Inside Spaghetti Menders Wiring Systems & Technology

Wiring is usually the last thing an enthusiast thinks about when building a new race car. And – it usually shows. Bundles of unlabeled wires, shorts, difficulty starting, and electrical gremlins usually show up when the car debuts, or soon after. Even if not, the wiring being an afterthought usually comes back to bite the racer at the worst possible time… race day. One man, Bob Lapp, made a vow a lot time ago to fix this disaster once and for all by designing, building and selling turn-key, cutting-edge, simple wiring systems for race cars. His company is named – most appropriately – Spaghetti Menders.

Tracing back through someone’s wiring job can be a headache. Pull back on a race car’s dash and often all you find is black wiring from an obvious single spool of wire. What is ground, power, or even what goes where — sometimes even the owner doesn’t know. Hopefully, this can be avoided from day one with a correctly engineered and installed system.

We followed along with Bob as he designed and wired up a system for our infamous 1978 Malibu – aka Project Grandma. Grandma sports an Edelbrock EFI-powered 555ci Crate engine built by Pat Musi.

Spaghetti Menders: A Wiring Company is Born

“I use to be part owner of a company that use to wire fire trucks and ambulances, that required massive amount of wiring,” says Bob Lapp, owner

“We used the old relays with the plug-ins on the bottom that we use to bolt to the firewall. In the process of working on the car, one of the workers hit a wire and ripped it out of the bottom of the relay. What happened was that the car took off and the fuel pump shut off. Mix that with the nitrous that was still on and then the hood disappeared.

The question came up, ‘How do we keep from this happening again?’….This is where we came up with the concept of sealing the relays in epoxy. We used the computer cables on the emergency cars, so that was easy.”

Understanding Spaghetti Menders Wiring Philosophy

When we spoke with Bob Lapp, he explained to us that there are three core goals when it comes to wiring a car:

  • Organization
  • Simplicity
  • Reliability

Spaghetti Menders has done a great job incorporating all of them. Moving into their tenth year in 2010, each system has been designed vehicle specific. The team takes into account all accessories being used in the car and if it is turboed, supercharged, nitrous-fed, or naturally aspirated. This helps determine if you will need a circuit for your bilge pump or a timer for your nitrous kit.

Each system is broken down into different modules in the vehicle, with a central “hub” joining all of them together. For example – for our Project Grandma, we have the needed components for our Edelbrock nitrous system but also provisions built in for a supercharger that we plan to add later. For our application, the relay boxes are broken down into dash, motor, switch panel, and trunk.

Spaghetti Menders designs their circuit boards for their systems in house

From the left, the top and bottom posts are the power and ground to the relay box. The green middle connector are inputs. The 9-pin cable is for trigger sources to the switch panel. The rest is a five circuit relay that independently contain one relay, yellow light to indicate a working circuit, green activation light, fuse, and power output post.

The Relay Boxes

The magic of the system lies in the heart of the relay boxes, and that is the lack of wiring. By the slim profile, you can image how impossible it would be to run that much wiring, and that is because everything is controlled by a circuit board. Each relay box also has one main battery and ground input from the battery that is attached to the side.

“The main concept behind it was to get the high power closest to the device,” Lapp remarked. “Then by using the computer cables, it is signaling the relay on and off, which can be any length and small wiring. It only requires 250 milliamps to trigger the switch which is why it can be that small.”

Bob was the first person that used computer cables and relay boxes together on race car wiring and it has proven as a viable option. These posts also serve as a constant power/ground source for all associated electronics.

The switch point power for the electronics is done through a smaller post on the opposite end of the relay. Between this post and the relay is two lights (yellow and green) plus a fuse. The yellow light closest to the relay tells you that power is getting to that circuit properly. When you activate the switch, the green light will eliminate, if it doesn’t, the fuse is blown or the relay is bad. Pretty simple right?

Each relay box comes clearly labeled for what goes where

Inputs and Switch Points

Each relay box also contain 3-5 wire inputs between the positive and ground posts. These inputs can do a variety of tasks. For example our nitrous relay box, we inputed the trans-brake, and carb-mounted activation switch. The trans-brake input serves as an interrupt while the nitrous will not activate unless it sees the nitrous activation switch. There is even an input that comes from the fuel pump relay box that will cut power to the nitrous relay box incase of pump failure.

