Miller's Mule Blog » Projects

Fiat Coupe Airbox Project (Part 1 – Forming)

Jason — Sat, 04 Feb 2012 04:51:49 +0000

An airbox can make or break an engine. A proper airbox has to do a couple of things 1) provide cold air to the engine, 2) provide clean air to the engine, 3) provide enough air to the engine. It may seem simple, but it is actually a bit of a challenge, especially while trying to fit an airbox in a constrained engine compartment. Browse through the photos below to see how this project started to take shape! (Clicking the photos will provide more detail)

The first problem to tackle was to define the hard constraints such as the firewall, hood, carbs and overall engine compartment. I machined up the baseplate shown below as a reference plane.

Aluminum Baseplate

Once I had a plane of reference, I used expanding foam packing material to measure the clearances.

Instapak Mold

Here you can see the impressions in the foam.

Instapak Impression

Once I knew how much room I had to work with, I began to shape the foam form. I had to figure out the best shape for proper airflow, while also allowing access to the Webers for tuning. What good is an airbox if you can’t adjust your idle!

Foam Form

The form further developed, and I decided to place the inlet high in the engine compartment. This allowed for smooth flow from the inlet to the base plate, no bumps, no restrictions, no turbulence!

Developing Form

This is the final form the airbox took. The more I cut away, the more fragile it became, so I used masking tape and wooden dowels to hold it together.

Finished Form

The other part of the project was the filterbox. I wanted to keep the filter as far away from the carbs as possible, reason being, is that filters create a large amount of turbulence which is exactly what we are trying to prevent. This is yet another reason why those mesh screens on air horns are about the worse thing you can do to a Weber carb!

Filter Box Frame

Like the airbox, I had planned to build the filterbox from scratch. This turned out, however, to be very difficult. I decided to start with a BMW 850i filterbox instead. These are very well built, and filters are easily available. I would retain the lid and latching mechanisms but reshape the rest.

Filterbox Shaping

Simple, everyday cardboard was used to fill in the holes in the box, and shape it to something more useful.

Filterbox Bondo

The joints were sealed up with Bondo and sanded smooth.

Snorkel Shaping

The final step in forming the filterbox was to add the snorkel to draw air from the front of the car. The theory being that as the car moves along, the pressure at the front of the car increases with speed. If we’re lucky, we might even get a bit of a ram air effect and push 1-2% more air into the engine and push 1-2% more power out!

Stay tuned for part 2, fiberglass!

HTD Drive System Preview

Jason — Wed, 30 Nov 2011 19:49:12 +0000

Here’s a little preview of one of the projects we’re working on.

Fiat HTD Belt Drive System

This is a complete belt drive replacement utilizing 8mm HTD belts instead of v-belts. The load to spin up the alternator alone (not even charging) will exceed the power handling of a conventional 9.5mm v-belt. Overloading the belt can cause all manor of problems, specifically throwing/chunking the belt! Thus it is necessary given the acceleration of the engine and the load carried by the crank, alternator, water pump circuit, to make some changes…

Faded Interior? Nothing Carpet Dye Can’t Fix!

Jason — Tue, 12 Jul 2011 06:19:37 +0000

I finally got fed up with the state of the interior in my Integrale. The poor car looked as though it had rested under the sun for a decade. The carpet was a hodgepodge of dirt, stains, and a now baked-on protective film. Something had to be done.

First step was to strip the interior. Luckily my cousin Clif volunteered to help! Click through the gallery for full details!

Volumex Crank Pulleys

Jason — Thu, 16 Jun 2011 03:42:07 +0000

A while back we were contacted about designing a crankshaft pulley to suit a 2 liter Volumex supercharged Fiat engine. Our client requested an underdrive pulley with 60-2 trigger wheel and a cog belt drive for the supercharger. We went back and forth with a few design iterations. Should we use a new cog drive? What would be the best supercharger ratio, and ultimately cog drive tooth count? We settled on a final solution. Though we could produce a new cog drive, the pulley would utilize a 29 tooth OE cog drive. This would be mated to an underdrive crank pulley made from 7075 aluminum with our off the shelf trigger wheel.

A couple of weeks ago we finished the pulley, check out the results!

If you’re interested in a similar pulley, or just need dimensions for some of the OEM parts, shoot us a comment or email!

Wheel Polishing

Jason — Fri, 31 Dec 2010 04:22:04 +0000

I just came across an old video I made showing how we polish wheels, almost 200k hits, who knew?

[There is a video that cannot be displayed in this feed. Visit the blog entry to see the video.]

Parts Pipeline

Jason — Mon, 26 Jul 2010 04:39:42 +0000

I often get asked what I'm working on lately in the shop, well here's a preview of a few of the parts in the pipeline. These are ready to go from prototype stage to full production:



Fabricated crossmember. Unfortunately a decent crossmember is just about impossible to come by these days. The OEM units tend to crack where the control arms bolt on and a replacement replacement from the aftermarket is  poor quality. Our solution is to reproduce a stronger unit. While we're at it, we give you the choice of moving the control arm mounting points, for use with lowered cars. Its even designed to bolt on a steering rack!

Wide sump oil pan. How many times have you heard of people destroying their oil pans and pickup tubes? Our oil pan is not only wider but nearly 1.5" shorter for more ground clearance.

Tubular control arms. Finally ready for full scale production.

All aluminum cam pulleys. It is increasingly difficult to make cam pulleys from OEM cores. We figure, why bother, we can make our own from scratch.

Coil over suspension, see #3.

Hydraulic throw out bearing conversion kit. A necessity for changing clutch feel on high clamp pressure clutches.



Of course there are more projects but these are nearest to becoming off the shelf products.

MG TD Flywheel Lightening

Jason — Tue, 23 Mar 2010 05:18:23 +0000

In its original condition, this flywheel was in terrible shape and looked as though it had sat in a field rusting for 20 years. The clutch pins were seized and made of very poor corroded material. The grey iron it was cast from in the 50′s was porous and soft. The surfaces were not parallel and the diameters were not concentric! With a little machining magic though, it looked better than brand new.

Flywheel Lightening: $60
Balance: $40
Regrind Friction Surface: $40

Project M5 Cooling System

Jason — Mon, 18 Jan 2010 02:36:20 +0000

As a side effect of always working on customer’s projects, my own get ignored. Take, for example, my ’91 BMW M5. This car and I have been through good times and bad. Feeling neglected, the car decided there would be bad times in the near future. First, it did so by seeping coolant on my garage floor but only a few drips to nag me. A week later a hose clamp mysteriously destroyed itself. The next day, the engine started missing. After a month of fussing, the car had had enough. Just down the street from my home the water pump gave up and puked out all of the coolant. “Ruh-roh” I think to myself…

Lucky me, I thought ahead eight months earlier and I ordered all 17 hoses, a thermostat, gaskets, o-rings, etc.. including a new water pump. Now all I had to do was swap out some parts!

Needing a daily driver, I proceeded to rent a car: a top of the line Hyundai Accent. Bright blue. I figured at worst I’d only have to suffer three days in this car but I figured wrong. The next day the coldest weather in the last decade hit Houston and put the project on hold for a week. I decided to make use of this time and powder coat the coolant manifolds:

All said and done I think the project turned out pretty well. Everything is nice and clean, no more seeping coolant. I’d dare say the system is ready for another 100,000 miles and when I replace it then it will be much easier without busted bolts and corroded aluminum!