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I have a Pantera project that I received in February this year.  It is a 1972 Pre L that is setup as a GTS and it came with a TWM 8 stack EFI that is driven by a Haltech ECU from the 1990's.  The car also came with nitrous and you can see the hard lines for it above.  I will be sidelining the nitrous and also want to replace the Haltech ECU with Holley Terminator X.  The Holley ECU needs a MAP sensor and from what I can tell the Haltech did not use one.  If this is correct then I need to create a small plenum for the MAP sensor that taps into each throttle body under the butterflies like the one below.

Since my nitrous hard lines are also below the butterflies, I am  thinking of repurposing half of the lines (either the NO2 lines or the fuel lines, and then plug the lines I don't use) to create the MAP sensor plenum that I likely need.  How does this sound to you?

Below is a photo of the bare throttle bodies sitting on the Hall manifold that was originally for Weber carbs.


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Last edited by stevebuchanan
Original Post

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In case you might be interested.

Holley Terminator X ECM: Mark Bailey still has a brand new (not used!) Holley Electronic
Control Module for sale. The new cost was over $1000; the current cost is (gulp) negotiable.
It turns out his setup required the MAX X instead of the plain old X.

Mark Bailey
(669) 333-2544

Steve, I had a customer with the same TWM FI hardware and ECU in a Pantera.

That Haltech ECU is only a 8 bit based microprocessor and peripherals ... barely able to support the engine especially at high RPM.

I replaced the ECU and added the plenum and MAP sensor the difference was a considerable improvement without changing injectors or any other engine components.


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Steve, I completely agree with your thought process. Lose the NOS and the Haltech ECU. The car will be much more drivable with the Holley ECU. Adding a MAP sensor is pretty easy. You need a MAP sensor plenum, MAP sensor, fittings and hoses. Rubber hoses are fine. IPSCO used to make a nice MAP sensor plenum. It’s one of those items that was never on their web site. The Holley ECU also needs both a Cam Sync and Crank signal, either from a dual sync distributor or a separate cam synchronizer and crank trigger (which would require distributorless ignition). The latter is better but more work and $. It may also require different TPS and CLT sensors. Maybe a different O2 sensor too. I assume the car gets vacuum for the brake booster from an electric vacuum pump.

Maybe Mark Bailey needed Drive-by-Wire!

Good luck !

Last edited by davidnunn

There has been significant development in aftermarket EFI kits since the "Blue Pantera" was built.

The Holley Terminator is Holley's solution. Edelbrock has one also called the FAST system.

I have the same eight stack system being talked about here and I am using the FAST. It is self learning. Plug and Play. It is about as simple and uncomplicated as these aftermarket systems are about ever to be.

You can easily go into the software charts and change the parameters but it isn't necessary. The software is already set to modify itself to achieve specific a/f points that have been dyno proven. You can change them if you want but so far from what I am seeing, it isn't necessary.

The set data is smarter then you are and the cpu is a lot faster at making the right changes then you can.

Also, FAST (Edelbrock) was wise enough to use very common (and inexpensive to replace) sensors in their system. That is a big plus for maintenance costs and longevity of availability of those components. There are no components shared with NASA, Ferrari, Porsche or Lamborghini. Just plain Jane GM production vehicles that will have service parts around for some time to come.

The FAST does use a MAP sensor to measure engine load. So it needs a common plenum chamber with all eight throttle throats plumbed to it, in a manner as if you were plumbing in a vacuum gauge.

Essentially that is what the MAP sensor is doing. Reading engine vacuum.

It should also be pointed out at this point, that the "vacuum gauge plumbing" does not need to be plumbed individually, each runner with a separate tube to the common vacuum box that you use. It works fine being plumbed in series, i.e., like Christmas Tree light wiring. Each line plugged into the other. That makes it much easier and cleaner to do on any car, particularly on a Pantera.

Theoretically, that Haltech is kind of obsolete now. It had to be programmed with a lap top for virtually everything.

It's main advantage at the time was thought to be that it fires the fuel injectors individually like an original equipment efi system does on a new vehicle.

For aftermarket uses, that is really not necessary and over complicates the programming unnecessarily.

FAST uses a batch fire system. It fires four fuel injectors at a time x 2.

The only disadvantage to that, if it is a disadvantage, is that for emissions reasons, you will have a minutely dirtier exhaust test.

That is because for a microsecond, there is unburned fuel laying on three other intake valves which haven't opened on the intake stroke yet and that unburned fuel can migrate to the exhaust valve in certain cam timing sequences.

