Exhaust manifolds

PostPost by: billwill » Thu Nov 24, 2011 1:09 pm

pharriso wrote:
BobS2 wrote:Thought... doesn't everyone end up with a large collection of bits which are not in use but are too good to chuck away because "they might come in useful one day" ?

Cheers, Bob


Absolutely.... I have piles of half used Brake pads, distributor caps etc. My wife is giving me therapy to throw away such stuff....



My theory is that all tidy households with no clutter ultimately depend on us bits&pieces hoarders to fix their problems.

(and we should probably charge accordingly 8) ... 50% extra to any one who is a non-hoarder.)
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PostPost by: archigator » Thu Nov 24, 2011 3:25 pm

I thought I'd throw this one out their while everyone on this side of the pond is having their second helping of turkey this Thanksgiving and watching the Chasing Classic Cars marathon on the Velocity channel...

I took my headers to a highly recommended welding shop here in town; he does a lot of classic car work, and has been doing it for over 30 years. I had a leak in my stock (but Jet-Hot ceramic-coated) headers and took them to him for repair. He repaired the obvious crack, but after water-testing them, there was still a pinhole-sized leak where the back pipes join. He kept them overnight to effect a repair, and when I come by to pick them up this morning (yes, Thanksgiving) I find that he has added a lot of additional welding beyond the stock connection points.

I am concerned about differential heating in the headers and the potential for the weld to seperate as a result... he assures me this won't happen. He also says that there is still a minor leak that he couldn't access that might only be accessible with a toothpick and some JB weld or some epoxy product. Not feeling 100% about the job, since it still had a pinhole leak, he refused to take a dime for his work! (Guys like this are hard to find.)

My questions:
1. Are these welds going to hold? 2. Will JB Weld work for a pinhole leak? 3. Should I just break down and buy a new set of headers, because these will fail me in the near future?

Thanks.

Gary
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PostPost by: 69S4 » Thu Nov 24, 2011 4:04 pm

Definitely 3. Don't even think about putting them back on the car and buy a new set. I'll take the old ones off your hands and risk life and limb testing them to destruction on my car! :lol: :lol: :lol:

Presumably your concern about differential heating is whether the (now) uncoated and welded areas will expand faster than the areas that remain coated enough to crack the welds. I'd be amazed if it made the slightest difference personally but that only comes from a few scribbled guesses about expansion rates and seat of the pants experience. I've happily patched up a fair number of exhausts and manifolds over the years and not found it an issue. Re JB Weld type epoxies, I though somewhere around 200C was their limit but it's not as if you need structural strength to block a pinhole.
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PostPost by: Baggy2 » Thu Nov 24, 2011 4:34 pm

FWIW my guess is that unless the walls of the manifold tubing has got very thin the welds will hold but they are not very pretty! The JB 'weld' will not hold - I agree with the previous poster that epoxy falls apart around 200C (or lower?) and your maifold will get hotter than that - This side of the pond we have ' Gun Gum' . It really is a bodgers material but it will survive the temperature if you want to use it.
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PostPost by: StressCraxx » Thu Nov 24, 2011 7:57 pm

I have a repaired set like that on my Formula Ford, done about 5 years ago, only the welds are much uglier. No problems since. Put them back in and drive it.
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PostPost by: GrUmPyBoDgEr » Thu Nov 24, 2011 11:23 pm

Well if we're voting on it, I'm seconding your doubts Gary.
That manifold will crack (sooner or later) because:-
1. the sudden change in cross sectional area where all of that weld material is. Thermal stress.
2. the stiffness of the structure has been altered, putting higher localised bending stresses into the effectively shortened pipes.

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PostPost by: S2Jay » Fri Nov 25, 2011 2:38 am

elj221c, Roy: I used to work for Gale Banks Eng. & also for Borla for a time & I know of no one who uses stainless for the flange. It would be fabulously expensive to use a piece of S/S 1/4? thick or more [Banks uses 1/2? thick for their RV headers, Borla flanges usually range from 3/8? to 1/2? thick], so do not feel too badly toward whomever made the set you referred to ? it is common industry practice, at least in the U.S.

Next, not mentioned here, but perhaps just for common interest, is the difference in types of S/S. Borla built their reputation and launched the industry by using ?genuine? T304 Stainless. This is what most of us would expect to get if we ordered a ?stainless? manifold. Banks came later to the Pickup & RV market and discovered that ?T409? Stainless is much cheaper than T304 and yet it is defined as ?Stainless? b/c it has the minimum amount of chromium to meet that definition. Type 409 will have at least 10.5 to 11.75% chromium, 10% being the threshold for a Stainless Steel. T-304 will have 18 to 20 % Chromium and 8 to 12% nickel, where T409 may have 0 to< 1% Nickel.

The 409 will discolor a bit brownish over time, but it does not really rust as mild steel would in similar conditions. One quick test is to put a magnet up to the metal. As an austenitic stainless, T304 is non-magnetic, where the ferritic stainless T409 will attract the magnet.