“The inputs on the relay boxes is where we need that other real world data coming into the car,” Lapp stated. “For example, we can run the intercooler pump input in the trunk, versus having to run it all the way to the front of the car.” Each of these inputs also have an LED to ensure it operates correctly. Generally, a three pin input is used in which the center pin feeds power to the first and third pin inputs.

The switch points for the relays are distributed through the computer-like 9 pin cables. Each relay box feeds those cables back to a central “hub”, (dash, motor, trunk) and distributed to the switch panel via a 15 pin plug. “Depending on what you need, the interface box talks between the relay boxes and switch panels,” Lapp says.

“The interface modules allow for expandability of the system. This is where we make a decision of what kind of application it will be. A supercharged application uses the same relay boxes as a nitrous one, they are just told to do different things.” Since switch points are low amperage, these small diameter wires are more than suitable. The panel then turns on the respective device correctly, since these are all pre wired before you get it.

The central “hub” where all the switch points come together from the car. Instead of wires running up and down the middle of the car, it is just these cables

Only one 15-pin computer cable connects to the switch panel that comes pre-engineered specifically to your application

Everything Goes to the Battery: The Theory of Floating Grounds

Spaghetti Menders utilizes floating power and grounds, meaning the power only draws directly from the battery (and not piggybacked to other sources) and all the grounds route to the negative battery terminal and not to the chassis. This locates a bulkhead fitting into the wire wall to supply power for the front/cabin relay boxes as well as the starter.

Each electronic connection that requires a power source or a ground is routed to either the bulk heads or directly to the battery. Not only does this keep wiring cleaner, it also guarantees a strong enough power and ground source for everything wired in. Another aspect is data logging and sensor read outs; daisy chained power sources and chassis grounded points can cause interference that can keep these from operating correctly.

Bulkhead fittings safely transmit power and ground through the firewall, offering pickup points from the battery on each side

The main components laid out

Installation Highlights of our Spaghetti Menders Control System

The system in our Malibu is typical for an EFI Big Block with a single state nitrous system. However, we also have added provisions for an intercooler should be add a supercharger or turbocharger in the future.

Luckily the “Chief Menders” of the Spaghetti, Theresa and Bob Lapp, were able to make it to the powerTV garage to help us with the installation. Also since we didn’t want to run an alternator, we went with a dual 16-volt system.

Let’s take a look at some of the installation highlights:

Dual XS Power Batteries (S1000) that are 16V provide the voltage to the Spaghetti Menders system. Spaghetti included a dual battery kit that includes all connections, battery cables, and charging lugs to make setup simple and easy. Just measure, cut, and install.

First course of action was to get the electronics mounted where we wanted them. As we installed them, we labeled all the wires so we knew later where they needed to go. Bob started with the battery terminals and remote shutoff switch first. The charge plug for the batteries was placed in a cutout through the license plate.

Bob frequently has to advise people where to run wiring in the safest area possible. You want to try to stay away from heat, fans, headers/exhaust, superchargers and other danger areas that could sever wires. We ran our wires under the front roll cage extensions.

Here we mounted the front Spaghetti relay box that would control the lights, engine controls, fans, and water pump right by the front fender. It was mounted on a tab to the left of the radiator.

Bob then uses screw in c-clips to run the wire underneath the cage for a clean fitment. Power, ground, input cable, and the nine-pin cable are the only wires we need to run in there. The remaining wires will go to head lights, park lights, electric fan, and water pump. The input wire will go to our bump start (driver and passenger side) for adjusting valves on the fly.

Mounted to the rear mini-tub was the relay box for the fuel pumps, batteries, intercooler, rear lights, etc.

Spaghetti’s custom control box.

Here’s our wiring job half way through in the rear of the car. It looks a little intimidating, but you need to remember: one wire at a time.

More Junk in that Trunk

Our relay board in the trunk housed two fuel pump outputs (though we only have one, hence the loop), rear parking lights, brake lights, and intercooler pump (for when we add a supercharger). Our inputs included one for the intercooler pump and a master kill switch to disable the fuel pumps if the kill switch is turned off. Above the large board is a smaller one that is designed for our nitrous fuel pump. A secondary switch panel is used and this will only activate the nitrous pump when you need to. Also, when we go to the supercharger, it will be easy to remove the nitrous accessories.

We removed the dash in order to run all of our wires cleanly and neatly. With the Spaghetti system, wires really do not need to be nearly as long as in a traditional style control box. Since we have relay boxes in the engine compartment, interior, and rear trunk area, wires longer than 8 feet are rare.

