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Discussion Starter #1 (Edited)
The following was supplied by Pastor Bob(RIP)


GOVERNED SPEED/DEFUELING FUNCTION.


I don't mean to go on and on here but maybe this will help to understand it a bit better.

Ok....
Normally our pumps have a physical governed limit of roughly 2500-2550 RPM. That is the max upper limit that the engine will turn over under wide open throttle. This means that in "N" or "P" that with the throttle pedal on the floor, the engine will rev to 2500 or so and that's it, no matter how long you hold the pedal down, it won't climb any higher.

This limit is set using the "high idle" screw or governor screw. Under normal conditions the governed speed is preceeded by the defueling stage. By that I mean that around 2350-2400 RPM the injection pump starts to cut back the fuel volume or begins "defueling" as it's called.

This defueling happens due to one of two reason, or both reasons:They are > the engine RPM reaches a point were the governor conterweights open up and force the pump to start decreasing fuel amount.. and/or....The amount of Load on the engine decreases enough that the pump doesn't use/need as much throttle pedal to maintain speed.

One or both can kick in and cause the pump to defuel. Either way, the max speed is still set by the physical "high idle" screw setting, but the defuel point varies depending on the above factors. The high idle screw can be backed out to allow for a max RPM of as much as 3300-3500 RPM. Obviously that's a bit too high but it makes a point here....If you set your high idle or governed speed to, say....3000 RPM, the two defuel factors still exist. If the RPM climbs too high OR the load decreases OR both, the pump begins to defuel. In very general terms the defuel point usually starts roughly 200-300 RPM before max governed speed/RPM.

Now, the governor spring really does a couple of things, but primarily it does the following....

Lets use the 3000 RPM limit or governed speed again, as an example.

Under normal conditions you would start to see defueling at about 2700 RPM lets say.....With the governor spring in place that onset of defuel does not happen like normal. It holds the same amount of fueling you are demanding right up to the governed speed, then it finally looses the battle between the RPM and Load governor circuits and begins to defuel. With the governor spring in place and with that type of behaviour the pump can actually allow or permit an RPM "flare" above the 3000 RPM limit. This happens because instead of the fueling level starting to ease back prior to your governed limit (3000
RPM) the heavier fueling continues right up to or slightly beyond at physical governed limit of 3000 RPM. This can result in an RPM flare above 3000. I have seen a flare as high as 3700 RPM before the RPM/Load governor systems pull the fuel back drastically enough to stop the flare. It will finally settle back to the
3000 RPM level once this happens..... so.....In a nutshell you should do some RPM testing first. With the engine warmed up, and good oil pressure, slowly but firmly press the pedal to the floor. You would do this in Neutral or Park of course. This is the actual proper method of checking your governed speed as per the manual.

Make note of your top/max RPM. Ease out of it and let the idle come back down,... then repeat. You could have a consistent high idle of roughly 2500-2500 RPM. If that is the case the governor spring will allow heavy fueling (depending on the amount of gas pedal) right up to that RPM. If you back the governor scew out two to three turns and repeat you will see you governed speed (high idle) rise higher. Repeat until it's where you want it before installing the governor spring. I'd suggest 2900 RPM to start with and you can go from there depending on how the engine behaves after the install.

Hope this helps.
 

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Do you need to replace the spring to get more rpm or can some benefit be gained by turning out the screw some?
 

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Yes. Both is true. You can achieve higer rpm's by moving the screw back or replacing the spring.

In some cases if you want very high fuel rates then modification on the fuel linkages from the peddle to the injection pump is performed for increased throttle travel. This could be performed with or w/o a different gov spring.

Note that if you are to rermove the gov speed set screw from the pump, the injectionj pump throttle control lever will only move back far enough that removal of the set screw was a waste of time. To achieve further throttle travel the linkages on the truck will need modification.

be sure to perform a visual at the fuel supply line into the top of the pump. The late model engines have a fuel feed line that is known to "get into the way" of the injection pump throttle lever when seeking incresed rpm's.

