Exhaust header/manifold

[Simon TR4a]

I have been using a header for the last several years and have noticed it allows a lot of heat near the carbs and has also caused the insulation on the generator wires to get cracked. Finally, unlike a V8 header which has a large metal flange to which the tubes are welded, because the intake ports are on the same side of the head the ports don't line up well with the header tubes.
I have one of the rare 4a factory cast manifolds 4-2-1 style, which looks as if it would flow pretty well, and I am thinking of getting it coated and using it.
An old Road and Track article shows a moderate gain on a Spitfire from changing to a header, and my engine has other mods which I don't want to waste by bottling up the exhaust; has anyone seen or done any tests of the factory manifold against headers on a moderately tuned engine?
Opinions welcome, facts even more welcome!
Simon.

 

[vettedog72]

Simon:
There are insulating wraps that reduce the heat loss from the headers, keeping the heat inside and increasing the efficiency of the header. If you ask me for dyno’s, I have never seen one showing the before and after, much less any dyno’s specifically for a TR4. On the other hand I have seen and benefited from the insulating wrap keeping other surrounding header apparatuses from being effected by the heat. I know this does not address the miss alignment of the header and port; if a little grinding will not make things align up, it sounds like a significant defect. Who made the header?

 

[gjh2007]

Simon:

Check out Jegs.com for header wrap, they have all the high perf. stuff for american muscle, but heat, is heat!

 

[Stinky]

I heard some where that there is some sort of coating(I think it's a Ceramic Coating) that can be applied to headers, or any other exhaust pipe for that matter that greatly reduces the heat radiating from the pipe/header.
Surely someone here know's more about this coating?

 

[Simon TR4a]

Thanks for the quick responses guys; the header was ordered through Moss, and to be fair it may have got bent in shipping, but it is much too strong for me to bend back.
I think the only way would be to cut the tube and reweld the flange.
i had considered the wrap but it has a reputation for rusting the headers if it gets wet from rain or washing the car. I could coat the header then insulate the generator wires I suppose.
I have done some port matching by grinding the port, but don't want to go too far in case I change back to the manifold or a header that fits better. Again I suppose it could be built up with JB Weld or similar, but the more I think about it the more I'm inclined to go back to the factory manifold; just seems like less trouble, even if it costs a couple of bhp!
Simon.

 

[Alan_Myers]

Hi Simon,

The stock TR4A manifold is said to be pretty good flowing and certainly is an option. The two tube design is said to be the most efficient of all the Triumph 4-cylinder designs and better than many OEM exh. manifolds on other makes of cars. But, I don't have any scientific information to support that.

A header is likely to produce a little better, and is pretty much mandatory for use on engines tuned for high rpm performance on the race track. If you were wanting to get every last ounce of power out of the car, with a hot cam, big valves, etc. etc., a header is the only way to go. I'd also recommend a header for any car running Weber side draft carbs.

But, for street cars with a stock to moderately improved engine, that OEM manifold would likely do fine.

I do have a mild steel header on my TR4, installed 25 years ago. It was originally a bit of a project to fit and took some tweaking. That's not uncommon. It was originally chromed and now has a nice patina of surface rust over most of it.

Yes, a header does put more heat under the hood and it's close to the carbs, starter, generator and the brake pipes. I insulated the brake pipes and brake switch wiring (that wiring is probably not a prob on your car, since the brake switch is located differently) with special cloth tubing designed for that purpose and widely available.

On the other hand, the OEM manifold puts some heat under the hood, too. Only a little less than a header will.

In my case, I will be wrapping a new header (on backorder since January!) for more effective temp reductions under the hood of my car. But, the primary purpose for wrapping is really to keep gas temps high inside the header, helping create a more efficient flow.

In fact, with mild steel headers you can only cover 65-70% of the header with wrap. If it were completely wrapped, the internal temps would quickly ruin the header. For that reason, I'm changing to stainless steel which can be wrapped 100%.

Wrap comes in black or white, in 1" and 2" widths and in various length rolls. It should take about 50 feet of 2" to totally cover a TR4/4A header. If you decide to install it, try soaking it in water for a little while to make it easier to install. Special high temp resistant clamps are needed to fasten it in a few key places, too.

