Delorean auto parts/ John Hervey hot air dam - How is it held into place?

[Mike C.]

Crazy question, I know. I have one sitting in my living room, and thought maybe I was missing something. On the pics on his website, It shows two little metal tabs holding the bottom of the air dam

http://specialtauto.com/delorean-parts/images/delorean-hot-air-dam-place.jpg

These lil tabs (which btw look like scrap pieces of hose clamp from what I can see) do not come with the air dam.

Last year at Celebration, it was 94 degrees and I killed a fuel pump on the way home. I wanted to make sure this year the same thing doesn't happen, so i'd like this installed, but I don't want it popping off on the highway.

Anyone have any tips on installing this thing? I also don't want air getting behind it, causing it to flap about, or worse... hum... lol

[DCUK Martin]

With advance apologies for not actually answering your question: The fuel tank gets hot because the coolant pipes run directly underneath it. It'll be worse on a hot day, yes, but has anyone actually taken any measurements as to the effects of the "air dam"?

[Mike C.]

With advance apologies for not actually answering your question: The fuel tank gets hot because the coolant pipes run directly underneath it. It'll be worse on a hot day, yes, but has anyone actually taken any measurements as to the effects of the "air dam"?

No apologies necessary, Martin. I was curious about this too, because it seems it would have been more beneficial to have that open to allow air in there, but people I talked to on the old forum swore it was the best thing to put on, since it was a popular issue.

[Spittybug]

Mine simply has 4 sheet metal screws along the bottom edge, going into the crumple thingy. Never a problem.

[Morpheus]

My first car had this dam, and I'm convinced that it helps keep the tank cool. I believe it was held in with screws along the bottom instead of hose clamps.

If you think about it, the theory makes sense. Prevent the hot FL air (which gets even hotter as it flows through the radiator) from blowing over the fuel tank which is resting on top of hot coolant pipes. Even if it makes a 5 degree difference, it helps.

[outatym2001]

That piece of metal is soft enough to bend into an ‘S’ shape. Now lay the ‘S’ down horizontal and it acts as two hooks combined into one.
One half of the hook supports the black rubber Hot Air Dam from below.
The other half of the hook hangs onto the lip / ledge of the forward part of the epoxy coated frame.

The length of the piece of metal is 10 to 12 inches (25 to 30 cm). You can find it in the plumbing section of your favorite hardware store.
I used that same soft metal to make a bowl shape to hold my one inch tweeters in place for my DeLorean radio speakers. I installed the tweeters where the original 3-1/2” speakers go under the dash pad.
Please see Hot Air Dam pictures below.
P.S. John Hervey should have included the pieces of metal with the Hot Air Dam at least he did with mine.

[Mike C.]

That piece of metal is soft enough to bend into an ‘S’ shape. Now lay the ‘S’ down horizontal and it acts as two hooks combined into one.
One half of the hook supports the black rubber Hot Air Dam from below.
The other half of the hook hangs onto the lip / ledge of the forward part of the epoxy coated frame.

The length of the piece of metal is 10 to 12 inches (25 to 30 cm). You can find it in the plumbing section of your favorite hardware store.
I used that same soft metal to make a bowl shape to hold my one inch tweeters in place for my DeLorean radio speakers. I installed the tweeters where the original 3-1/2” speakers go under the dash pad.
Please see Hot Air Dam pictures below.
P.S. John Hervey should have included the pieces of metal with the Hot Air Dam at least he did with mine.


Wonderful explanation. thank you very much. I was kinda wondering why i didnt receive the pieces of strap, but luckily I have a roll of it in my tool box. Definitely appreciate all the help!

[WelmoedJ]

When I bought my hot air dam from John while visiting him he was kind enough to also provide the strips that make up the clamps.
However I was not sure it would stay in place so I drilled a hole through each strip and into the front lower edge of the front frame extension.

Though we don't have really hot summers like in the south of the US even driving my car over there didn't heat up the fuel as it keeps the passing wind from going over the top of the fuel tank.

Martin however is also right that a lot of heat occurs at the cooling pipes on each side of the fuel tank.
We could do with some temperature insulation there as well since these pipes are closed in by tank and tank plate.
Any thought on the latter?

[rddmc]

8734Zip ties. Drill two holes in the hot air dam(heat shield) about six inches apart and 3/4 inch up from the bottom. Run two industrial strength zip ties through them and around the frame. This way there is no need to penetrate the frame with screw holes.

