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Brian Vogel
Grand Master
Username: guyslp

Post Number: 317
Registered: 6-2009
Posted on Sunday, 31 March, 2013 - 11:55 am:   Edit PostDelete PostView Post/Check IP

Hello All,

Now that the whole fan bit is done with LRK37110 it's time to start planning out the next sequence of repairs.

She's now starting very easily and running very well when the choke's on, and slightly rough when the choke goes off. I noticed that the temperature of the carbs (both cold) was somewhat different today after running the car about 15 minuted but I also noticed that the one above the left side of the engine is in a location that's got a distinctly warmer "updraft" than the one on the right side.

The exhaust pipes are still like swiss cheese and the exhaust fumes are still quite pungent and can cause eye irritation even with the garage door open.

Just as a note, the carbs had a full R&R in November 2004, at 23,061 miles, several years before she went "into hibernation." Right now the mileage is 26,537. I don't know whether any of this is significant, but more background can't hurt.

I don't know whether it's sensible to start dealing with the carbs while the exhaust system lacks the necessary impermeability or whether I should try to tweak them first in hopes of getting rid of the asphyxiation causing exhaust fumes.

Advice appreciated.

Brian
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Richard Treacy
Grand Master
Username: richard_treacy

Post Number: 2805
Registered: 4-2003
Posted on Sunday, 31 March, 2013 - 07:20 pm:   Edit PostDelete PostView Post/Check IP

You probably simply need to set the mixture with the engine hot after a 15 minute drive. It sounds like it's running rich. Adjusting the mixture is a scheduled yearly maintenance requirement with a carburettor-equipped SY.

As time goes on, carburettors normally wear to give rise to a richer mixture This is not an issue with fuel injected cars as they are maintenance free to the point of having tamper-proof plugs fitted to the mixture control systems.

RT.
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Benoit Leus
Frequent User
Username: benoitleus

Post Number: 52
Registered: 6-2009
Posted on Sunday, 31 March, 2013 - 07:24 pm:   Edit PostDelete PostView Post/Check IP

Hi Brian,
I struggled with the same problem for ages. I changed everything possible but still it ran a little bit rough. A "specialized" mechanic adjusted the carbs to no avail. In the end I took it to a small local garage who again adjusted the carbs and since then it ran smoothly again. Worth a try.

Benoit
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Richard Treacy
Grand Master
Username: richard_treacy

Post Number: 2806
Registered: 4-2003
Posted on Sunday, 31 March, 2013 - 08:56 pm:   Edit PostDelete PostView Post/Check IP

As an aside, I'm puzzled about the holey exhaust. Only the downpipes and the crosspipe are of mild steel on this type of SY, and they run hot enough to last for a century. The rest of the system, pipes mufflers and all, is stainless and should last forever apart from possible damage or metal fatigue.

RT.
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Brian Vogel
Grand Master
Username: guyslp

Post Number: 319
Registered: 6-2009
Posted on Monday, 01 April, 2013 - 12:20 am:   Edit PostDelete PostView Post/Check IP

Richard,

I can assure you, for whatever reason, that the pipes between the various catalytic converters, mufflers, etc., on this car are definitely mild steel. Even when stainless "goes bad" from heat, and it does (or it does when it's used to make LP burners), it doesn't rust the way these pipes have.

It's clear that one of the pipes once encountered some solid object with sufficient force to put a long, inverted 'V' shaped dent in it and it has rusted through following the apex. The others, I believe, have suffered from "lets run the car for a few minutes" syndrome where all the condensed water simply sat in the bottom of the pipes and eventually rusted them out. I'll have to get some "before" photos at some point.

I guess I should definitely seek out a stainless system when I take the car to have that work done. I found it odd that the cats & mufflers are all completely intact as far as I can tell. There's nothing in the maintenance records that I have (which are incomplete) that state anything about exhaust system work.

I suppose I should take my copy of SU Carburetters: Tuning Tips & Techniques along with me on my upcoming road trip and presume that I should do the carb adjustment first.

Brian
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Geoff Wootton
Prolific User
Username: dounraey

Post Number: 143
Registered: 5-2012
Posted on Monday, 01 April, 2013 - 02:53 am:   Edit PostDelete PostView Post/Check IP

Hi Brian,

It's the same on the SY1, the interconnecting pipes between the stainless steel boxes are mild steel. The reason I was given was RR engineers used them to damp down the tinny sound they were getting from an all stainless steel system. I have no way of checking the veracity of that statement, it's just what I read earlier. In any case, it seems to defeat the object of using stainless steel at all. On my car all of the holes were where the mild steel pipes were welded to the stainless boxes. The increased back pressure produced by replacing the rear part of my system has revealed a slight blow on the front silencer box, so that is up for replacement shortly.

