emccomas

OK, I have some basic questions about Rochester FI units, specifically about parts.

I am building (long term) a 63-65 style Rochester EFI system.

I want it to "look" as correct as is reasonable.

I have a plenum and lid.

I need a baseplate / manifold.

Other than part numbers / date codes, are all baseplates the same? In other words, will a 1957 baseplate fit a 1965 plenum and function properly "in this application".

Same question applies to fuel meter housings? I want to hang an empty housing on the side for appearance.

Will a 1957 or later fuel meter physcally attach to a 65 plenum and "look" reasonably correct.

You see where I am going here.

What parts can I use on a 65 plenum to make the system "look" more correct.

MikeM

Simple. Use all 7375(R) '63 or 7380, '64-'65 components.

The early manifold won't fit the later plenum.

jim lockwood

A sand cast fuel meter, like used exclusively in '57 and on a few '59 FI units would instantly look out of place to anyone familiar with FI. Any die cast fuel meter ('58 and forward (except for previously noted some '59 units)) will look "right".

Footprints of '62 and older FI units are all the same. Footprints of '63 - '65 FI units are the same. As Mike pointed out, they are not compatible between FI generations.

Grampy

Look correct to who? The unschooled won't be able to tell what you've done and the cognicenty will see all that is not original. The fuel meter case just bolts on so you could add it later when you find one. Most folks at car shows will just think it's cool.

63Corvette

Let me jump in here with a comment...
I think you are looking at a lot of frustration and expense for yourself if you attempt to try to make your pieces into a working FI unit. I recommend that you contact Jerry Bramlett or equal (Tom Parsons) and ask them for guidance and mentoring on this project. Even if someone GAVE you the missing parts for FREE, there is little that you can do to make them into a functioning FI unit without EXPERT Rochester FI guidance. Sorry, but that's just the way it is.

emccomas

I am NOT building a Rochester FI system.

I am building an Electronic Fuel Injection system using some Rochester FI parts.

The only parts absolutely necessary for this EFI conversion is a plenum, a lid, and a baseplate. I have the plenum and lid. I need a 63-65 baseplate.

Everything else from a Rochester FI system is "nice to have", like an empty fuel meter housing, assorted lines, etc.

Obviously, I will also need a throttle body, electronic injectors, fuel rails, etc. as well as a upgraded gas tank.

My goal is to make it look as original as possible, but use EFI to provide the fuel.

emccomas

Thanks Jim.

So I clearly need a 63-65 baseplate, but I may be able to use a fuel meter housing, etc from a 58-65, except for some 59 units.

I will not worry about an FI distributor or correct air cleaner.

jim lockwood

You got it, Ed.

Here's an idea you didn't request: Install Rochester FI fuel spider, nozzle blocks, and (empty) nozzles (available as reproductions). Then connect one central EFI nozzle out of sight up under the plenum to drive fuel thru the spider and "nozzles".

Such a setup, if it would work, would be a lot more convincing than the appearance of EFI nozzles out in plain sight.

Just a thought.... and worth every penny you paid for it.

Jim

emccomas

Interesting idea Jim, but would this not change the EFI from sequential fuel injection to constant flow?

I am certainly NOT an expert of fuel injection systems, but it also seems like using a single sequential nozzle would only supply fuel once for every 8 cylinders.

I definitely need to learn more about fuel injection systems in general.

jim lockwood

I'd say it would be approximately constant flow because the one central nozzle would still need to be pulse width modulated to vary the fuel flow in proportion to engine needs. So in the most literal sense, it wouldn't be "on" all the time but it would be constantly cycling on/off.

The nozzle doesn't know if it's a sequential nozzle or a batch nozzle. That is determined by how it's used which would be a function of the code running in the controller driving it.

My hunch is that the typical nozzle used in sequential EFI might not flow sufficiently to provide for all 8 cylinders. However, a nozzle intended for used in a throttle-body injection system would and it's that kind of nozzle I'd be considering.

The show stopper in my goofy idea might be how you would plumb an EFI nozzle into the Rochester FI spider system. The nozzle is designed to spray into an air stream, not to connect to downstream plumbing. I've never looked at solving this problem. It might be trivial or it might be daunting. I just don't know.

Jim

emccomas

It IS an intriguing idea.

MikeM

Seems like you might be creating something that will give you some of the same hot restart and hot driveability problems some have with the mechanical system by not having (high) pressure all the way to the injection point?

jim lockwood

Um, maybe, but I don't think so.

Upstream of the EFI nozzle fuel pressure will be high enough to preclude perc problems.

Downstream (in the Rochester spider and empty nozzles) do you really care? And what if the fuel does perc... wouldn't that actually be a Real Good Thing because you want fuel vapor to be drawn into the cylinders for easy combustability.

The problem with Rochester FI perc is that once it starts, the mass of fuel being pumped to the nozzles goes waaaay down causing a lean condition. With the upstream high pressure nozzle moving the fuel, liquid or vapor, the mass of fuel being pumped remains the same.

