Turning Up a N/A 7.3
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Junior User
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Turning Up a N/A 7.3
I have a 1989 International S-1600 with a N/A 7.3. It will run about 71 mph ( RPM limited ) or so at 20K gross which isn't bad, but I want a little more for passing, skirt checks, etc. It doesn't black smoke at all, even on hills, so I think one flat on the fuel screw might safely help a little on the power, but not the RPM. I think another 200 RPM would be plenty for an occasional burst without hurting it, this should allow me to run around 78 mph when needed. Is the pump going to have to come off and go to a pump shop, or can I "SAFELY" do this without pulling the pump. I really don't want to spend 2K on a turbo setup right now, but if the right deal came along who knows. I also thought about an occasional little burst of Propane which might be the most cost effective answer. Any help will be appreciated.
Posting Guru
Joined: Aug 2006
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From: Kent WA
FWIW, it is an easy enough process that, if it were me (or rather when the time comes for me to do this) I would (will) do it 1/2 flat to start with and see how it goes. If that isn't enough, you can easily do another 1/2 flat again.
Here's a good article explaining how to do it, step-by-step, with pictures even.....
http://www.members.shaw.ca/k2pilot/I...%20article.htm
Here's a good article explaining how to do it, step-by-step, with pictures even.....
http://www.members.shaw.ca/k2pilot/I...%20article.htm
Posting Guru
Joined: Oct 2003
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From: Monroe, WA
You can go 1 flat on a N/A engine, but they do tend to put out some black smoke until you get the Rs up. I'm not sure how to "backyard" set the governor, so that would have to go to the pumpshop. 
Without extra balancing I wouldn't try it.
Without extra balancing I wouldn't try it.
Post Fiend
Joined: Nov 2003
Posts: 21,285
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From: Nutter Fort, WV
It may take more than 1 flat, International was very conservitive with the fuel and timing on their engines compared to Ford.
Do you know how many RPM's you are turning?
What is your tire size and gear ratio?
Is your transmission a direct drive or overdrive in high gear?
I can figure the RPM from that if I know the tire height from the ground to the top.
Do you know how many RPM's you are turning?
What is your tire size and gear ratio?
Is your transmission a direct drive or overdrive in high gear?
I can figure the RPM from that if I know the tire height from the ground to the top.
Last edited by Dave Sponaugle; Nov 15, 2006 at 05:59 PM.
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It turns around 3200 or so topped out in high gear ( 1 to 1, no OD ) I dont remember the tire height off hand 245-75-19.5, but I figured it once at somewhere around a 4.88 gear. I don't want to get crazy with it and burn it up, so I figured 1 flat at a time until I at least see a little smoke at the hit.
Post Fiend
Joined: Nov 2003
Posts: 21,285
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From: Nutter Fort, WV
I forgot to welcome you to the site and the forum.
Locomotivebreath,
Welcome to FTE and the IDI diesel forum.
245/75-19.5 should be about 33" tall.
A 4.88 gear with direct drive would give you 3600 RPM at 72 MPH.
A 4.56 gear would give you 71 MPH at 3300 RPM.
Ford has the redline at 3600 RPM yellow is at 3300 RPM. I know mine will turn 3600+.
I would adjust it till you get a very light black out the exhaust, heavy black = dollars out the tail pipe.
Even at a light black, turning 3000+ RPM it will like fuel a lot.
Do you have any idea where International has the injection timing set at?
I am running 9* BTDC using the pulse method. Helps with pulling power a good bit.
Locomotivebreath,
Welcome to FTE and the IDI diesel forum.
245/75-19.5 should be about 33" tall.
A 4.88 gear with direct drive would give you 3600 RPM at 72 MPH.
A 4.56 gear would give you 71 MPH at 3300 RPM.
Ford has the redline at 3600 RPM yellow is at 3300 RPM. I know mine will turn 3600+.
I would adjust it till you get a very light black out the exhaust, heavy black = dollars out the tail pipe.
Even at a light black, turning 3000+ RPM it will like fuel a lot.
Do you have any idea where International has the injection timing set at?
I am running 9* BTDC using the pulse method. Helps with pulling power a good bit.
Last edited by Dave Sponaugle; Nov 15, 2006 at 09:04 PM.
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It is probably the 4.56's. The truck gets about 9 mpg loaded right now, and about 10 mpg empty. I tend to push it a little harder when it's empty. I don't know what IH calls for on the timing, but I think they rate them 5 to 10 HP less than the Ford pickup versions. Is that 3600 with the 6.9 or 7.3? I would think the 6.9 would safely twist a little better than the 7.3, but I wouln't be afraid of short bursts to 3500.
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Post Fiend
Joined: Nov 2003
Posts: 21,285
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From: Nutter Fort, WV
I have a 6.9.
The internals are the same for both engines, the only difference is the bore, heads, pistons and head bolts. The larger size headbolts is the reason the heads are different.
I am running 7.3 rockers and valve springs on my 6.9, direct bolt on replacement.
Cam, crank, connecting rods, oil pump, lifters, bearings, valves and gaskets are all the same.
Some 7.3 turbo motors did have larger wrist pins is the only other exception.
NA 6.9 and 7.3 had 1" wrist pins.
Some 7.3 turbo motors had 1 and 5/16" wrist pins.
6.9 - 7/16" head bolts
7.3 - 1/2" head bolts
6.9 compression ratio is 22.5 to 1
7.3 compression ratio is 21.5 to 1
I have seen several dyno sheets that had 7.3 turbo max no load RPM at 3550.
The internals are the same for both engines, the only difference is the bore, heads, pistons and head bolts. The larger size headbolts is the reason the heads are different.
I am running 7.3 rockers and valve springs on my 6.9, direct bolt on replacement.
Cam, crank, connecting rods, oil pump, lifters, bearings, valves and gaskets are all the same.
Some 7.3 turbo motors did have larger wrist pins is the only other exception.
NA 6.9 and 7.3 had 1" wrist pins.
Some 7.3 turbo motors had 1 and 5/16" wrist pins.
6.9 - 7/16" head bolts
7.3 - 1/2" head bolts
6.9 compression ratio is 22.5 to 1
7.3 compression ratio is 21.5 to 1
I have seen several dyno sheets that had 7.3 turbo max no load RPM at 3550.
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Posting Guru
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From: Kent WA
Originally Posted by locomotivebreath
Thanks fellas. What about the propane, anyone tried it?
I've got 95% of the details worked out for a 3-stage system that will meter the propane according to RPM & throttle position.
Gotta' get my exhaust & intake mods done first. I'm thinking I should have my propane system installed and tuned by around Christmas or New Years.....
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Junior User
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Im thinking about using a spray bar off of an old nitrous plate as well as the nitrous solenoid for the system. This would allow easy pill changes for tuning. I was also thinking about a progressive nitrous controller to ramp up the propane flow smoothly.
More Turbo
Joined: Nov 2004
Posts: 577
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From: Cumming, Iowa
Loco, Be cautious about high rpm's with the 6.9 My first straight truck was the same one istalled a Hypermax turbo kit made a world of difference. Had to pull a head about a year later(broken g/p tip pulled the valves from the head on that cylinder the tip came from to look for damage, the seat of the valves had another ridge or minor grove beat into it. mech said it was from constant high rpm's. and i knew he was correct I drove the truck 10+ hrs a day always matted to the floor. 2400-2500rpm all day long no problem but after what i saw back then 15 yrs ago i would stay away from 3000+ all day long. sold the truck it's set up as a spray rig now applying herbicide and still running most likley never gets to 2000 rpm's in the field.....