Rod
10921



















Crazy question, I know. I have one sitting in my living room, and thought maybe I was missing something. On the pics on his website, It shows two little metal tabs holding the bottom of the air dam

http://specialtauto.com/delorean-parts/images/delorean-hot-air-dam-place.jpg

These lil tabs (which btw look like scrap pieces of hose clamp from what I can see) do not come with the air dam.

Last year at Celebration, it was 94 degrees and I killed a fuel pump on the way home. I wanted to make sure this year the same thing doesn't happen, so i'd like this installed, but I don't want it popping off on the highway.

Anyone have any tips on installing this thing? I also don't want air getting behind it, causing it to flap about, or worse... hum... lol

[rddmc]

I also used two white nylon washers on the front side of the hot air dam (could not find black ones). I also drilled a hole between the zip tie holes and pushed a long fir tree through which rests on top of the frame lip. Both of these are probably overkill and unnecessary. My heat shield has been in place for several years and has remained secure.

Rod
10921

[Mike C.]

8734Zip ties. Drill two holes in the hot air dam(heat shield) about six inches apart and 3/4 inch up from the bottom. Run two industrial strength zip ties through them and around the frame. This way there is no need to penetrate the frame with screw holes.

Rod
10921

Excellent idea, Rod. Thank you. I happen to also have long industrial tie straps at my disposal. Supposed to get rain tomorrow, so I will be doing this on Thursday.

[SIMid]

Mine didn't have one, so I made one out of Dynomat, cut to shape and stuck on.

[Bitsyncmaster]

I tested the fuel temp that made my pump start to buzz and it was about 125 deg.F

So it would make sense to prevent air from the radiator that is above that temp from blowing over the tank. But then, your trapping any heat from the cooling pipes. So does the hot air dam help? I don't know.

I installed mine with wire ties. Just make a cut where you want to install a tie.

[lazabby]

I got some foam insulation used in wrapping pipes to keep them from freezing and put it on the coolant hoses that run next to the fuel tank. This keeps the heat from the hoses from heating up the fuel tank. You may want to try it.

[Nicholas R]

A place near me sells sheets of rubber in any thickness you want so I ended up just making my own hot air damn. I supported it the John Hervey way. I took 3 strips of aluminum plate, I believe ~1/16" and made hooks shaped like this:
http://img208.imageshack.us/img208/4118/airdamnhooks.jpg

[jawn101]

This may be a silly question, but how is the top of it supported?

[outatym2001]

This may be a silly question, but how is the top of it supported?

Those are some great alternatives for providing support from underneath the Hot Air Dam.
The top is not supported at all since there is nothing to connect it to. The Dam is just crammed into place against the fiberglass body and those clips on the bottom. The rubber is so thick and so big that I hope it doesn’t decide to fall out. If either of those clips on the bottom falls off then with every bounce the Dam will certainly slide down until it hits the road.
I like the idea of using zip ties the best since they won’t rust and the aluminum hanger is good too.

[jawn101]

Those are some great alternatives for providing support from underneath the Hot Air Dam.
The top is not supported at all since there is nothing to connect it to. The Dam is just crammed into place against the fiberglass body and those clips on the bottom. The rubber is so thick and so big that I hope it doesn’t decide to fall out. If either of those clips on the bottom falls off then with every bounce the Dam will certainly slide down until it hits the road.
I like the idea of using zip ties the best since they won’t rust and the aluminum hanger is good too.

That's what I figured. Those S-hooks made from hose clamp seem like they could bend under the weight of the dam, which would let it drop down. I'd want to find a way to attach it from the top somehow, but never having seen the part in person or how it fits in I don't know how you'd accomplish that.

[Bitsyncmaster]

My best guess as to what heats up the fuel is the return fuel line. The returned fuel is heated by engine heat. I measured it and the return line temp is 2 deg. F warmer than the supply line.

[whocruiser]

Had one on 1662 for 7 or 8 years held on by 2 hose clamps on the frame. Moved it over to 1150 when I bought it 18 months ago and punched holes for zip ties to be kinder to the frame. Either method will keep it securely attached. Before installing it 1662 had frequent fuel pump buzzing and ran through a new pump every year or two, after installing the air dam no more problems of that sort, and 1150 is still running well on the same pump it had when I got it (presumably installed by DMC Florida during the previous owner's frame-off restoration a couple of years prior.) For a daily driver in hot weather this is a must-do upgrade or you're just asking for trouble.

