Emboss

We have a winner Got around to checking on my car, and yep, the ducts end pretty much right in front of the manifolds. So the effect will be to blow cold air front-to-back along them.

Jerry Feather

Here I am. I just read this thread. I have one of the aftermarket aluminum belly pans that I have not put on my car yet so I could possible develop from that. Rob, the templates you have in this thread show up merely as red X's and do not enlarge to anything I can see. I'm not sure wqhat I need to do to open them up. MNaybe you could email them to me and I could print that out and have a look at it.

I have actually given some thought to finding a used belly pan on ebay and trying to develop the scoops from what might be left of that. I have seen pictures of the scoops, but haven't studied them carefully. I'll get a look at them and perhaps give it a shot.

Thanks for the suggestion.

jfeather@bresnan.net

Jerry Feather

Jerry Feather

Rob, I guess my computer was just taking a while to load the pictures,. They are now shown in your post so I can see what you have put a lot of effort in on this. Thanks.

Jerry Feather

Rob Edwards

The University's webserver here goes on a coffebreak every morning for an hour or so. Not sure why but pics often don't load between 6 and 7 here.

Jerry Feather

I've been looking at Rob's pictures and at my belly pan up on the shelf in my garage. From what I can tell and from the suggestions here, if the ducts are in front of the exhaust manifold, then I think I would agree that at least part of their purpose is to blow cool air onto or into the exhaust header area. That air is however, being blown straight up and not back .

It looks like the larger of the two ducts, the one on the right, has an additional purpose and I have to guess that that is to blow cool air foreward, perhaps onto the AC compressor. Otherwise I can't figure out what the square opening is that is cut out and bent up like a flap on the front of that duct.

In terms of fabricating these, it looks like the back of them is common to both. The fronts are different and match up to the different parts of the NACA ducts fabricated into the belly pan itself. One match-up point is a little wider than the other.

I think the backs of these can be formed out of aluminum, probably 3003 T11 in about .032 thickness. The fronts might also be made out of the same material, of they might be made out of ABS plastic, (which I have been accused of having a fetish about). However, out of aluminum, the front parts might be formed or fabricated in either a weldment or riveted up in pieces that are partly formed by bending rather than compound forming like I envision the backs being done.

Just some thoughts. Any other ideas?

Jerry Feather

Jerry Feather

One thing that strikes me as odd about these ducts is that the air outlets on the top of each is pretty small in respect to having a general purpose of blowing cool air into the exhaust header area, and they also seem to be fairly directional specific. In other words it looks more like they are intended to blow air onto something more specific than just onto the headers. I suppose one will need to put a pan on and see just exactly what the air might be aimed at.

Has anyone taken a closer look? Does anyone have any pictures of the pan installed with these ducts, and perhaps from above if they can be seen and photographed?

Jerry Feather

Jerry Feather

I wonder if perhaps this might be the best answer about the intended purpose of these ducts.

Why would you need that little bit of air directed at the exhaust sustem?

With the motor mounts being rubber, and most (?) or all (?) filled with liquid, and with them living in a fairly hot enviornment, cool air onto them would tend to make them last much longer, I would think.

Jerry Feather

Dictys

i wonder what the life of the motor mounts are with and without the original belly pans fitted and if there is a significant difference or not.

dr bob

Outlet is directed at the motor mounts. There are heat shields between the exhaust and the mounts, but the shields merely slow the migration of heat. It's a relatively dead area for airflow, so any little breeze from these ducts will prolong the life of the mounts. The ducts themselves are a little too complex to make as one piece plastic except as a blow-molded bit, and the proximity to the exhaust pretty much rules out plastic anyway. While it might be possible to hand-form the separate pieces in aluminum, production would be rather slow.

My borescope is on turbine inspection duty on the east coast right now. If I have the car up this weekend I'll snap a few regular camera pictures. But, you can easily see the relative locations of the speed nuts on the little brackets just below forward of the motor mounts on the crossmember, where the screw fastener inside the duct holds the belly pan in proper position.

SQLGuy

Very interesting! So there may be a relation between the number of cars missing the undertray and the number of cars needing new MM's...

Jerry Feather

I would guess that the motor mounts suvive just fine when there is no belly pan. There is likely enough air circulation around them without the pan to ensure that they do not soak up any heat. However, when the belly pan is installed that is probably where the concern came about for the motor mounts since the circulation of air has been substantially eliminated--hence the addition of the little vents aimed at them on top of NACA ducts in the belly pan.

Therefore, there is probably a relationship between the cars with the belly pan but without the vents on top of the NACA ducts and those in need of motor mounts.

I think what that says is that you should be sure to have the vents added when you put the aftermarket belly pan on. Those who want the belly pan and don't have the vents, might be the market for the vents.

Jerry Feather

Jerry Feather

Dr Bob might be right about the plastic version of these vents. I think they can be made out of aluminum and formed much as the originals are. I think the only difference is might be a slight difference in the shape, and they would likely be riveted together, front to back, rather than spot welded.

I'm not sure yet just what the forms might be made out of. I'm thinking the female aspect would be steel, probably angle iron, and the male part also steel but with perhaps hardwood, like oak, for the form itself.

Jerry Feather

Jerry Feather

Hi Tom. I guess you noticed that I am in fact out here in ciber world where I guess I belong. I think you are right. If these vents (I am calling them) were not on my "list," and I think they might have been already, they are now.

I picked up some scrap angle iron today at the scrap yard that I think will be some good basic material to make the forming machines for the aluminum parts of these vents.

I am dealing with a little physical problem right now that is going to limit my ability to work standing up for very long, so I may not get to these items very soon or very fast. Too, many of you know that i have some other very pressing projects to get done first.

Nevertheless, my brain is always happy to have some more creativity to deal with.

Rob, there is one important measurement to deal with that you have not shown in your excellent pictures and templates. They are really, really, valuable in terms of helping me design tooling to make these parts. Do you have any idea what the measurement is?

Jerry Feather

Rob Edwards

Jerry-

Sorry, I'm sure I missed at least several important dimensions. But it occurs to me that the most useful thing to do would be to just stick the two ducts in a box and ship them to you so that you can have a 'real' pair of them to measure from. I'm in no rush to get them back, as long as they come back eventually. Shall I mail them to the Skyline address below your avatar?

Jerry Feather

Thanks Rob. You are my kind of guy. The avatar address is mine and will work. Thanks a bunch. Actually you only missed the one. The rest are really great. I will hold them in trust for return to you, with a set of new ones, if they come to pass.

Jerry Feather