For the carbs, I found the Edelbrock unisyn carbalancer at $26 to be really very useful. Just remove the two U shaped air inlet pipes and hold it over the carburettor air intakes. It's a great way of checking the balance of the two carbs. I also use a Gunson's colortune. This is a love/hate device; some people hate them, others find them invaluable. I find the gunson very useful for finding a good starting point for setting the mixture strength once I have balanced the carburretors.

Two possible sources of air leaks into the intake manifold are

1. The pipe that runs down to the gearbox modulator.

2. The pipes that run to the speedostat cruise control. Note that an air leak can be introduced from the solenoid plunger not seating properly inside the speedstat unit.
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David Gore
Moderator
Username: david_gore

Post Number: 1257
Registered: 4-2003
Posted on Monday, 01 April, 2013 - 10:18 am:   Edit PostDelete PostView Post/Check IP

Stainless steel welded to mild steel and the presence of moisture - an ideal galvanic cell for corrosion. While the pipe gets hot when in use, it can also get and remain wet when cold or there is sufficient water dripping from the underside of the car after use to cool the pipe to stop evaporation and the evaporation residues left behind often contain corrosive compounds so accelerated corrosion of the mild steel adjacent to the weld is inevitable. Welding with unstabilised or non low-carbon filler materials will increase the susceptibility of the weld itself to corrosion. The mild steel will also dilute the alloy content of the weld if high-alloy filler is not used during welding thus further reducing its corrosion resistance.

For these reasons, it is imperative the exhaust headers and balance pipe should be stainless steel to match the rest of the system to minimise this problem.

The noise problem with stainless steel exhaust systems compared to mild steel systems is simply due to economic factors; to keep the cost of the system down, a light-gauge metal tube is used which is inherently less effective than heavy gauge metal tube in attenuating sound. A stainless steel system made from the same gauge metal tube as a mild steel system will have the same level of noise attenuation - we came up against this problem many years ago in Australia when developing stainless steel after-market replacement exhaust systems [also the "spring-back" problem when bending austenitic stainless steel tube which I referred to in a recent post about restoring bent wheel trims].

In reference to Brian's observation about stainless steel "going bad" when used for burners [or other high-temperature applications], the scaling resistance of stainless steel and other heat-resisting materials is a direct function of the alloy content [which determines the scaling temperature], flue gas composition and temperature. The most appropriate material requires knowledge of the operating conditions involved and many alloys will not be suitable. The widely available commercial stainless steel alloys start to scale at temperatures above 800deg Celsius [a cherry-red colour when viewed in low-light environments] although this can decrease in some environments. Most flames have a higher temperature than 800deg C - a candle flame can easily reach 1000deg C although its heating capacity is restricted by its size.

David - who spent his working life cursing the person who called Iron-Chromium-Nickel alloys "stainless steel" instead of their proper description of "corrosion and heat-resisting" steels. If Stainless Steel was truly stainless, how did the "Ad Astra" stainless steel sculpture outside the Smithsonian Institute Air and Space Museum in Washington D.C. get its gold colour?

http://en.wikipedia.org/wiki/Ad_Astra_%28Lippold_sculpture%29

Answer: Australian ingenuity and lateral thinking from a small company located in the Sydney suburb of St Peters.
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Brian Vogel
Grand Master
Username: guyslp

Post Number: 321
Registered: 6-2009
Posted on Monday, 01 April, 2013 - 01:01 pm:   Edit PostDelete PostView Post/Check IP

Mr. Gore,

So, is the answer to your rhetorical question the addition of some specific trace metal to the stainless alloy?

I'd imagine that most metal alloys can be tinted through "better living through metallurgy." Heaven knows one can make gold show a myriad of colors depending on the alloy.

Brian, not asking for trade secrets (and who's definitely not a metallurgist)
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Richard Treacy
Grand Master
Username: richard_treacy

Post Number: 2807
Registered: 4-2003
Posted on Monday, 01 April, 2013 - 02:15 pm:   Edit PostDelete PostView Post/Check IP

Perhaps should update TSD5681 in the Technical Library (it is a special section included in the SY spare parts manual and referenced from the title page of that manual) along with the contemporary magazine reports. Then perhaps not. They all state that the exhaust system went stainless, apart from the downpipes and front crosspipe, for the Silver Shadow II (ie 30,000-series SYs). Sure, the earlier cars have mild steel pipes with stainless silencers although most, like my T-Series, will have been replaced by fully-stainless systems by now. Most likely the vehicle in question has had a budget replacement system fitted at some stage as such systems are offered out of the box by aftermarket Crewe specialists. Although the stainless systems do not corrode, they can suffer damage or silencer failures. The sound deadening material inside the stainless boxes does have a limited life.

RT.
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David Gore
Moderator
Username: david_gore

Post Number: 1258
Registered: 4-2003
Posted on Monday, 01 April, 2013 - 03:01 pm:   Edit PostDelete PostView Post/Check IP

Brian, nothing as simple as your premise unfortunately. The Chromium and Nickel contents dictate stainless steel will have an inherent silver colour which cannot be substantially altered by alloying.

