Well, a new problem has reared its ugly head! It won't be a big issue until I get ready to install the engine into the truck, but..

It looks like the shop machined the fuel pump opening wrong. That, or I have the wrong pump (there is one that is pre 12/84 and post 12/84 for the 1985 4.9)
The block is a 1992, but had the spot for the mechanical pump; it just wasn't opened up. The opening is an oval, and I'm wondering if he had the gasket in the wrong direction when he marked it.

On this engine, with the pump I have, to get the actuator arm on the pump in correct alignment with the cam, the pump needs to be installed with the 'lines' on top. The machinist used the gasket as a guide, but put it so the pump is mounted with the lines down; upside down from my perspective; at least that is what it looks like.

Without the cam installed, the pump mounts fine but of course is in the wrong direction. Of course, it won't work because the cam won't actuate it and would actually cause damage if I tried to run it that way. So I either need a later version of the pump that might fit (??) or I need to block it off and install an electric pump.

Now the bigger problem is where to mount the electric pump should I need to go that route. I have dual tanks and no in-tank low pressure pumps, and I would like to just mount it under the hood. I know that these pumps push better than they pull, but with dual tanks that presents an issue.

If I mount it on the frame below the tanks, it would need to be forward of the selector valve and while it would be more of a 'push' for the front tank, it would still be a 'pull' for the rear tank. In effect, it would be not much different than mounting it under the hood.

I really wanted to avoid all that by machining for the mechanical pump but now it looks like I may have no choice.

Does anyone make a pump that is designed more to 'pull'? I'm thinking I'll have to also install a regulator so I can dial in the fuel pressure.

Is there something I'm missing with the mechanical pump issue?

What a pain...

 

I did a little more investigating and it looks like I can mount the pump and it will work, but where he machined the opening, since he put the gasket on wrong as a guide, the opening is too big. When the pump is mounted the correct way, there is about a 1/2" hole below the pump.

What I am wondering, is could I make a block off plate and machine it with the correct opening. That would block the extra space, but would position the pump away from the block a bit more (the thickness of the spacer).

That would change the way the cam drives the pump, but I'm not sure by how much and if it would make any difference, or at least enough difference to matter.

By moving the pump out by 1/8" or so, the cam would be hitting the actuator arm more towards the end and that would change the leverage a bit. I may just mount the pump using a washer or two under the pump and just see how much of a difference it seems to make.

I'm not sure how to test the operation though. As long as it won't harm the cam, I suppose I could just try it once I get the engine built and see if the pressure is ok.

Thoughts??

 

You won't get as much stroke so won't pump as much. But if it is adequate than it should work find. Worth a try.

 

My concern is that given the angle of the arm, by moving the pump out by 1/8", the cam lob will hit the arm at a higher point and drive the arm too far and bind.

I can test that by hand turning the crank though.

I think I'll have the machine shop make me up a plate to try it. They owe me at least that much..

As long as it doesn't damage anything, the worst case is I go with an electric pump. I really wanted to avoid that so we'll see..

 

Worth a try.

 

By spacing the pump out 1/8" you are applying the same stroke farther from the fulcrum.
The pump will see less, not more, action.

 

The stroke is based only on the lift of the cam lobe. As long as the arm is being 'touched' by the lobe throughout it's revolution, the stroke will be the same.

The possible problem as I see it is that since the arm is angled 'up', when the pump is moved out a little bit, the lobe contacts the arm a little sooner. It's possible that the arm may not be able to fully 'relax' and may also run out of travel before the cam rotates all the way around.

If the pump was able to move 'in', the lobe may not contact the arm at all in spots, in which case I would see a decrease in the stroke. In my case, I'm not worried about the total stroke, but rather the total travel available and if at the lowest point the pump is also at it's lowest point.

Confusing enough?

Maybe I'll try to sketch a picture and upload it.

 

No, the stroke is based by the 'lift' of the cam lobe x the distance from the fulcrum (of both sides)
The distance of the diaphragm arm is constant (as it is part of the pump)
If you shift he same travel farther away from the fulcrum on the actuator side, the diaphragm side is less.

It is a simple see-saw and the cam lobe rotates about its axis, so there is no angular component.

You don't need to try and school me in simple ratios or geometry.

 

I think we are getting physics and geometry mixed up. Or I am...

The arm will move only as much as the lobe of the cam will push it. The fulcrum point effectively changes as the pump moves further from the block.

The travel will be the same no matter where the lobe touches the arm, as long as it touches it through the entire rotation. The distance will be the same, but the force applied will be different since the point being 'pushed' moves further from the fulcrum.

To use the see-saw analogy...

Push the see-saw down 1 foot and the remote end goes up 1 foot. It doesn't matter where you push, as long as you measure 1 foot from where you initially contact the see saw, the remote end will go up 1 foot. If you push on the far end, it takes X amount of effort. If you move closer to the fulcrum point, it will take X+ effort, but as long as you still move it 1 foot, the remote end will go up 1 foot.

