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MG Midget and Sprite General - manifold heat wrap

Just finished wrapping manifold in heat wrap bandage as i was having problems with fuel evaporation,when stripping carbs off i found the rear float bowl was hanging off!!,luckily only needed tightening up. on comletion now seems a lot quieter,going to try out tomorrow,going to a classic show near by at Fiddlers Ferry near Warrington. Hand are now cut to ribbons now though!! HaHa
p kiely

Good luck when do you intend to replace the cracked exhaust manifold.......
Onno Könemann

Was gnna say the same as Onno

Mild steel manifold wont last long when wrapped, stainless will be a bit better, but a good heatshield will be the cheapest long term option
PeterJMoore

We have found bhp can suffer with the wrap as the heat tends to be held back in the head, we have also found this to be so with stainless manifolds and no heat wrap. We have seen a heat wrapped standard B cast iron ex manifold warp by 1/4" and never fit again after half a dozen races in a standard class!

As Onno and PK say....best have a physical barrier to keep heat away from inlet/carbs.

Peter
P Burgess

I agree with Peter having found similar results with racing Spridgets and Spitfires. I've seen wrapped tubular manifolds go half way through a race season.

Furthermore, heat wrapping will change the exhaust gas velocity so if you have a tuned manifold it will throw the calculations for Primary and Secondary pipe length/bore into kilter.
Deborah Evans

So what are your views on that ceramic exhaust paint, would that have the same effect ?
K Harris

I haven't tested ceramic coated stuff yet, if the coating is on the inside then maybe heat will just dissipate further down the system and not be kept in the header/manifold. If the coating is only to the outside then maybe the heat will be trapped as with heatwrap.

Ceramic seems to be getting popular so maybe we will find out on the rolling road soon.

Peter
P Burgess

My 1500 suffered a head gascket failure soon after fittinng heat wrap on the manifold. There seemed to be a lot of heat around the central ports with the studs affected badly. I remived the heat wrap and replaced the standard fan , fuel evaporation cured!!
C Bintcliffe

I wraped my previous exhaustmanifold and this is what happened: it cracked and started delaminating/peeling layers of metall off...
Had to get a new manifold... stainles steel and unwrapped this time.

It still amazes me that some people/cars get a way with it without troubles.


Arie de Best

Thanks for the info guys,got me worried now, car fitted with tubular manifold & stainless heat shield,What do you suggest best option, thinking maybe fix some heat blanket to rear of heat shield maybe & remove from manifold pipes,any suggestions??
p kiely

Well, since you identified a problem, then, why not give it a trial with that sorted, and, see what happens?!

When you say you're suffering from fuel evaporation - at what rate?
rachmacb

my question is are you suffering from fuel evaporation?!

what are the symptoms?
This does not happen easly.

What setup do you have engine carbs cooling ventilation etc.
Onno Könemann

Ok,Set up standard 1275 Twin Carbs,Problem has happened a few times,e.g. Recent trip to Midget50,drove from Cheshire to Corley,no probs,On run in to Stamford the crew stopped a few times on route, when re-starting from hot car hesitant to start,Happened again on recent visit to Tatton, drove there without any probs,on turning into car park car cut out and wouldnt restart had to push into parking area!!,once cooled down started normally & ran without any problems.

p kiely

Sorry - can I just confirm - it runs rough when hot?

When it's running - where does the temp gauge sit?
rachmacb

Also - lovely front end - any chance you've got a photo looking down at the carbs etc?!
rachmacb

So you have not checked for spark or fuel flow on the moment of trouble?!

Next time you have the problem first check if you have spark (lots of ignition parts are heat sensitive)

If you do then check if you have fuel.
Just unscrew the pipe on the carb and have a asistant turn on the ignition.
see if you have fuel and turn of the ignition and quickly push the hose back (relax it will not go up in flames if you want have a botle ready)

If you have both then you might have fuel evaporation.

I never had it with several "hot" engine's and several carb setups even on very hot days.
Not saying it can not happen just saying other things are more likely
Onno Könemann

No it doesnt run rough, when stopped after a run struggles to restart immediately,temp gauge sits normal temp & no overheating issues,however when i removed the carbs the rear float bowl was very loose,could this have been the problem? have tightened this up.
p kiely

Hot start problems associated with carbs must be very rare on a 1275 setup. Our highest failure rate ( non start when hot)in order is rotor arm (use a 'proper' red one), condenser (find old one or fit aftermarket special), poor power supply to coil(starter motor saps power and resulting voltage is low) engine catches when ignition key returned to run position while flywheel momentum keeps engine turning. Poor wiring harness, some of the looms are getting very long in the tooth.

Peter
P Burgess

Sounds more like a coil to me, the hot non starting rather than fuel.
K Harris

This thread was discussed between 09/07/2011 and 12/07/2011

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