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[cookingwithfat]

SO here is my latest exchange over at MO

OK, about vacuum.

Please work with me here as I am just learning all of this, but since the question of vacuum keeps coming up let me shed some light on what I have learned.

Vacuum is important because of the vacuum advance, which is tied directly to an increase in vacuum as RPMs increase. (If this is wrong, please explain why and ignore everything else I am about to write as it is directly tied to this concept.)

I have driven the truck in two situations where I have produced 4500 RPMs at 60 MPH. Both are the result of kicking the truck down, and in both cases the truck drops two gears not just one. So, I put my foot down on the gas and it drops a gear, then I push even harder and it drops another gear. I do not know if the pushing harder is actually helping to kick down further, as the pedal seems to be all the way down at this point, but it seems that it has an effect.

One on a flat stretch of highway which resulted in a smooth running rover that felt the way I think a well built British rust bucket should.

The second was on a very steep hill where in order for me to maintain speed I need to kick it down. It is in this situation where the truck very quickly heats up and goes into limp home mode.(Please know that prior to having to kick the truck down the temperature gauge indicates the truck is running perfectly.) Also, when it does go into limp home mode what I experience is a pronounced decrease in power with my foot to the floor. If I quickly remove my foot and then give it gas again I will get minor backfiring and bucking.

In both cases the speed and RPMs are the same. As it has been explained to me, and as I said above, vacuum is tied to RPMs and as such in these two examples the difference is load.

Will vacuum decrees under load?
Does the truck require more vacuum under heavy load, and if so, how is it produced if vacuum is tied to RPMs?

I have tried my experience in the name of science here folks. If there is something I have left out please ask.

To which I got the reply to switch out the injectors. Which I don't understand. I know I am not the most knowledgable on this subject, but if injectors are not causing a problem at 4500 RPMs at 60 MPH on highway then they are pushing the right amount of fuel. Steve points out that these are "orange" tops anf not "yellow" tops. I am confused by this though because the guy I ordered them from swore up and down they are the injector for the RRC and when they arived Steve said they were not right, so I called the guy back and he stood by his part, so I pulled the trigger and had them put in. Steve says tehy are under rated though, and I do wonder if I have the wrong Ford injector. But, if I do then they should not work ever, right?

Anyway, I replied to the post to swap injectors thus:

Kevin, I don't know that the injectors are a known problem. Let me put it this way. The truck when I purchased it had the same injectors in it as the new ones. Ford Motorsport Yellow tops. The truck as of right now runs perfectly with the exception of kicking down at 4500 RPMS at 60 MPH on a steep grade uphill. Now beyond the debate over whether the Ford injectors are a suitable replacement part how can swapping in old unknown injectors from a parts truck help me when I currently have brand new injectors in the engine? If my understanding of injectors is correct, they do one thing and one thing only: inject a specific amount of fuel each time they are told to do so. If these are the wrong injectors - or Ford injectors are an unacceptable alternative replacement part - would they not fail in other areas of performance, not just at 60 MPH @ 4500 RPMs?

To which steve replied

An injector that is rated for less flow will lean the engine- a lean engine goes damn hot under load. They are orange, not yellow BTW- according to Ford. They are rated lower flow than the original ones by 7lbs which is significant.

To which I put up two posts...

But as I posted above I have two ideal tests that result differently. Both produce high RPM situations, so if the injectors were at fault then I should have experienced over heating at 4500 RPMs at 60 MPH on the highway flat, just as I did at 4500 RPMs at 60 MPH on a steep incline. I know that I am new at this but logic dictates that going through the whole process of replacing the injectors again is not warranted at this point.

1. Injectors are tied to RPM - I did not know that before - and are constant, therefore the "wrong" injectors should produce faults when identical speed and RPM conditions are tested. This has not been the result of my testing.

2. Vacuum is tied to RPM as well - see statement 1.

Now, I went to bleed the cooling system again, just for good measure and noticed that one of the new wires was not actually connected to the distributor. Upon closer inspection I found another that very likely was detached as well. When I pushed them all into place I found two more that were particularly loose. This means at the very least the truck was running down one cylinder, and possibly as much as 4 cylinders were not working, or perhaps were working intermittently. So let me pose this question: could one cylinder not working cause over heating ONLY in situations where the truck is under heavy load while also pushing high RPMs? What about with two cylinders down? Three? Four?

I am searching for the answer but I am reluctant to return to the injector issue as I feel logic points away from that. No one has convinced me otherwise. While it would be nice to have genuine Land Rover injectors to simply say that I should revisit that issue because they are not genuine is not logical. If there is something about the way the truck is running that points to injectors then that I am interested in, but as you have described injectors - and from what I have read - I should experience the same problem in both of my test situations.

and then finaly...

Either things get sorted out soon or my honeymoon is off and my fiancee and I have to make alternate plans. (For those of you who are not aware, that is not an analogy. We really are planning on taking the rover on our honeymoon.) I am going to romp hard on the thing because if it can't make it up route 9 to Marlboro Vermont it certainly can not make it through the Rockies, and if it can't do that then it is a worthless piece of crap.

When I bought it worked. Ergo, the injectors are fine, the cam shaft is fine etc... and what I don't understand is the logic of this. I mean .. oh to hell with it, I have wasted enough of everyone's time. I'll either figure this thing out or off to the damn junk yard with the dumb piece of crap. Five months with no answers from anyone other than more fishing expeditions and a lack of money to do real work means this is a dead end. I'll keep tinkering with her until I break her, but I think we are all tired of this thread.

I just can't keep talking about injectors and cams when the truck worked when I bought it. I am trying to be scientific about this as it is the only way that I can address things since I have so little experience.