The interior is where we run into our largest amount of wiring. A slew of Auto Meter gauges, MSD 7 ignition box, Pro-Flo XT ECU, and other accessories all needed to be routed accordingly. For low amperage electronics – like our gauges – we ran to a power junction block (picture above the Auto Meter tach) to tie these together on one power source.

Wiring for the ignition box and ECU get their own power sources. Our relay outputs for our under dash relay box included motor start, ignition power, dash lights, computer power, and line lock power. The inputs on the three pin included another bump start switch and neutral safety switch. Below the relay box was our Spaghetti Menders nitrous timer and dedicated relay box. After two days of wiring, we were buttoned up and ready to roll.

Spaghetti’s Top Five Wiring Tips

1) Label Everything — It is hard to remember where each wire is ran in your car. Label the wiring at any junction point, at the contact. This way if you ever run into wiring problems down the road, it will make for a lot easier process on tracing it.

2) Correct Size Wire —
Ignition boxes draw more amperage than gauges do. Make sure that if wire extending is needed, to lengthen the wires with the manufactures recommend gauge. Also keep in mind that some contacts require special wire, like a shielded cable to help eliminate electrical noise.

3) Color Code It – As mentioned above, if wire extending is needed, stick with the same color. Don’t have a yellow wire coming out of the ignition box that is connected to a black wire. This is going to make your life hell when it comes to finding a problem.

4) Mending Connections + Shrink Tubing – Different people and manufactures will either tell you to use socketed/crimp connections or solder connections. Some say soldering can cause interference through the metal and others say butt connections fall apart too easy. Ask the manufacture what they recommend for their component. Either way, use shrink tubing. It will help product soldered connections from grounding out. For crimp connections (like ours) it helps keep the bare wire at the end of the plug from grounding out and it also helps hold the wire into the connector.

5) Double Check Your Connections – This is simple, just sometimes time consuming. Double check all your connections when you are done. Not only test the connection to assure it is tight, but also the wires are going the right way. Having polarities swapped backwards on an electronic is not only the easiest way to destroy it, but potentially burn your car to the ground.

The Final Results

It took Bob about 16 hours to completely wire our 1978 Malibu from start to finish, including the time to take breaks to shoot photos and video. The end product was stunning – clean, logical, and simple. What once started out as a heap of wires, boards, and spools ended up as an organized electrical system.

Spaghetti Menders offers a top-shelf wiring system that is customized to your application for your exact race car. Basically – they do the hard work for you in terms of designing how the system will operate. All you really need to do is install it – and trust us – with Spaghetti Menders – this is the easy part.

Once we were completed, we decided to fire up our Malibu! Hopefully you’ll enjoy the fine sound of the Edelbrock/Musi 555 as much as we did! Thanks Spaghetti Menders!

About the author

Mark Gearhart

In 1995 Mark started photographing drag races at his once local track, Bradenton Motorsports Park. He became hooked and shot virtually every series at the track until 2007 until he moved to California and began working as a writer for Power Automedia. He was the founding editor for its first online magazines, and transitioned into the role of editorial director role in 2014. Retiring from the company in 2016, Mark continues to expand his career as a car builder, automotive enthusiast, and freelance journalist to provide featured content and technical expertise.
Read My Articles

Late Model LS Power in your inbox.

Build your own custom newsletter with the content you love from LSX Magazine, directly to your inbox, absolutely FREE!

Free WordPress Themes

We will safeguard your e-mail and only send content you request.

LSX Magazine - The Late Model GM Magazine for Camaro


We'll send you the most interesting LSX Magazine articles, news, car features, and videos every week.

LSX Magazine - The Late Model GM Magazine for Camaro


We will safeguard your e-mail and only send content you request.

LSX Magazine - The Late Model GM Magazine for Camaro


Thank you for your subscription.

Subscribe to more FREE Online Magazines!

We think you might like...

Classic Chevy Magazine
Drag Racing
Engine Tech

LSX Magazine - The Late Model GM Magazine for Camaro

Thank you for your subscription.

Subscribe to more FREE Online Magazines!

We think you might like...

  • chevyhardcore Classic Chevy Magazine
  • dragzine Drag Racing
  • enginelabs Engine Tech

LSX Magazine - The Late Model GM Magazine for Camaro


Thank you for your subscription.

Thank you for your subscription.

LSX Magazine - The Late Model GM Magazine for Camaro

Thank you for your subscription.

Thank you for your subscription.