60# valve springs are recommended for sustained high rpm's:hyper:
 

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Greenleaf said:
60# valve springs are recommended for sustained high rpm's:hyper:


Does the head need to be removed to change the valve springs? If not I'm still not sure I'd like to do it myself. I'd be afraid of dropping a valve into the combustion chamber. On a gasser I knew a trick which was nothing more than stuffing cotton cord into the cylinder through the spark plug hole then gently bring the piston to the top. make sure you still have cord hanging out the hole! :rof
 

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Yeah.........:lol3: I'd be the one setting in the folding chair next to the truck looking like :popcorn:

BTW it's all I do at the IN wrench day/cookout:thumbsup

Anyhow. No, the head don't come off. It's soooo simple you won't believe me;

You pull the valve covers, right?
Begin with the engine at TDC to fire #1
back off the valve adjusters
remove the rocker tower bolt
remove the head bolt
remove the rocker tower w/the rocker arms

(How will the valves go anywhere w/piston @ TDC? The piston to valve face clearance is like .064")

Use the valve spring compressor to compress said spring and remove the two keepers.
pull spring off valve stem
replace the stem seal if you wish
clean out the cyl head bolt hole very well.
insert new spring onto copressor and slid over the stem
install keepers and remoive the conpressor tool
hit end of valve stem w/a plastic mallet to seat the retainers.
install the tower w/ NO oil between it and the cyl head surface!
Insert lightly lubricated tower retainer bold loose like!
Lube the head bolt and torque to 120 Lbs/Ft torque
adjust the valve lash. .010 and .020 If I recall.:fist:

Rotate the engine to the NEXT cylinder to fire and stop at it's TDC compression stroke. You DO know the fire order, right:THREAT:

I have lots of trick and can supply you with some if need be.
 

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What's the firing order? I really really need to get a manual. That's really cool. the tollerance is so tight that the valve can't be lost if the piston is TDC. Cool! What's the best brand of spring in your oppinion?
 

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Uhhhhmmmm.......................... I'm 36. I ain't TOO OLD:THREAT: :butt:





:lol3:


I dun forgots to say that the small tower retaining bolt is torqued to 18 lbs ft AFTER the head bolt is tightened.

I purchased my springs from PDR in O'Canada. I don't know the "brand" of the spring.

-S
 

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Thanks for the firing order. Is there a mark on the harmonic ballancer to show you where TDC is? Can the engine be turned by hand? (I'm thiking not with the high compression ratios. I'd bet changing the springs at the same time you do injectors would make alot of difference. Otherwise I'm guessing bumping the starter is the way to get the piston lined up in the right place.
 

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I'm a little confused with the head bolt. I'm thiking of head bolts as the bolt that holds the head to the block. why would you even mess with that if all you are doing is reinstalling valve springs? Maybe it would make more sense if I pulled the valve cover and looked at it. As a general rule with head bolts I've always thought it's a good idea to replace them once they are loosened as they can lose the elasticity and are more prone to break. I'd think this would be more so with Diesels. I'm sure all I need is some clarification. Thanx for your help thus far. NORM
 

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Well now, see the second smilie proves my contention...that is, GL has more rings than a redwood.....older'N dirt and in on the design of said dirt...;)

pb....





Greenleaf said:
Uhhhhmmmm.......................... I'm 36. I ain't TOO OLD:THREAT: :butt:
:lol3:

-S
 

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Norm

Just ignore the previous post by PB. Someone should notify his aid he escaped from his room again.


:popcorn:




A head bolt holds the rocker tower to the top of the head. Just pull that thing and clean it and it's hole up really good like and coat the bolt threads and head with light coat of oil. Make sure no oil is between the bottom of the rocker tower and the head. Put the small rocker tower bolt in place but tighten only after the head bolt. Clean the small bolt in same manner.

Torque it.

BTW when you remove a head it's generally ok to reuse the bolts. The gasket kit will contain a gauge to measure the stretch.
 

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Greenleaf said:
Norm

Just ignore the previous post by PB. Someone should notify his aid he escaped from his room again.


:popcorn:




A head bolt holds the rocker tower to the top of the head. Just pull that thing and clean it and it's hole up really good like and coat the bolt threads and head with light coat of oil. Make sure no oil is between the bottom of the rocker tower and the head. Put the small rocker tower bolt in place but tighten only after the head bolt. Clean the small bolt in same manner.

Torque it.

BTW when you remove a head it's generally ok to reuse the bolts. The gasket kit will contain a gauge to measure the stretch.
I feel like I'm learning engines all over again. (I guess I am!) Thank you for all your help.
 

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Question about the location of the high idle screw?

Is this the same screw that I have seen called just the idle screw on several diagrams posted around here? Thank you for your help.
 

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Could someone please give me a quick description as to where this governor screw is located on the pump? Thank you.
 
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