So, after 32.1 seconds thinking about it, no I don't think there would be a perc problem.

Grampy

A single injector would take a lot of work. With one point of injection you would run in batch fire (1 pulse) mode. For comparison, throttle body kits use 4 injector in the 4 barrel units. For a single injector you would need something like a 245 #/hr injector (which are available) but I'm not sure the typical ECU drivers would handle that load. The spider would have to be extensively modified to accept the injector and packaging the assembly would likely be a challenge. I also question if the ID of the small spider lines would flow enough at only 4 bar with a batch fire timed pulse at max power. The original system flows continuously (more time) at variable pressures and would run up to about 16 bar (higher pressure) at high RPMs but EFI uses regulated constant pressure. The injector flow rate is measured discharging into atmospheric std temp and pressure but the small spider line would probably have considerable backpressure and so reduce the injectors flow rate. If the engine runs lean under load bad things can happen.

Grampy

emccomas

Yes, this would be a challenge, but I am well known at work for thinking outside the box.

Remember the goal is the for system to "look" original. There is nothing that says it has to perform the same function as it originally did.

OK, think about something like this.

The copper lines of the spider don't actually carry fuel. What they do is hide the wire(s) for the electronic fuel injectors.

And no, I don't have any idea how to make that happen, but let's say for the sake of argument that I can locate some injectors that would allow something like this.

Or perhaps the real injectors are hidden inside / underneath the plenum, and the fake injectors with blocks and the spider are in their normal position.

Again, just thinking outside the box.

Remember, I can modify the inside of the plenum and baseplate any way I need to.

Not saying that IS the plan, but maybe it is an option.

Now that I am thinking about it, what about something like this..

Each electronic injector is hung on a bracket that attaches inside the plenum. Each injector is pointed directly into the port that it provides fuel for.

The wiring and fuel supply for the injectors comes into the plenum through the fuel meter housing, which is essentially empty.

The air meter side is, of course, replaced with a throttle body like we would normally expect.

But what if we custom make a throttle body that looks externally like an air meter setup.

Just thinking out loud....

Grampy

Well......There is plenty of room in the doghouse plenum to mount an injector in each port. You could hide a Cannon plug to wire them and use one of the existing pipe thread ports with a custom fitting to bring in the fuel. However, I'm pretty sure that having uncertified electrical devices in an explosive atmosphere environment is not a good plan.

It is possible to use an original air meter if you want. The air meter will need to be modified to drive a throttle postion sensor and you need to make provisions for an idle air controller which takes it's air from above the throttle plate.

emccomas

As you have pointed out, there are plenty of technical challenges to be solved.

I look on each of them as just another opportunity to excel.

Remember, we can do ANYTHING we want to the inside of the plenum. There are plenty of ways to isolate electrical devices (the electronic fuel injectors) from the "explosive atmosphere".

So, lets just assume that externally we have what looks like a 63-65 constant flow fuel injection setup.

However, no fuel is coming through the "injectors" that are attached to the copper spider lines. And the injectors themselves are probably just plugs the seal the hole.

Inside the plenum, each runner is extended with tubing so that each cylinder is effectively isolated from the others.

The air meter is a common point that connects to all of the runners inside the plenum.

Each runner has a place to mount the electronic fuel injector.

The runners either come together inside the plenum, or are each individually capped off.

Essentially, you have a electronic sequential fuel injection system hidden inside the plenum, and under the lid, of the Rochester FI system.

Then it is just a matter of getting the fuel, air, and electrical signals into the plenum, and that part should be easy.

The air meter (with a throttle position sensor attached) provides the air. We can disguise the throttle position sensor to look like something else.

The empty fuel meter housing provides the fuel. This is one area where we have to penetrate the plenum with a fuel line. Perhaps on the bottom of the plenum.

The wiring for the electronic injectors could come in a number of ways. One thought is to run the wires through the spider and fake injector nozzles.

This whole idea will need some more thought, and obviously some engineering effort. I also anticipate some aerospace type machine work as well.

Both the engineering and the machine work capabilities are more then plentiful in the Huntsville, AL area.

MikeM

Part of the reason the Rochester design ran so well and had good throttle response was because of air flow and the injector being just above the intake port in the head.

If you get the plenum plugged up with injectors, wiring, fuel rails, brackets and other things, your results might be less than desired.

Take a look at Wm62's (Bill Fleckenstein) home brew he made up. Looks good to me.

emccomas

Yep, understood.

But there are lots of options, and I am not taking ANY options off of the table.

Another consideration is a GM style throttle body injection system inside the plenum.

Plenty of ways to skin this cat.

And I really do like what wmf62 has done with his setup.

jim lockwood

You may have missed the part where I suggested using empty nozzles for this proposed arrangement.

The high pressure typical in real Rochester FI units is needed because each nozzle has a metering orifice which can be as small as .011". My recommendation is to remove the metering orifices and filter screens so the nozzles no longer present a flow restriction. The ID of a nozzle line is significantly larger than the hole in the metering orifice; I can't imagine it being a restriction to fuel flow.