The distance traveled isn't affected, only the force applied (or the force needed to lift the remote end). The lift on the remote end will always be the same as the amount of downward movement on the near end, it's just the work that is affected. In other words, one end goes down X amount, the other end has to go up the same amount (see saw, equal and opposite reaction and such).

When the cam lobe is at it's lowest point, and still touching the arm, it will move the arm X amount as it rotates, determined by the cam profile. It doesn't matter where the cam touches the arm, it can only move it that same amount, provided the arm has enough travel and is in constant contact with the lobe. The lobe lift doesn't change, the work required does (that's the fulcrum effect)

Geometry determines the travel, which will always be the same as long as the cam lobe stays in contact. The travel is the lift of the cam lobe.
Physics determines the work, given a constant applied force (the cam rotation at a given speed). That's where the fulcrum point comes into play.

Moving the fulcrum away from the point of applied force (the cam contact point) will mean that the cam does less work to move the arm the same amount. There are two issues as I see it;

1. Will the arm stay in contact with the lobe when the pump is moved out, and, if so, does the arm still allow for the same amount of travel or will it always be somewhat compressed and then 'bottom out' at the point of highest contact. If it doesn't remain in contact, then of course the amount of travel will be less. The only reason it would run out of travel, I think, is if it starts out somewhat compressed. Since the arm is at an angle, as it moves away from the cam, it would have to compress just a bit.

2. Does the amount of 'force' at the remote end effect the operation of the pump or is it simply the travel? Since the fulcrum point moves away from the point force is applied, and that amount of force is constant (relative to rpm), does less 'effort' at the cam end affect how the pump works? The distance it moves will be the same but the effort required will be less. I assume that the pump effectiveness is a factor of arm travel and not force, but I could be wrong.

 

Force applied to the pump diaphragm arm is multiplied by the lever ratio.
If you move the force (or action) point of contact away from the fulcrum you multiply the reaction moment.

Inversely, the motion imparted on the 'reaction' side is decreased.

It is not any different than a high ratio valve rocker arm where the cam lobe (lift) is the same but the valve lift changes.
The loading on the pushrod and lifter increases in proportion to the ratio as well.

The resistance of the pump to the eccentric action is really miniscule.
I don't know the length of a 400's fuel pump arm.
The one on my 460 is perhaps 6", so 0.125" is not going to make much of a difference.
~2%??? 48/8 : 49/8

 

We are on the same page, just expressing it differently I think. The bottom line, as you said, is that the net effect of moving the pump out a little bit is negligible.

I spoke with my machinist and he admitted his mistake and gave me a refund. He is also making a special plate that will block the hole, with a new hole cut in it to allow for proper pump mounting.

I thought about using a thinner material and JB Welding it in place, but decided since 1/8" won't make a real difference, I'd go with the thicker material for stiffness.

So the current plan is:

Plate to Block with a thin layer of RTV between plate and block, then gasket then fuel pump. The plate should be stiff enough to seal with just the two fuel pump bolts. If not, I can always epoxy it to the block and make it a permanent modification.

Not the ideal solution, but if it works I can keep my mechanical pump and won't have to go through the hassle (and expense) of installing the electric one.

Everyone makes mistakes, it's how we deal with them that shows our character. That's what I tell everyone I arrest; it was nice to see my machinist step up and make it right.

That's why I'll continue to use him for projects and recommend him.

Like my Great Dane says - Drool Happens..

 

Well, we found a solution to the fuel pump issue.

There are 2 version of fuel pumps in 1985, pre and post 12/84. The primary difference is the orientation of the mounting flange.

As it turns out, my machinist cut the opening based on post 12/84. I had a pre 12/84 pump on hand and that is what I planned on using.

Once I found out what had been in the machinist's head, I bought a post 12/84 pump and guess what? Fit's like a glove...

Moving on..

The plan for this afternoon / evening is to install the pistons and perhaps the oil pump. That will just leave the oil pan and timing cover to complete the short block. That's the plan at least..

And yes, I still need to get some pictures posted..

 

very happy to read this.

if a machinist butchered my engine block incorrectly like that..... i would be irate!

actually, I would never let a machinist butcher my engine block, I would go for an external pump long before i would allow him to drill holes into the side of my engine block near my camshaft

 

I'm glad it is working out cleanly.

 

It's actually a pretty easy thing to open up the spot for the pump on the EFI block. He did a fantastic job, it was just a miss-communication regarding what pump. It looks great, just like a post 12/84 block.

Of course, it was done on the bare block and cleaned very well both before and after. The shop I used has done work for me before and has a very good reputation. It was just some confusion on both our parts. By the way, did I mention that he not only refunded his fee for the machine work, but also bought the new pump for me?

Happy Camper now..

For anyone else considering this modification - be sure to have the pump on hand first and make sure everyone is on the same page. The bolts that were already in place, that mounted the coil, are too short and if retaining the stock coil, you'll want to use studs to mount the pump, since the coil uses the same bolts / studs. My build is getting a DUI ignition so I just need slightly longer bolts.