[David T]

The fuel in the tank gets heated several ways. Ambient temperature, being pressurized and passed through the PPR, the coolant pipes pass right next to the tank. Finally the airflow off of the radiator and condenser. If you have a kinked hose or dirty pick-up filter in the tank and the level is low it is very easy for the fuel to vaporize. And now with all of the alcohol/methanol in modern fuel it is even more prone to vaporize. Anything you can do to reduce this is good to do. There does not seem to be any downside to using the "heat dam". A lot of cars have one and no one has ever reported any ill effects. If you notice problems when the car is very hot or a loud fuel pump a heat dam is a good idea but I would also recommend going inside the tank and inspecting everything to be sure everything is in good condition and properly installed. I also like a spring inside the pick-up hose. When it gets hot it gets soft and that fuel pump can pull a hard enough vacuum to collapse the hose, starving the pump and making it noisy. Once it gets noisy it starts wearing out prematurely.
David Teitelbaum

[Chris_Von_Bron]

hi guys,
I would like to create a hot air dam (as well as try and insulate my coolant pipes) to help reduce heat to the tank during the hotter weather.

Sourcing neoprene rubber isn't difficult. What I'm curious about is the thickness. Too thin and it won't be effective enough and too thick will make it hard to fit, secure and add more weight than necessary.

What do you think the optimal thickness would be (Hervey doesn't show the thickness on his site and emailing him 12 days ago with the goal of ordering resulted in no reply). The site wouldn't let me update my address/payment details due to errors which I mentioned in my email to him.

Thanks in advance
Chris

[SS Spoiler]

I made my own hot air dam with some bailer
belting from a farm store. I think it was about a
quarter inch thick. Also works great for under the
car skirting. Beings that it's rubber and flexible it
just bends going over bumps, and still looks good
after28 years of driving....

[DrJeff]

hi guys,
I would like to create a hot air dam (as well as try and insulate my coolant pipes) to help reduce heat to the tank during the hotter weather.

Sourcing neoprene rubber isn't difficult. What I'm curious about is the thickness. Too thin and it won't be effective enough and too thick will make it hard to fit, secure and add more weight than necessary.

What do you think the optimal thickness would be (Hervey doesn't show the thickness on his site and emailing him 12 days ago with the goal of ordering resulted in no reply). The site wouldn't let me update my address/payment details due to errors which I mentioned in my email to him.

Thanks in advance
Chris

Hi Chris,

I just measured a Harvey air dam I have sitting around. It is 7mm thick. It has a ply in the middle of the 7mm thickness.

Jeff

[Chris_Von_Bron]

Hi Chris,

I just measured a Harvey air dam I have sitting around. It is 7mm thick. It has a ply in the middle of the 7mm thickness.

Jeff

Thanks guys,
Very interesting how you're both within a few mm of each other, quarter of an inch (6.35mm) versus the 7mm thick Hervey version.

I wonder what folded/laminated material was used for the ply in the middle? I guess we'll never know, but it's interesting to note (if I'm understanding you correctly) that a total dam thickness of just 7mm overall is effective enough.

Cheers

Chris

[DCUK Martin]

If the job of this "dam" is to deflect air flow under the car rather than over the top of the chassis, then it doesn't matter what it's made of or how thick it is, so some light aluminium sheet would be my choice... if I thought it'd make any appreciable difference, which I'm afraid I still don't.

It's one of those things that seems logical - like boxing in of the lower arms. And it isn't a matter of opinion - in this case it needs testing.

The main coolant pipes, being aluminium, have an excellent heat transfer capability, and they live in an enclosed space with the tank sitting directly on top, constantly pumping heat at 80-something degrees into that space by conduction. It's like a pan sitting on a stove.

But yeah, the dam is unlikely to cause any harm

[Chris_Von_Bron]

http://dmctalk.org/showthread.php?3763-The-Restoration-of-1768/page25

The above has been handy to show that it is possible to insulate the coolant pipes. I imagine that the insulating properties of Neoprene wrapped around the coolant pipes that run below the tank would help reduce the heat transfer from the pipes to the tank.

I've expanded on this via the following new topic:-
http://dmctalk.org/showthread.php?16316-Fuel-pump-noisy-when-been-in-traffic-for-over-an-hour&p=232319#post232319

I'm keen to explore as many areas as it takes to resolve this.

[DCUK Martin]

I imagine that the insulating properties of Neoprene wrapped around the coolant pipes that run below the tank would help reduce the heat transfer from the pipes to the tank.

You don't have to imagine, you can look it up. As an insulator, you want a low value for thermal conductivity.

neoprene*: 0.19W/mK

polyurethane foam of the type used to insulate household hot water pipes: About 0.02 W/mK

So about 10x better

And just for giggles, the conductivity air in the cavity without modification** is 0.03-0.04 W/mK

So in fact adding neoprene around your pipes would likely increase heat conduction to the tank over the air gap that's present originally..

