MGB Air Dam

I am continuing to stay busy in the semi-heated garage, waiting for the last of the cold to move off. Now that we are in March, I know our nice weather donut-hole is coming, so some outside stuff is right around the corner. After cleaning and re-organizing some of the shelving in the garage, I decided to look at air flow at the front end of Oliver.

Farewell Victoria British

The world of auto-parts resellers got one business smaller at the end of 2020 when Victoria British (VB) was sold to Moss Motors. This is sad in 2 ways: first, one fewer option now exists for finding some increasingly hard-to-find parts and second the typically most expensive vendor (Moss) was the recipient of the old VB traffic. VB was a little old-skool, leveraging paper catalogs and a paper-catalog styled website experience. You could leaf through an online version of their catalog and click on the underlined part number to add it to your cart. It was very unusual and the pictures may not have been as hi-res, but it really had an old paper catalog vibe. I really liked it, actually. Back in the day, it was leafing through catalogs like this that gave you ideas. As to the sale, VB became a subsidiary of Long Motor Corp somewhere along the way, so I guess it was inevitable that they would be spun off since Long Motor focuses on US made cars (LMC Truck is their one big subsidiary).

Anyway, when I learned that VB was getting sold to Moss, I hit their site to find something unusual that Moss did not typically offer before they shut down. In retrospect, I regret not buying a T-shirt or a sticker while I had my cart open. I greatly preferred VB over Moss; did I say that already? There are a few alternatives still out there, but I suspect Moss will be getting more of my MGB repair money than they used to.

 

I found an ABS front air dam on the VB site for about $130US (I just looked and Moss now offers the exact same dam for... $165US). It is designed to hide under the big front rubber bumper, collecting the air from most of that span and routing it through the front apron and then the bottom end of the radiator. If your MGB shipped with (and still has) an oil cooler, this air dam would route this air through that as well. 

Directing Air

Running along the underside of the MGB rubber bumper is a curved steel section (the "front apron") with 2 rounded rectangular holes in it. Usually, there is an oil cooler behind the apron, and some cardboard air routing material so the air exhausting from the oil cooler routes into the lower few inches of the radiator. Oliver (my MGB) had his oil cooler removed by a prior owner (PO). Most of these little British cars do not require the oil cooler unless you live in a very hot part of the world (like Arizona, eg). Since the oil system does not have a thermostat on it, your oil will always route through the cooler, potentially over-cooling. At least, that's what I have read. I never had the oil cooler. I also never had the routing material to get the air passing under the bumper to direct into my radiator. I figure that cuts almost in half the amount of air naturally flowing through the radiator without the fan assist. In the picture on the right, the apron is on the left side and just behind that orange tow safety hook is the side of the radiator: note the 6-inch gap between.

Replacement plastic panels for the span between the apron and the radiator appear on the Moss site, for $70US (part number 475-255) to $90US (475-245), depending on your model. I was not sure either of these were the part I was looking for since the diagrams were not very descriptive. Besides, I had the day, I was snowed in, and the hockey games were not starting until later. I also recognize that oftentimes these universal-fit plastic panels don't fit without cutting and trimming. So, I decided to custom make one with some zinc-coated HVAC metal I had lying around.

Cardboard then Zinc-Coated HVAC Sheeting

I followed the tried-and-true path of building a model with some corrugated cardboard. First, I defined the rectangular bottom: about 18-1/2 inches wide by about 6-3/4 inches deep. This places the panel firmly against the rear-side of the front apron and less than half an inch in front of the radiator (see the picture on the side here). I did not want it touching the radiator, fearing that it could rub/cut through the bottom of the radiator eventually, causing a leak. Then, I modeled the sides, with a 90* turn out to support it from the top and a 90* turn in the other way to mate to the rectangle. The model was fairly straight-forward, but I found the pitch interesting. At the radiator end, it is about 1-1/2 inches tall, but at the front apron end, it is more than double that height. In looking at the front of the radiator, though, there is an air gap above the front-to-back support rails, so this air router thing will not be further compressing the air on its way through.

Once I had the cardboard model assembled, I tested my fit, and verified my plan to have the sides bolted to the front-to-back supports first, and then use sheet metal screws to hold the lower panel on. I transferred the design first to paper and then to HVAC sheeting. In the translations, there was some loss of fidelity, and I had to tweak/cut a couple of things, like the position of the mounting bolt holes. Still, I believe the end result will hold together, and will correctly route the air from the front apron to the radiator. Springtime testing will prove that out. Had I not been frozen into the garage, perhaps I would have cleaned up and painted the backside of the apron. Looking at it in these pictures... well... it does not look it's best.

Only 7 Screws

The ABS front air dam delivered in typical quick time from VB. I popped it onto the front apron after unpacking and immediately forgot about it. When I say "popped on", I mean I simply stuck it on there without any fasteners. I wanted to see how it looked and I didn't really have a place to store it in the seemingly-always-crowded garage. It gripped the front apron so well, it sat there, holding on, for weeks before I accidentally kicked it and it fell off. I think that if I hadn't kicked it, it would have sat there until I got to solving the air routing I just described above. Perhaps that is why these air dams ship with only 7 screws to mount them, without instructions, and without a clear reference for where the screws should go to best hold your dam in place. In Moss' defense, they have downloadable install instructions. Perhaps they were on the old VB site too. I don't know and their site if gone now. Sadness. Regardless, I stuck the IKEA-like drawing on the right, here, so we have a common reference point.

VB offered the fasteners, so I got them as part of that order. They are black-headed bolts (not screws as described in the Moss directions) with a nylon lined locknut as well as a black cup washer for the bolt head to seat nicely in the air dam. Between the black head and cup, the fasteners disappear into the dam. I looked at the Moss directions, and at least on my MGB, they will not work. I put blue painter tape in the spots where the directions indicate the holes should go and attempted a test fit. The holes on the ends would be up under the bumper, and I cannot get a drill nor screwdriver in there. So, I decided to go my own way.

I held the air dam against the front apron, and I could tell that my apron was not 100% square. Maybe Oliver had himself a little bender or the dam got hooked on a parking curb along the way. Regardless, I centered the central vertical on the dam with the center vertical on the rubber bumper. Once I had center, I considered where I had steel from the apron immediately behind the dam near the big air holes and there are plenty of options: above, below, and on either side. I ended up with a plan that was influenced by the Moss directions.

Dam'd

Using blue painter tape, a ruler and some calipers, I carefully made marks for the holes so they were the same on both sides. I put a hole about an inch inboard of the outer edges on either end, but down near the top-to-bottom mid-point. It is the same distance from the top edge as my planned center bolt, which is also equadistant top-bottom between the bolts I set to the outside of the 2 center air holes. This was the great deviation from the instructions: putting 2 bolts, stacked vertically on either side of the air holes approximately where the drawing only had one. The 2 extra bolts were taken from the top edge in the Moss directions which appear about 4 inches inboard from the end bolt/screw. I suspect the reason for those bolts being placed there was to reduce chatter by the air dam at speed. With the bolts all the way snugged down, the dam seems fairly secure. Still, if it gets bad enough, I can try to add 2 screws up under the bumper where the directions say, I suppose. I would need to remove the rubber bumper to do it, though. So, I am not terribly excited about it. Perhaps a thin strip of Velcro would suffice.

As I write this, the cold rain and snow have passed, and we are starting to enjoy calm, drier weather again. Soon, I will test-drive the air dam and air routing improvements, though I do not expect any meaningful/measurable change. This is just putting things in order as they were before (sans oil cooler) plus a little dress-up for the otherwise non-descript front apron.

Thanks, as always, for following along-