So, therefore, individually fired fuel injectors are cleaner at idle and with US Emission standards, new vehicle manufacturers need every advantage they can get. That is why all OEM fuel injection systems fire the fuel injectors individually instead of in batches.

On a vehicle like the Pantera that is way over 20 years old, in the US, that simply isn't necessary. Batch fire is absolutely fine and as I see it, preferable?

The batch fire system that FAST adopted was actually designed by Bosch. It isn't a haphazard design. Just not optimal for new vehicles with strictly controlled exhaust emission requirements.

Performance wise, i.e., maximum power/go fast, there is no difference between individually fired and batch fired systems. At some point around 3,000 engine rpm's the individually fired fuel injectors can not keep up and start to work as a batch fire system.

So really those are the differences in the two available aftermarket EFI designed systems right now.

I have heard from certain self qualifying experts that they wouldn't be caught dead using a batch fire simply because it is the older design and not sophisticated enough for them to put their stamp of approval on it. So be it.

I don't argue. NO ONE is perfect! I realize that even if they don't. Sometimes very "bright" people can be very difficult to live with. I try to give them space.

The fact of the matter is that all things being equal, the simpler system by definition has to be better.

Anyway, that's what I know about what is going on with converting to EFI INDIVDUAL RUNNER aftermarket right now for whatever that is worth.

Again, the technology has just changed significantly within the last few years and those old systems like the Haltec are now just historical markers in the progression of better technology.

I'm just trying to help and sometimes the simplest things need to be stated. I'm not highly intelligent, just highly experienced.

Last edited by panteradoug

Ah. What I did?

My solution evolved from using the Weber 48 ida carbs.

I drilled and tapped into the carb mounting flanges. On the Hall manifold, they are very thick. I threaded in a -3 JIC male to 1/8"NPT adapter. Then used a -3 JIC T fitting running 3/16" stainless brake tubing from port to port. Flared tubing ends with tubing nuts and ferrels.

At the time there was a Mr.Gasket fuel log that fit in nicely just at the back of the intake manifold, near the top of the bell housing. There is a picture here of it installed that I included but you really can't see much of it, but that was my thinking, i.e., to minimize everything.

I ran the left side tubing to the left end of the log. The right side to the right side of the log.

This gave me four 3/8npt ports on top to use as vacuum accessory connections. I tried to use it as a vacuum source for the power brake booster but the IR system doesn't produce enough volume of vacuum for the brakes, but it is fine for a vacuum gauge and now is used also for the MAP sensor.

I'm using a Compcams vacuum pump for the brakes so there is no issue with not enough vacuum now.

On my set up, David's vacuum block would be in the way of my throttle linkage and using the Hall Pantera intake manifold, it has a cast in throttle tower for the throttle pivot.

It looks like you are likely already comited to using the ports drilled into your intake for the NOS but you can eliminate the vacuum block and gain some much needed room?

Here are some pictures. The top view is of the original setup with the Webers which I replaced with the throttle bodies. The vacuum plumbing is still there. The throttle connections are essentially still the same.

You can see a portion of the vacuum tube plumbing with the t-fittings which will give you a pretty good idea what they all look like.

The large -10 Hoses in the view from the top picture were removed. Those were initially intended for vacuum for the power brakes but that didn't work out.

The thought on the top picture was never to illustrate the vacuum plumbing. The combination of all of these pictures should give you an idea of how I try to tuck everything in.

The pictures would suggest that there is miles of space to work in and run hose and tubing, which really is the farthest thing from the truth in actuality?

I hope some of this helps?

With the FAST system, the CPU automatically compensates for the A/C compressor running and raises the idle speed, so with it I don't need an idle air control system separately. The combination of the sensors tell the CPU that the A/C is on and to raise the rpm. I think the number is it raises it 75rpm? Offhand I forget the exact compensation, but it works and it is adequate, and one less additional device to add onto something there is no space left for?

That's fine by me.


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Last edited by panteradoug

Thanks Doug.  The photos and your descriptions are very helpful.  As you mentioned the nitrous plumbing has already provided vacuum ports for both MAP and IAC.  Therefor I might as well setup both since Holley supports them.  In fact, the Holley setup wizard says that IAC is required although I can also see that it can be disabled.  

Pre Drive-by-wire, I mounted my throttle bellcrank on top of an IPSCO vacuum/MAP sensor housing. For a throttle return spring, I used a clock spring mounted on the underside of the bellcrank. You can see it in one of the attached photos. Most two bbl throttle bodies, including TWM, have a single common vacuum port, which is why I only needed four fittings on the housing.