Welding stainless can be a problem and may crack at the weld unless done properly. My experience has been that stainless wire or rod must be used, and then if the larger area, or entire piece, is annealed by heating and being allowed to cool, it should maintain integrity.

Archigator

As to the pinhole leak, yes it may not be a problem, but it may indicate that the condition of the metal on the unseen side is deteriorating. It would be helpful to know just what material was used in the construction. If it actually is a 300 series Stainless, then it is not likely to have an internal corrosion problem.

And I would buy your welder a TG pie, or maybe a gift card to Marie Cs!

Just my 2c.

Jay, 26 / 5009 [titled 1966 in Cal]
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PostPost by: StressCraxx » Fri Nov 25, 2011 3:21 am

S2Jay wrote:elj221c, Roy: I used to work for Gale Banks Eng. & also for Borla for a time & I know of no one who uses stainless for the flange. It would be fabulously expensive to use a piece of S/S 1/4? thick or more [Banks uses 1/2? thick for their RV headers, Borla flanges usually range from 3/8? to 1/2? thick], so do not feel too badly toward whomever made the set you referred to ? it is common industry practice, at least in the U.S.

Next, not mentioned here, but perhaps just for common interest, is the difference in types of S/S. Borla built their reputation and launched the industry by using ?genuine? T304 Stainless. This is what most of us would expect to get if we ordered a ?stainless? manifold. Banks came later to the Pickup & RV market and discovered that ?T409? Stainless is much cheaper than T304 and yet it is defined as ?Stainless? b/c it has the minimum amount of chromium to meet that definition. Type 409 will have at least 10.5 to 11.75% chromium, 10% being the threshold for a Stainless Steel. T-304 will have 18 to 20 % Chromium and 8 to 12% nickel, where T409 may have 0 to< 1% Nickel.

The 409 will discolor a bit brownish over time, but it does not really rust as mild steel would in similar conditions. One quick test is to put a magnet up to the metal. As an austenitic stainless, T304 is non-magnetic, where the ferritic stainless T409 will attract the magnet.

Welding stainless can be a problem and may crack at the weld unless done properly. My experience has been that stainless wire or rod must be used, and then if the larger area, or entire piece, is annealed by heating and being allowed to cool, it should maintain integrity.

Archigator

As to the pinhole leak, yes it may not be a problem, but it may indicate that the condition of the metal on the unseen side is deteriorating. It would be helpful to know just what material was used in the construction. If it actually is a 300 series Stainless, then it is not likely to have an internal corrosion problem.

And I would buy your welder a TG pie, or maybe a gift card to Marie Cs!

Just my 2c.

Jay, 26 / 5009 [titled 1966 in Cal]
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Jay,

Agree about the different grades of stainless. The earliest headers were nickel plated mild steel. If that is one of the Dave Bean SS headers, it is W304 A213 tube. They are built by Barry Callouette here in Benicia. Low carbon content is important to prevent cracking and so annealing is not required after welding. Of course, taking the car out on the highway for a couple of hours brings the headers up to annealing temperature. 304 turns a straw color anyway unless they are ceramic coated.

Welding on used, worn out headers is challenging work.

The high end ss race headers are made with T321 or 347 stainless to keep the carbon in solution to prevent cracking. If money is no object some teams use Ti.
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PostPost by: archigator » Fri Nov 25, 2011 2:49 pm

Jay,

Just to set the record straight, I took my welder a large pacakge of pastries and tarts from a nearby French bakery this morning (as was always my intention.) They were well received. :D

We don't want the local car restoration shops thinking that Lotus owners are pikers!

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PostPost by: elj221c » Sun Nov 27, 2011 1:12 pm

S2Jay wrote:elj221c, Roy: I used to work for Gale Banks Eng. & also for Borla for a time & I know of no one who uses stainless for the flange. It would be fabulously expensive to use a piece of S/S 1/4? thick or more [Banks uses 1/2? thick for their RV headers, Borla flanges usually range from 3/8? to 1/2? thick], so do not feel too badly toward whomever made the set you referred to ? it is common industry practice, at least in the U.S.


Jay, thanks for that.

I will just clean the flanges up and reuse them. It will save me the cost of replacement. :)
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PostPost by: S2Jay » Wed Nov 30, 2011 5:57 pm

Archigator:

Gary,

Glad to see the follow up on your welder guy story, but I want to add that I did not intend anything personal with my comment, it was just a throwaway line that sounded amusing when I wrote it, not considering any personal impact. :oops:

I figured there was more to your story, but sometimes it is too much detail to write, or we forget that others may want to know more than we really need to. It is great to encourage guys like that who want to do the right thing. :)

Jay
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PostPost by: elanner » Sat Dec 24, 2011 2:17 pm

Two exhaust questions:

1/ In replacing my exhaust system I have realized that the downpipes from the exhaust manifolds/headers do not bend sufficiently under the bell housing to align with the gearbox exhaust bracket clamp. They are angled a few degrees downwards. The Y piece that I have is straight and, by the time it has been fitted to the end of the downpipes, it is almost impossible to fit the intermediate pipe and then bend it so that it can be clamped to the rear of the gearbox. And ground clearance is compromised. My exhaust/muffler guy did finally manage to fit the intermediate pipe - see picture. It works but it?s a bit of a mess, especially around the gearbox clamp, which, although it doesn?t show in the picture, had to be severely distorted. (Ignore the remnants of the plastic shopping bag that has cleverly welded itself to the pipe!)

