41 replies to this topic

[rozzer1275]

ah right yer mine kept cracking on the heat effected zone of the weld on the y pipe, took me a couple of years and a few broken y pipes to figure if out i even welded them braced the y with bars and destressed the weld with heat, still no good. 3into1 no probs but there are no welds on the pipes.

[icklemini]

the welds seem to be fine... but the tubework just collapses.. like a bog toll tube.. can crush it in you hands...

[rozzer1275]

dam, thats some heat

[fatmini]

Quote " the welds seem to be fine... but the tubework just collapses.. like a bog toll tube.. can crush it in you hands... " Quote


thats exactly what happend to mine and it cracked on the welds ,then set my engine bay on fire !! lol

ive got some grate pics ill post up later

Edited by fatmini, 06 January 2009 - 11:09 PM.

[icklemini]

dam, thats some heat

aye - not just on one car, or one 'batch' of manifold... a regular thing...

[rozzer1275]

yer pics

[ash]

Quote " the welds seem to be fine... but the tubework just collapses.. like a bog toll tube.. can crush it in you hands... " Quote


thats exactly what happend to mine and it cracked on the welds ,then set my engine bay on fire !! lol

ive got some grate pics ill post up later

Wow scary! Show us some pics!

I have a Maniflow LCB so for now I think I'll try the heat shield idea. I have some stuff that plumbers use when welding to protect whatever's behind the pipes, so I'll fashion something out of that.

[fatmini]

some pics

Attached Files

•  manifold6.jpg   43.02K   22 downloads
•  manifold5.jpg   34.03K   10 downloads
•  manifold4.jpg   44.9K   14 downloads
•  manifold3.jpg   20.41K   10 downloads
•  manifold.jpg   24.9K   9 downloads

[fishy]

Something from my distant past tells me that this decay may be by a mechanism called "hydrogen embrittlement", this would explain the bog roll effect. I don't think there is anything that will stop this happening on a wrapped exhaust system other than a change of material (to a super alloy probably).

I expect it occurs at a slower rate on unwrapped manifolds, so the only real cure is to ceramic coat the manifolds to provide both insulation, and protection. If this is the case, then it makes for a pretty poor case in favour of using thermotec type wrap on anything other than a racing car, and even then the medium term cost analysis will probably favour the coating process.

Hope this helps

Paul

[fatmini]

This was the result after 9 months and 2000 miles of a well tuned and set up engine by peter Baldwin i.e. it wasn’t running lean at any stage of its life on the engine

Would the ceramic be applied to internal and external diameters?

Also I remember a time when stainless steel manifolds where sold the mild steel one is favoured because it isn’t as brittle and is more forgiving of the forward and backwards movement of most a series engines

Can you still by SS manifolds and if so does any one know who uses them and what the life expectancy of them are/is

[Dan]

From some photos we had posted on here a while ago, stainless manifolds don't last anywhere near as long as mild ones when wrapped. The warping is much more pronounced and happens really fast. I wrapped my first freeflow (mild steel) years ago and it also warped pretty quickly and developed pinholes. I had the wrap on for less than 6 months before I gave up on it. Another side effect I noticed was that becasue the heat is released further down the system, the interior of the car and in particular the whole tunnel becomes very, very hot. The rubber block mounting was actually starting to melt and without carpets the front section of the tunnel was too hot to touch at times. The engine was in proper tune, not lean and still there was tremendous heat. I'll never fit this stuff again. I'll make custom heat shields for areas that need it from flexible two-ply heat barrier. I do use the Thermotec clips for my CV gaiters though!

The main reason for wanting it is to keep the heat away from the feed from petrol pump to carb

That section of pipe should always be solid metal, preferably steel as original. You haven't replaced it with rubber have you?

Edited by Dan, 07 January 2009 - 10:37 PM.

[998dave]

Hmm some mixed views there. I'm a little bit worried about it 'corroding' and 'distorting' my manifold. The main reason for wanting it is to keep the heat away from the feed from petrol pump to carb and also because I thought it was good for performance to keep the heat it.

Did you consider moving the fuel pipe, you can rotate the pump outlet, then take the pipe almost straight up, onto the bulkhead, accross behind the carb, and into the carb?

Dave

[rozzer1275]

some pics

yep thats what i had, exactly the same. Cracked at heat effected zone of the weld.

also just read what dan said on mine the sound insulation has melted round the exhaust tunnel by the gear stick.

Edited by rozzer1275, 07 January 2009 - 11:06 PM.

[fatmini]

yeah didnt think the stainless would be much better if not worse .mine melted through the floor as its fiberglass !! lol 400degree plus heat mat bonded directly to the fiberglass did the trick tho

[Strontium Dog]

For what it's worth I use a ceramic coated mild steel downpipe on my 3sgte engine. It's 2ltr turbo at around 300bhp and so pushes some hot gasses out. The ceramic pipe looks near perfect 18 months and 10,000miles down the road! I'd say it radiates a bit more heat than a well lagged pipe but is still very effective.

If you choose to lag a steel pipe then you can give the lagging a liberal coating of high temp paint and that helps to prevent the lagging taking up any water. It also insulates the pipe even more I would have thought. Personally the only lagging I have used is on my fmic pipes post cooler where they run through the bay! Again not my Mini which boasts no lagging but does have a heat shield between the carb and the soot pipe.

My fuel pipe is also routed as per Dave's post using high quality fuel line!

Edited by Strontium Dog, 08 January 2009 - 12:10 AM.