In the early 1970's, International Nickel [Inco] developed and patented a variation on the traditional electroplating process which allowed a translucent film of varying thickness to be produced on the surface of stainless steel which appeared coloured due to thin-film light interference [just like the colours produced when you put a drop of oil on still water and allow it to spread in sunlight]. The technology worked very well but colour consistency between batches was another thing altogether and this was the problem faced by the Australian licensee when colouring the sections used to create "Ad Astra".

After much experimentation involving Inco and Comsteel technical staff and the licensee, a way of producing an acceptable colour was found and the sculpture was successfully fabricated and installed in Washington.

Coloured stainless steel is still being made by a variety of techniques depending on the desired finished appearance and the technology has improved way beyond what I saw in the mid-1970's.
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Vladimir Ivanovich Kirillov
Experienced User
Username: soviet

Post Number: 31
Registered: 2-2013
Posted on Tuesday, 02 April, 2013 - 06:49 am:   Edit PostDelete PostView Post/Check IP

Defineately fix the exhaust leak before you get carbon monoxide poisoning fiddling with the carbys while its running. Its not a fun gas to inhale although some say it a bit like getting stoned if you don't die. I recall in the owners manual there is a technique for storing RR. Old fuel residue left in the carbys can play pranks later on. My experience is that old fuel can also play pranks with fuel injection big time because the injectors get sticky and believe me injectors do wear and when they wear the mixture goes extremely rich because instead of atomizing the fuel they hose the fuel in or dribble it madly. A carby, especially an SU is not going to wear out by sitting.It only wears out over a very long time whilst in use. My experience with fuel cleaners on carbys and injectors is that its like snake oil - works for some but never worked for me. Stale fuel is a death sentence to spark plugs. If you are not a mechanic, get yourself an exhaust gas analysiser. An old one in good condition especially if its made in USA or UK would be better than a Chinese one. Also get a carby synchroniser. With these two specialised tools it won't be hard for you to get the carbys perfect again if it is them in the first place. My experience is that a lot of people tear down a carby and make it worse by introducing dirt etc into the fuel system. Be certain that your carbys are at fault before going the full fiddle.
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Randy Roberson
Prolific User
Username: wascator

Post Number: 111
Registered: 5-2009
Posted on Tuesday, 02 April, 2013 - 10:27 am:   Edit PostDelete PostView Post/Check IP

Seems to me that, apart from safety concerns which are certainly valid, the exhaust leaks can damage the underbody and possibly the carpeting and associated trimmings. In any case it is certainly undignified to proceed with one's exhaust out of control.
With good brakes and a nicely-sorted engine and transmission, I vote for the exhaust. It will also be a long-lived upgrade.
Randy, who has no skin in the game, only an opinion.
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Brian Vogel
Grand Master
Username: guyslp

Post Number: 322
Registered: 6-2009
Posted on Tuesday, 02 April, 2013 - 11:35 am:   Edit PostDelete PostView Post/Check IP

Randy & Vladimir,

Thanks for the input. Just FYI, the car is still not in the "ready for roadtime" stage and I never run the car except with the garage door open. If I did I'd already be dead, or at least have eyes that water for months.

My main reason for asking is that I wondered if leaky exhaust could have some impact on how the carbs would be tuned or, perhaps, be thrown out of tune once the exhaust is repaired. If that's not a concern I'll probably work on the carbs next for cash flow reasons.

Brian
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Geoff Wootton
Prolific User
Username: dounraey

Post Number: 147
Registered: 5-2012
Posted on Tuesday, 02 April, 2013 - 01:00 pm:   Edit PostDelete PostView Post/Check IP

Hi Brian

It's difficult to predict whether a new exhaust system will require re-tuning of the carbs. Your current exhaust, with holes in it, will mean less back-pressure which is a good thing, but it will also have less of a scavenging effect on the exhaust gases, which is a bad thing. Exhausts are a compromise between these two competing factors. Replacing the exhaust will mean the balance of these two factors will change, however they may compensate each other out, meaning you do not have to re-tune them. It's impossible to tell.

Since it is so easy to tune the carbs, why not tune them anyway and then again when you have replaced the exhaust.
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Randy Roberson
Prolific User
Username: wascator

Post Number: 112
Registered: 5-2009
Posted on Tuesday, 02 April, 2013 - 11:03 pm:   Edit PostDelete PostView Post/Check IP

Agree with Geoff; the only other effice I have seen is if there is an oxygen sensor involved: exhaust leaks upstream of the sensor can actually entrain air thereby bringing oxygen into contact with the sensor and throwing off the sensor reading. This will result in the engine running much too rich.
The pungency of the exhaust fumes is rarely encountered anymore, except for us hobbyists. Richness seems to make them worse, too. I think you will be fine as long as the exhaust leak is not overheating anything underneath.

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