*Wetsuits are made from neoprene foam, a value for the conductivity of which I can't find from a quick google search.

** This ignores convection which will improve this conductivity, but trying to model it gets very complex very fast. The point of a foam insulator is to trap air in a way that prevents convection currents.

[Chris_Von_Bron]

Great info Martin, thanks.
As the fuel tank plate hides the coolant pipes near the tank a household based material as mentioned would hopefully not perish as it wouldn’t be attacked by the elements. Is the tank held in place by the plate, I.e. when the plate is removed, will the tank fall or is it secured beyond being wedged in foam pads?

[FABombjoy]

polyurethane foam of the type used to insulate household hot water pipes: About 0.02 W/mK
In my experience this material works very well, even in the engine compartment (if kept away from direct exhaust heat). I used it in a few selective spots to loom and acoustically insulate, and on my AC hose & turbo water return hose as a "long-term temporary" anti-chafing measure.

One thing that adding a heat shield seemed to help with was my original steering rack. Before I had it rebuilt the steering would get sloppy as the car warmed up. I installed a very thick piece of polyurethane foam pipe insulation (probably 8cm outer diameter) on the rack body and onset of sloppiness was delayed. Usually enough to not be noticeable on shorter drives.

[DCUK Martin]

Great info Martin, thanks.
As the fuel tank plate hides the coolant pipes near the tank a household based material as mentioned would hopefully not perish as it wouldn’t be attacked by the elements.

http://lmgtfy.com/?q=polyurethane+chemical+resistance



Is the tank held in place by the plate, I.e. when the plate is removed, will the tank fall or is it secured beyond being wedged in foam pads?

The tank is pretty tightly wedged and can't come out until the coolant pipes are removed. I've never not needed to pry it out from the pointy end.

[David T]

Great info Martin, thanks.
As the fuel tank plate hides the coolant pipes near the tank a household based material as mentioned would hopefully not perish as it wouldn’t be attacked by the elements. Is the tank held in place by the plate, I.e. when the plate is removed, will the tank fall or is it secured beyond being wedged in foam pads?

As long as the tank is not full and has never been removed, it should stay in place if you remove the bottom cover. DO NOT ATTEMPT TO DRIVE WITHOUT THE COVER UNDER ANY CIRCUMSTANCES! One owner did and the tank fell out even though it seemed very tightly wedged in. Ruined the tank. There is no need to remove the tank unless you need to make repairs to the frame or the epoxy is badly peeling because you have brake fluid leaking all over and you want to repaint the frame. When the tank was installed they greased up the foam pads to make it easier to install. The grease hardened and acts like glue after 30 + years making it difficult to remove the tank.

[DMCMW Dave]

http://lmgtfy.com/?q=polyurethane+chemical+resistance

The tank is pretty tightly wedged and can't come out until the coolant pipes are removed. I've never not needed to pry it out from the pointy end.

Yeah - the tank is hard to get out when you want to get it out. Also to answer Chris' question - the tank area is exposed to the elements - all water that runs off the windshield lands on the tank and comes out of the triangular vents shaped into the tank cover. You don't want to use open cell foam in that space as is it will just hold water in there all the time and you will end up with corrosion issues.

[DCUK Martin]

You don't want to use open cell foam in that space as is it will just hold water in there all the time and you will end up with corrosion issues.

Pipe insulation is closed cell. If not sure, scrunch it up under water and see if it acts like a sponge or just wants to float.

[Chris_Von_Bron]

As long as the tank is not full and has never been removed, it should stay in place if you remove the bottom cover. DO NOT ATTEMPT TO DRIVE WITHOUT THE COVER UNDER ANY CIRCUMSTANCES! One owner did and the tank fell out even though it seemed very tightly wedged in. Ruined the tank. There is no need to remove the tank unless you need to make repairs to the frame or the epoxy is badly peeling because you have brake fluid leaking all over and you want to repaint the frame. When the tank was installed they greased up the foam pads to make it easier to install. The grease hardened and acts like glue after 30 + years making it difficult to remove the tank.

What kind of numpty would try driving the car with the panel removed :jawdrop:

My question was to know if I needed to provide support as the panel is removed so that gravity didn’t win. I’d like to remove my cover, add some pipe insulation and as per Martin’s valid point, if it doesn’t hold water then it shouldn’t create a problem for the chassis. I’ll make sure the tank is empty and will provide support during the fitting of pipe insulation as the tank has been removed already recently for other reasons.

I’ll also change the fuel pickup filter too as it looks fine but may be past its best.