There are also available high temp coatings that can be sprayed onto the wrap to help protect it against the elements, you can buy these in typical spray cans. One can is usually sufficient for a 4-cylinder header.

However, even with the sealing coating on it, wrap still will not last forever and needs replacement every so often. It does allow intrusion of water that will be most harmful on cars that are only occasionally driven. Daily drivers will "dry out" the wrap better. In fact, for the same reason, daily drivers are usually fine equipped with a mild steel exhaust systems, while cars that are used only occasionally actually benefit more from a stainless steel system.

Be aware that wrapping a header will void any manufacturer's warranty, but it sounds like the one you have is older anyway, so that may not be an issue.

You also mentioned ceramic coating, and that's a good alternative. It's a great way to clean up an old header that's still sound and usable, or one that's been repaired. It also helps reduce underhood temps, but probably not as much as 100% wrapping would on a stainless header. Ceramic coating would be my choice for mild steel headers.

Ceramic coating coats both the inside and the outside of the header. It also helps promote more efficient gas flow. It's a bit more permanent than wrapping, but will also void any manufacturer's warranties on a newly purchased header.

Most headers avail. for TRs are pretty much as you describe, unless you spend a lot more on something like a Stahl or have a header custom made. The Stahl is probably the top of the line that's still in production for TR2/3/4s, but is only available in uncoated, mild steel and costs about the same or more than a stainless steel header.

Before giving up on the header you've got, I'd suggest having a professional shop look at it and see if they can help match it better to the ports. This would best be done before having any coating or wrapping done, since it may involve some welding and grinding (the one on my TR4 did, when it was first installed).

I don't recommend modifying the head to match the header. Instead modify the header to match the head.

There are also "performance" manifold gaskets, just a little thicker material, that might help mounting and matching the header.

If you aren't sure if your header is mild or stainless steel, a simple test is a magnet. It will attract to mild steel, but not to stainless.

Cheers!

Alan

 

[vagt6]

I checked on "Jet Hot" ceramic coating for a GT6 header, it costs about $180 plus shipping.

I heard lots of good comments on the Jet Hot process but have no firsthand experience.

I found it by a "Google" search.

good luck, let us know.

 

[Guest]

Simon,
I installed the Falcon stainless (6-3-2, two-piece) header on my TR6. I had the original cast manifold on which I had Jet Hot coated. The cast manifold holds heat for a very long time. In fact, I had shot (with a laser-guided heat sensing gun) the manifold while running, shortly after shutting down and 30 minutes later. The darn thing emits a lot of heat! Thirty minutes after shutdown, it was almost as hot as while running. I forgot the figures but it was over 400 degrees I believe. The stainless header under the same testing showed similar results, it just cooled down a lot faster. Could touch it half hour after shutdown. So, it seems to me that the header emits a similar amount of heat, but dissipates it much faster. I find it difficult to believe that the addition of headers would cause damaging heat problems to surrounding parts, unless the header, being more bulky, tends to be closer to surrounding parts (starter, etc.) There was no room to wrap my header at all. Most of the pipes were virtually touching each other. The 4-banger would probably have a little more room to work. I did wrap my starter and am in the process of designing a heat shield to deflect heat from the triple manifold above it, although there really isn't that much heat in this area (again, the heat sensor gun). Jet Hot does a wonderful job of coating and have a very quick turnaround time. In fact, the factory twin cast manifold I removed (Jet Hot coated) is for sale if anyone is interested. I did have to slightly grind the flange on the header for fit, but the machined mating surface fit perfect. I am told that most mild steel headers are poor in fit (and quality) and usually need to be machined before using. That was not the case with the Falcons. Too, I used the thicker gasket for a perfect seal.

Bill

 

[prb51]

I've used header wrap with good results. In the case of two pipes being too close together you wrap the two as one. Rust problems only arise if the wrap is soaked and the car not run, or run very little. The benefits are a much cooler air space for the carbs and intake air. You can usually touch the pipes a min or so after shutdown with out a problem ( good if you need a roadside carb adjust). I put them on to keep from getting carb fuel starvation in our Az summer heat (100+ and idling) and it worked very well. Carbs a float bowls appreciably cooler. I couldn't 'feel' an improvement in performance but that wasn't my motive. You will smell the wrap when hot for a week or so as it 'sets' and then that goes away. I'd use it again.