Low RPM governor speed

[Steven Donald]

Got a question. I've seen threads here talking about raising the governor RPM above the factory 3,600rpm and I am guessing most of that data is useful, but thought I would ask here for clarification.

My truck has been gone through by the PO, its a '91 7.3idi with the factory turbo system stolen from a '94. It starts immediately every time, idles great and has GOBS of power compared to my old N/A. turbo spools up to about 10psi at 2,000 rpm and tops at 15psi at 3,000 rpm and falls on it's face. It defuels starting at 3,000 and is done, wont go faster than 3,300rpm with zero load. This isn't a HUGE deal, but i feel like it's losing fuel right where it would be making peak HP and i just want to feel it! haha!

So my specific question. I've read that to change the governor RPM, you have to change the spring on the "torque screw" and that just adjusting that torque screw wont change the rpm, but how could mine be so close to correct and running awesome, but cut off too early? Any reasons anyone know of? If I took the top cover off, you think adjusting that nut to tighten (or loosen) the spring could get me just the extra 300 rpm I am looking for? Also, which way would it be? tighter spring = more RPM or is it looser spring = more RPM?

Thanks in advance for any reply, I appreciate your time!

 

[Thewespaul]

Very good chance that pump could be from a uhaul truck which had lower rpm governor settings than most trucks, but the 3300 is what should be the governed limit. You’re slinging a lot of iron at that speed, but you can raise the governed rpms by replacing your spring or by cutting 1.5 curls out of the stock spring and stretching it back to stock unloaded height.

 

[Steven Donald]

Awesome, so a "lighter" spring raises the governor then? I'm guessing you've done this job, eh?

 

[Thewespaul]

Haha maybe a time or two. My daily doesn’t have a governor so funny story, I was at the drag races one night with some friends racing a turbo mustang we had built. So decided my girlfriend (who couldn’t drive a stick) should take my truck for a pass. I gave her a lesson in the parking lot and then set her up on the starting line. Silly me forgot to tell her to shift at 3500... well she banged every gear once the indicator PASSED the redline... which happens to be 4500. That was almost 100k miles ago and still haven’t had an issue, but does make for a good story.

 

[Steven Donald]

Wow! How did you take the governor out? Just remove the spring? I'm just wondering, worst case scenario if I cut the spring too short, if that's the only issue I would have, or does that spring do something else also?

 

[Thewespaul]

Mine has a shortened 6.2 Detroit spring, so technically has a governor, but it’s about double stock and the engine would grenade before it reaches it.
If you have resignation on shortening the stock spring you can always just order a 6.2 governor spring. Without any modification it will set your governor around 4500.

 

[Steven Donald]

No reservation at all! I just want to make sure i am going the correct way with the spring! You can pull that bolt as spring with the IP still on the engine, correct? Obviously going to get diesel on stuff...

 

[Thewespaul]

That’s right. I’ve thought about doing a write up on the procedure but I don’t want to be responsible for when someone’s engine plays ping pong with itself... but here’s what you need to remove, make sure you take good pictures ahead of removal, you need everything to go back together the way it was.


Remove three bolts to pull the top cover

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This is what you will see, this is an early pump case so it doesn’t have the torque screw adjustment.

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Loosen this bolt and carefully slide the governor shaft out, remove and replace the governor spring and then reassemble

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[Steven Donald]

The governor spring is the largest of those two on the shaft, correct?

 

[Thewespaul]

Yessir that’s correct

 

[Thewespaul]

Brain fart. Short spring is what you can cut, don’t stretch it, stretch the longer spring out (or use a 6.2 spring in its place)

 

[Steven Donald]

Now I'm confused. Which one is the "short spring"?

So, I don't cut either spring, but I stretch out the "longer" one??? They look the same length to me? I'm lost...

 

[Thewespaul]

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Red is short and blue is long, sorry about that!

 

[Steven Donald]

So cut the short spring AND stretch out the longer one to make up for it?

 

[Thewespaul]

Other way around, cut long and stretch the short