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Wrapping exhaust manifold


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When i first put my SS down pipes on I don’t have warp on and the pipes were very hot, so I installed some with the engine in the car but that was a bit tricky, but when I did the engine rebuild I wrapped the pipes before I put the engine in, much easier it does keep the heat in you can still work on this side of the engine if you have to and not burn your hand or arm.

 Mike Redrose group 

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On 9/16/2021 at 9:52 AM, john.r.davies said:

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I rest my case.

^ which case is that John ?  :rolleyes:

If it's in regard to neatness .. Rowlocks.   On a 1950's sports car I think Peter W's looks every bit the part.  And I should think in an under-bonnet photo, showing the engine bay with inner arches and bulkhead, then that insulation would not be detrimental to the overall impression, nor hardly be noticed insomuch as the exhaust down-pipes are barely seen under the inlet manifolds, carbs and linkages.  

And anyway, as Peter says. .

On 9/15/2021 at 5:51 PM, BlueTR3A-5EKT said:

It is wrapped in foil face asbestos strips from the aircraft world.

 We used fit a long sleeve of the stuff over pipe work near the turbine/jet pipe of turbine engines to stop those pipes cooking.   I merely cut the stitching, flattened the tube to a long sheet and wound it round the stainless manifold pipes, retaining with stainless locking wire.

ie., he's used wrapping that was made for the job ..and thought to be very worthwhile by the aircraft engineers, but not a proprietary product which may look prettier under a car's bonnet.  I've done a neat job by first tucking the end in, so there's no feather edges and then like other have used stainless steel ties which were neat.  As Mike says, it's very tricky (I think impossible) to do a really neat job with the engine / manifold in the car,  but quite possible ..to do neatly when the manifold / pipes are first removed.

Btw. anyone using this stuff is best advised to wear gloves. Its fibres are rather uncomfortable in the skin.  

Pete

 

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On 9/15/2021 at 10:26 AM, Bfg said:

..well there's some interesting answers to consider, and to be honest I'm surprised by the general bias against.

I don't have definitive answers, but I do plan to wrap my TR4A's manifolds, as indeed I have done so with previous classic cars.     

In answer to Graham’s original question, I use 2” because half of its width overlays the previous wrap, and down a pipe 2" tends to stay neater and needs less ties.  Around a cast manifold with lots of tight corners I might go for 1" wide. 

How long ? ..each wrap of 2" wide goes down the pipe 1” and the length of each wrap can be approximated as ;  pi x D (or to round things off  3 x outside diameter of the pipe).  If there are 4 pipes, each 15” long of 1 ½” diameter, then the maths is simply ; (3 x1½” per wrap) x 1 x 15” x 4 = 270” (7m).  You’ll have to check the outside diameter and lengths of your particular manifolds to determine a more accurate figure, but very likely 10m roll will sort you out.

 

What was the thinking behind wrapping ?  

Contrary to Dave’s summation, the hotter the gas - the lower its viscosity, which therefore it blasts through the exhaust faster.  A performance exhaust such as the 4 branch Phoenix is designed for faster engine speeds & high revs., so that’s fine.   More quickly moving the gasses out of such a pipe reduces back pressure and indeed its inertia (slight vacuum between each pulsation) tends to draws the exhaust from the combustion chamber more quickly.

It also has the benefit of hot gasses reaching the tail-pipe, which soon dries out condensation throughout the exhaust system and lessens sooting up. 

Other benefits include lessening under bonnet temperatures, because if the heat is coming out of the exhaust tail pipe then it cannot also be coming out in the under-bonnet space.  This offers benefits ;

·      less heat to be transmitted through the bulkhead and gearbox tunnel.  

·      If air into the carb is drawn from under-bonnet then it is better for that to be cooler / denser, and therefore more power is produced in combustion.

In addition to the convective heat of under-bonnet-temperatures is radiant heat, which is detrimental to ;

·      the wiring, any rubber (steering column joints for example) and plastic parts, and engine ancillaries (such as the dynamo and starter motor), as well as under bonnet paint and finishes exposed to that heat.

·      the engine block itself is very much less exposed to radiant heat from the manifolds. Whose water jacket is only a few inches away from those pipes.

These things are ever more pertinent when stuck in traffic.

·     manifolds being wrapped might also prevent your getting burnt, and/or some discomfort when working on the engine or when tuning.  

Ceramic coating is likely to be better, particularly on cast manifolds.  It lasts well and looks good.   My old Jaguar 3.8 (six cylinder) had ceramic coated cast-iron manifolds which was standard specification, No problems with those manifolds cracking from that heat.  It was a good job too because the PAS reservoir and pump were within inches of the forward branch, and the space between those manifolds and the straight-six slab-sided engine block was very tight.  

Another benefit, particularly with stainless steel pipes, is that wrapping adds a layer of sound insulation to soften what can otherwise a rather tinny sound from pipes (internal echoes I guess).  I have no experience of corrosion of the pipes, but then I do tend to avoid stainless down-pipes. 

Hope these thoughts help you balance the weight of opinion.

Pete

p.s.  have you asked the exhaust pipe manufacturers what they think about wrapping ? 

 

Thanks Pete. Lots of thoughts there to balance the ship. 

Graham 

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