...:beer:
Click to expand...
What caused it to pop a head gasket? Excessive EGTs? We’re there signs? Or it just happened?
 
06h3 said:
What caused it to pop a head gasket? Excessive EGTs? We’re there signs? Or it just happened?
Click to expand...
A diesel mechanic that knows much more than me said that my drive pressure was probably too high. The small exhaust housing and 3" outlet of the HX35 were too small for my setup. 5x12 injectors and a 100 plate will put out a lot more fuel that the stock ones.
 
Last edited:
All the free AFC mods, delete fuel plate and slide the AFC housing all the way forward, 5x14's, 4Kgsk (set loose, so governed rpm is ~3500), 62/65/12 turbo.

Drive smart with an eye on the gauges.

Timing at 18* is a good balance between low end torque, high end HP, and noise.

This setup did 475hp/1103tq for me, with many trips in the 25k+ range (in an F250)

Your trans will take it, and maybe the clutch too.
 
You must log in or register to reply here.
Top Back Refresh