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Last edited by davidnunn

When I started down this road (some may describe it as a rabbit hole) there was for practical purposes only the Hall manifold available.

Much of the plumbing choices were because of the idiosyncrasies of the manifold.

What you see is ultimately my solution for the Pantera. I had the same Weber setup on my 68 GT350 and everything was different.

The manifold that David is using changes it all again.

Incidentally, I still consider this all fun and not a burden as some would suggest.

I have been working with Jon Haas offline and he said that using soft plumbing to the MAP sensor is helpful because it dampens energy pulses from the intake.  Thus, I may try using 3/16 rubber vacuum line connected to a fitting like the one pictured above.  The runners on my manifold are already drilled and tapped for nitrous and the fitting might simply screw in.  The lines would tee towards the firewall.  The Holley ECU has the MAP sensor built in and the combined vacuum line would extend and attach to it.

If I went with IAC, it could be plumbed the same way and not difficult to try it.  Since the air (controlled vacuum leak) provided by the remote IAC is not affected by pulsing, I could make it with hard brake line.


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Last edited by stevebuchanan

Steve, please consult with Holley but I'm quite sure they will tell you, the hoses from the eight runners must all terminate in a common plenum. This is to absorb the pulses from individual cylinders. A MAP sensor doesn't work properly if the signal pulses. Rubber hose alone won't be enough. An IR intake is a very different animal from a single plenum type of intake. How large that plenum needs to be is a topic of debate. You saw the size of mine. The IPSCO one is 3 x the size. The one Borla casts into the base of their manifolds is 10 x the size but you can run MAP and IAC in the same plenum. Here's a photo of an Inglese plenum on a Hall Pantera manifold. I'm also told, the hoses from the port to the plenum should be as short as possible, so a remote plenum isn't a good idea. The theory is, you want the vacuum signal reaching the MAP sensor to be responsive yet pulse free. I know; sounds impossible! Oh, and the hoses should be the same length. Prior to my Holley Dominator ECU, I had an Accel Gen 7 and Accel told me I needed a plenum with a one liter capacity. I ignored that recommendation but it appears Inglese did not! 



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I have been working with Jon Haas offline and he said that using soft plumbing to the MAP sensor is helpful because it dampens energy pulses from the intake.  Thus, I may try using 3/16 rubber vacuum line connected to a fitting like the one pictured above.  The runners on my manifold are already drilled and tapped for nitrous and the fitting might simply screw in.  The lines would tee towards the firewall.  The Holley ECU has the MAP sensor built in and the combined vacuum line would extend and attach to it.

If I went with IAC, it could be plumbed the same way and not difficult to try it.  Since the air (controlled vacuum leak) provided by the remote IAC is not affected by pulsing, I could make it with hard brake line.

I found a place to mount the CPU right over Jon's Ignition Controller on the firewall.

I personally think that there is a degree of experimentation with all of this? Just finding places to mount things alone can be a challenge and keep in mind that you want to be able to access or service these parts as easily and simply as possible.

Lots of things want to occupy the same space.

I think that all you need to do with the MAP connection is connect it just like you would a vacuum gauge. What it is doing is telling the CPU electronically what a vacuum gauge is telling you. That part isn't rocket science.

Mine wound up with a rubber hose to run the connection to the back of the engine where my vacuum manifold is. For me, these were the best locations for all considerations.

It is up to the software in the CPU to interpret what the engine needs and is doing. Not you.

It is the interaction of the various sensors and the software of them to make the instant changes. That's what the software is all about.

The software for an 8 stack IR system is a different program then a single 4v plenum intake.

You cannot make an 8 stack IR manifold work the same way as a single plenum intake. Adding huge plenums is attempting to turn the IR into a single plenum manifold. It can be done, but what is the point? Then it is no longer an IR manifold?


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Last edited by panteradoug

Thanks David and Doug.  I spoke with Holley tech support this morning and he said to make a plenum to help dampen the energy pulses for the MAP sensor.  For IAC he said there is no similar need and it can be plumbed in series.  He said to definitely utilize IAC.  I placed an order for the Terminator X, Dual Sync distributor, remote IAC, MAT (manifold air temp) sensor, cable from ECU to Windows tablet, etc.  

Holley EFI has an excellent tech support web site with many, many users. It's structured as a Forum, just like this site. Holley tech's keep an eye on it and jump in frequently. You can find answers to just about any question you might have. In fact, it's frequently quicker to post a question there and wait for a response, than it is to call Tech support. 

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