Lagging a new Bell manifold?

[Duncan Goose]

I'm just about to fit a new Bell manifold and TSSC supplied sports exhaust to my 1967 GT6.  Apparently not lagging the manifold can cause overheating and the carbs to 'boil'.  Thoughts?

[Pete Lewis]

with an engine driven fan that wont happen 

wrapping can degrade the pipework rapidly you dont want that .

i ran my Vit 6 for years she would go like the wind and idle for an hour without missing a beat 

do you have temperature compensators on the side of your carbs  thers go out of spec and the needles set too rich to compensate then when hot the car fumbles into a stall

these need to be fully shut by tighening the small nut inside and set the need;e  with the delrin washer level with the base of the air piston and the mixture is now near correct 

and heat wont be a problem ..       the idea that not wrapping gives problems is misguided and its other settings that give the problems 

keep a cold air intake to the filters no silly pancakes and it will be fine 

the 6-3-1 joint is the biggest problem they can be very leaky    nobody tells you that !!!

there are fixes to modify a leaker 

Pete

[johny]

Also they can be wrapped in-situ (although a bit fiddly) so you can always do that at a later date if theres a problem...

[Nigel Clark]

I've had a Bell manifold on my GT6 for about 20 years. It's never been lagged but I have fitted alloy carb heat shields.

The car has never had a problem with carbs overheating, either in 2 litre format with Stromberg CDSE 150s, or more recently 2.5 litre with twin SU HS6s.

Nigel

[DJB350Z]

I have to ask. What is a bell manifold?

[trigolf]

Made by Bell exhaust systems

[Pete Lewis]

he is nicks solution to the leaky slip joint on the 631 collector  we copied the idea welded some nuts and drilled theout out to add a clamp bolt and nut  

sealers do not work as the pipes expansion is always on the shuffle  , clamping may invite pipe fracures later on but the silence is worth it 

all tubular are noisey  ( you hear all the detonation pings ) no body tells you that but if the joint leaks it can be awful

Pete

[Dick Twitchen]

Like Nigel I have never had the problem you are worried about in my 1967 GT6 with an unlagged 6-3-1, and that is over about 15 years of year round use home and abroad.  Heat shields fitted.

Dick  

[DerekS]

It's all personal choice and depends on what you want from your pride and joy. I had a tubular manifold and pancakes on, they had been professionally fitted for the first owner, however there were problems. The main one was the heat in the cabin at foot level, on a warm day especially, was a horrible experience. This combined with the racket and the effects of drawing hot air into the carbs was not for me. Taking it back to factory spec made it far more civilised to drive. As I say though, depends on what you want. 

Derek.

P.s. memories of going out on a cold day, me turning the heater off because my feet were melting and 'er indoors complaining that her feet were freezing...

[Colin Lindsay]

1 minute ago, DerekS said:

P.s. memories of going out on a cold day, me turning the heater off because my feet were melting and 'er indoors complaining that her feet were freezing...

I remember last summer in the Herald convertible, me with a t-shirt on talking about how warm it was and 'er with two coats on, a hat, a scarf, a blanket over her and still freezing.

However no such problems in the GT6, always warm inside but never needed to lag the Phoenix exhaust I had fitted.

[NonMember]

20 minutes ago, DerekS said:

P.s. memories of going out on a cold day, me turning the heater off because my feet were melting and 'er indoors complaining that her feet were freezing...

I used to get that in the GT6. It's less noticeable now that I've fitted a decent gearbox cover - my feet are now a little on the cool side.

[JohnD]

22 hours ago, Duncan Goose said:

I'm just about to fit a new Bell manifold and TSSC supplied sports exhaust to my 1967 GT6.  Apparently not lagging the manifold can cause overheating and the carbs to 'boil'.  Thoughts?

Duncan,

The Internal Combustion Engine is an extraordinarily inefficient!    Only in the last decade, just as it is about to be phased out in favour of EVs, have engines been developed that can turn 50% of the fuel energy into motion.   'Our' engines are less than  40%  efficient, and the energy wasted comes out as noise, vibration and  HEAT!     That's why you have a great  big radiator on the front of it, that dumps all that heat in to the engine compartment.      The heat that comes from the exhaust manifold is tiny in comparison to the radiator output, and 'lagging' the manifold will have zero effect on under bonnet temperature. There may be some direct radiative heat transfer from the manifold to other components nearby like the carbs, but the best solution for that is a heat shield -lots of posts about those are available.

 

Then, 'lagging' can have a bad effect on the manifold itself.    I speak from experience!    I wrapped mine in glass-fibre tape, which  eventually became so tatty looking that I took it off.    The manifold underneath had corroded, not by ordinary rust but by large flakes that broke off as I removed the tape.   The flakes were solid but brittle, and I think were the result of low oxygen under the wrap, with high heat causing the steel to  change into "ferrous" oxide, a black compound rather than the red "ferric" oxide that we usually see.

Lastly, wrapping can make no difference!     The Space Shuttle was made of aluminium, and re-entry into atmosphere would heat the wings and nose above the softening point of metal, so it was covered with insulating tiles.     The temperature difference between the outside and inside of the Shuttle had to be much the same as the temperature inside the manifold in relation to normal air temperature, about 800C.      To acheiove this, the Shuttle needed tiles up to 150mm thick.     How can a wrap of glass fibre tape at most 2mm thick be effective at keeping the heat in?

Don't bother with  wrapping!    But get a heat shield for the  carburettors.

John

[NonMember]

58 minutes ago, JohnD said:

The temperature difference between the outside and inside of the Shuttle had to be much the same as the temperature inside the manifold in relation to normal air temperature, about 800C. 

I believe your figures are mistaken, John. The temperature of the aluminium frame needs to be kept down to about 150C but the forward surfaces reach nearly 1650C during re-entry. By my reckoning that makes the temperature difference almost double what you quote.

(Not that it makes all that much difference to the point about a thin wrap of tape)

[JohnD]

Thank you, Non-member, but as you say, a detail that leaves the argument valid.