Heat shield question

[kmack]

Ok, so here one for ya'll to think about...

I have the stock heat shield from a '73 over my header (6-2) and I'm pretty sure I'm still getting a heat problem in my carbs when running down the highway. These "warm" Texas summers aren't helping matters. So I'm looking to modify my heat shield to combat the heat coming off the headers.

I have an opportunity to get ahold of some asbestos fabric and was thinking about using this and apllying it to the heat shield. I figure pop-rivets would work better than glue (not sure I could find a glue capable of handling the heat).

Now I know all about the precautions regarding asbestos. I've been involved in the removal aspect of it. What I'm curious about is if it will help keep my carbs and fuel lines a little cooler. I'm going to be using my car for racing (in the hot Texas sun) so I'll need something anyway, just wanting to know your views on this.

Any and all comments welcome...

[Ed]

What year carbs are you using? And are you running water through your intake manifold?

I also have a 73 but I'm using 71 carbs with the 71 heat shield over my 6-1 headers. I haven't had any problems running in 100+ weather.

What kind of problems are you experiencing?

[2ManyZs]

I don't think I would use asbestos, you might run into problems with the EPA!

Seriously though, I think you could find better products on the parket than asbestos. Try looking at the Pegasus web-site, they have some heat shield material that is not too expensive you could try. Only other thing is buying a header blanket. Not the tape, you can get a blanket that slips over the header that would work much better IMO. I used the tape on the old IT car and didn't like it. If you run in rain it will absorb moisture and cause the header to rust out that much faster.

I would recommend the blanket for this reason, the heat needs to stay in the header as much as possible. If you allow it to escape into the engine compartment it heats up the whole compartment, so no amount of shielding under the intake is going to do any good once the underhood temp goes up. You need to keep it in the exhaust system where it will escape the engine compartment to keep the underhood temps to a reasonable degree. With the blanket you not only help keep the exhaust heat inside the header, but the radiant heat from the header will be kept mainly inside the blanket. I believe Pegasus also has these and perhaps MSA, can't remember where I got mine, it's one of those things that has never been out of the box yet. I can't say for sutre it will work better than header tape, but the idea is sound at least.

Only other thing is to route outside air from the grill area, the open hole on the side of the radiator support is a good place to put some type of ducting to route cooler air to the intake/exhaust area. Or perhaps an electric pusher fan in front of the radiator to force more air through the radiator and keep the air circulating under the hood when you are driving at slower speeds.

[skip260z]

http://www.heatshieldproducts.com/products.htm

[kmack]

"What year carbs are you using? And are you running water through your intake manifold?

What kind of problems are you experiencing?"

I have '71 carbs, on a '73 intake w/ '73 heat shield. What I'm experiencing is a slight studder or hestitation under acceleration at speed. I noticed that if I tried to touch the fuel rail, I couldn't. It was way too hot. I am running water through the intake.

"I think you could find better products on the parket than asbestos."

Well, the asbestos is free. I can't get much cheaper than that. But you bring up a good point about the overall under hood temps. I'll have to take a look at that. Maybe I'll look at wrapping the fuel bowls also. Just an idea.

My main concern is that the fuel is boiling in the rail and/or the fuel bowls.

[Ed]

Kmack,

I've got the same set-up in my 73. And I don't have any problems running in 100+ weather with the A/C running.

Correct me if I am wrong guys but slight studder or hesitation under acceleration might be an Ignition or timing problem.

I have heard that using a header blanket "traps" the heat around the header making it extreamly hot and causing the header to warp. Might be just a rumor.

[SFMRZ]

Asbestos = Cancer

There are still many lawsuits in the courts and it has been determined that asbestos causes cancer in the lungs.

I would not even come near the stuff even if it was for free, long life is price less.

[Doehring]

Why don't you feed your carbs another way?

I led a fuel rail/hoses from the pump to the left outside front (in front of the radiator), along that front in fresh air and back to the engine compartment at the right side and feeding the carbs from there. I also built in a much bigger heat shield by using 2 aluminium plates and a sandwich composition (also made from aluminium ) in between. Nothing is glued, it's all riveted or screwed. I also enlarged and added loles at the left front besides the radiator to get more fresh air to the carbs when driving. At the moment I think about an additional "hot air escape" at the left side underneath the windshield washing water bowl. I could also use the 280 Z hood, but that doesn't look original for a '72 240 Z.

By the way, I use 3 double SK carbs.

Rolf

[Doehring]

Sorry friends,

I mixed left and right. I'm getting old but still 7 years to retirement.

Rolf

[Leeroy]

Keep the heat in the exhaust!! Keeping the headers and upper exhaust hot is good because hotter air escapes faster and allows for more flow SO more power!! Having not used header tape I couldn't give an opinion, but I've heard fantastic things about it..also if you do want to use it there is some spray on paint that the same company provides to waterseal the tape and preserve it so that it lasts longer! Otherwise, the wrap works great (I also suggest that over the top of the wrap you bolt in a heatshield [thin piece of metal, at least 5mm away from the wrap] that directs the heat coming from the headers down and under the car...you can't reduce the heat the header makes, but you can choose where you wan't to put it, and not under your bonnet!!).

Also, your header won't warp unless its heated enough to nearly melt it, or if after a fast run (whilst its still hot) you decide to throw icy water over it (hot + cold = bending/warping).

'Thermotec' heat management products are available pretty much anywhere, and are all good quality...so unless you're only into a particular product, I highly recommend that you try them!!

Cheers!!:classic:

PS Sorry about the long message, but I couldn't make it any shorter!!