Two solutions to fix the problem properly seem to be:
- Remove the manifolds and bend the ends a bit more (the asking-for-trouble approach).
- Acquire a Y piece with a bend in it, so that its output pipe aligns with the gearbox bracket clamp.

Could somebody let me know if a Y piece with a bend in it is obtainable? The usual suspects don?t have them. I think I?ve seen them in the past.

I guess another approach would be to modify the straight Y piece. The two legs wouldn?t fit in a pipe bender, but perhaps it would be possible to cut little wedges out of them, and then bend and weld them.

2/ Due to the first problem the previous exhaust system did not include the bracket that is clamped to the rear of the gearbox. On fitting a bracket I realised that the lower bolt needs to be oil tight. Mine isn?t. The current fitting order is gearbox -> bracket -> spring-washer -> bolt. Needless to say, oil leaks around the spring washer and possibly from between the gearbox and the bracket. It was probably leaking slightly before fitting the bracket, but adding it has made the leak worse.

Rather than resorting to trial and error can somebody recommend a fitting order that won?t leak?

Elan_Y-piece.jpeg and


On the bright side, removing the stainless steel system that was on the car and fitting a mild steel system has definitely improved the sound. It?s not only quieter, it?s also much more satisfying/pleasant. Noticeably less harsh/boomy and annoying. (I managed to snag what Susan Miller told me was her last twin box mild steel S4 silencer - whoo hoo!)

Gee, I'm not qualified to disparage stainless systems, I?m sure there are good ones out there. I?ve no idea where mine came from - it was a Sprint one acquired in the UK some years ago by the previous owner. But it sounded wrong from the very moment he started the car when I was buying it.

Nick
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PostPost by: Elanman99 » Sat Dec 24, 2011 4:38 pm

Nick

I sympathise with your dilemma on your exhaust pipe problem. This is the sort of thing that prompted me to create the 'Plea to the makers of Elan parts' topic recently.

The original Lotus steel exhaust manifolds and 'Y' piece were never precision made but at least they were made to a jig or template that was accurate enough to represent a real engine and chassis. In the 70s I fitted several sets of these manifolds (bought over the counter from a Lotus dealer) and every one fitted easily but more importantly left the 'Y' piece outlet pointing in the right direction. When the set on my car eventually rusted through I replaced it with an after market manifold that I carefully tarted up and had enamelled before trying to fit them to the car. I had an almighty struggle! the two pipes are about the right distance apart to suit the 'Y' but they are not parallel to each other and one points downwards more than the other.

I don't know what the process is when a parts supplier commissions a company to supply them with a product. I can only speculate that an exhaust system manufacturer might be given a rusty clapped out set of manifolds and then being asked to make '20 sets to this design'. There is every possibility that the sample set themselves were not Lotus originals so its not surprising that many owners find themselves in the situation you are in now.

The Elan exhaust system originally was a snug fit, it ran close to, and parallel to, the underside of chassis and ground clearance was never an issue.

I think all you can do now is try and adapt what you have by cutting and welding.

Ian Phillips
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PostPost by: oldelanman » Sat Dec 24, 2011 4:58 pm

Hi Nick,
It can be a struggle to get all the bits to line up nicely - even if they are all correctly made and your problem may in part be due to the way that the system has been installed. The manifolds will tend to droop under their own weight due to the clearance on the bolt holes in the flange so if not supported while bolting up they will end up pointing downwards a bit. I would try undoing all the clamps, including the one on the muffler and slacken off the manifold nuts. Make sure all the pipe joints are free to rotate and slide in and out then align the system as it should be and support it while you tighten all the clamps and manifold nuts. I remember having to do this on my system to get it all to line up nicely otherwise gravity takes over.
Exhaust (7).jpg and



Regarding the oil leak - did you re-apply sealer to the threads of the bolts you removed to fit the exhaust support bracket? Also there is a gasket between the gearbox and the extension housing and it could be leaking from there.

Regards,
Roger
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PostPost by: elj221c » Sun Dec 25, 2011 12:18 pm

elanner wrote:On the bright side, removing the stainless steel system that was on the car and fitting a mild steel system has definitely improved the sound. It?s not only quieter, it?s also much more satisfying/pleasant. Noticeably less harsh/boomy and annoying.

Nick, I seem to remember that there were issues at a Lotus track day a couple of years ago with cars fitted with SS systems failing the drive past noise test.
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