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It was two and half-years ago I ordered the SS manifolds, Time flies and I was shocked now that many new, cast iron manifolds that were selling about GBP225 a piece are no longer available. There are quite a few listings for new manifolds (can't remember, just front or the rear) selling for over GBP300 and US$400. Such money could deter many who are planning to give up their cars when they become uneconomically viable to run or keep. So naturally, there is a good demand for used manifolds, but the asking prices of these increasingly difficult to find used manifolds have also gone up quite a bit, and some have hairline cracks (still a crack!) whereas others might develop cracks soon after.
Rose still has the original, cracked, welded (but still cracked) factory manifolds on, pending a gradual recovery process. Some time down the road, I have to tackle the manifolds. However, having now carefully seen the manifolds in the original shipping box, I sought further advice from the UK shop on their original thoughts on its application, as apparently my original intention to keep the secondary air pump (air injection) and ERG features was not taken on board. Although it has now been confirmed that Rose does not have ERG, alas, I have two new ERG valves and will have no use of them.
Anyway. as new, factory original or OEM manifolds are no longer available, and the SS manifolds in an as-is situation, I will have no choice but to make do with them. The advice I got from the UK workshop is that the SS manifolds were deliberately given a longer travel before turning downwards (for better flow and lessen the crack factor), so the heat shield has to be removed, and any metal wiring (air injection inlets and pipes) would have to be relocated (or removed altogether). This will require modification to the original length of the dual downpipes, which each has a re-cat and an O2 sensor some inches down the pipe, as the equal length 2 x 3 manifold pipes and their bends being moved farther away from the engine block would mean a merging point past the "collector" that is lower than the original connecting level between the original manifolds and downpipes. The only solution is to cut away the pre-cats from the downpipes and let two short extension pipes from the collectors connect to the downpipes that are now shorter without the pre-cats. I was told that many X300 in the UK have had their pre-cats removed and this would not affect the O2 sensors or trigger the engine light. I have seen comments in this and other forums that this is common practice, and in some regions where there is no emission control, some even have the floor cats removed. I won't go as far as other folks (in any case there is pretty stern emission control here in Hong Kong) and will keep the floor cats and maybe re-position the O2 sensors beyond the floor cat so they still get some real-time emission reading, better still if I can still feed the ECU with separate data of the two banks.
By design, the SS manifolds are just tacked together to allow careful re-positioning by trial and error before full welding. This will be quite a challenge to the local shop here. It is always much better to have the manifolds and adjustments done with the car present. Wish me luck.....
Just so you know, I am running no cat's with both set's of 02 sensors connected and it definitely triggers the CEL. I'm in the US and my car was originally configured as a California car for emissions purposes. I have the OEM Jaguar downpipes with no cat's installed, so the O2 sensors are in the original position
The X300's are unique, in that the O2 sensors are after the first catalyst on the downpipe. North American cars and those with greater emissions systems will have 4 O2 sensors, and the upstream ones are the check. It's the reverse of just about every other car on the road. So I would not move the O2 sensors to after the floor catalyst, but if you only have 2 to begin with they should work fine. if you have 4 that's a different matter.
There are four cats and only two O2 sensors on my XJR. The O2 sensors supply live data to the engine ECU to regulate the fuel mixture, while the cats all do one thing, to filter harmful gas in the exhaust, for the environment but more importantly to comply with legal requirements. With this premise, one other option for me is to retain the O2 sensors in the original positions on the downpipes, but simply cut away the cats from the upper position. Bearing in mind that the car originally also has air injection to dilute the exhaust before reaching the O2 sensors, I just wonder how doing away with the pre-cats and the air injection feature might affect the combustion mixture and engine performance. Yes, I know that some X300 in other markets have different configurations regarding emission control, but I imagine that the ECU would have corresponding match to handle the variations.
Here is an update. Took the stainless steel headers to an exhaust specialist shop for installation last week. There were a few surprises: the alignment of the exhaust manifold was not in perfect leveling; the angle of the bends was slightly over, hence touching the engine block; the two "cups" that held the three equal-length pipes together were too long, hence surpassing the landing platform of the factory downpipes; and two of the equal-length pipes were too close together and hence obstructing the head screws on the engine block. The whole set of stainless steel manifolds and assembly had to be taken apart and welded back together by trial and error. To allow sufficient clearance for the steering column, the upper conical part of the downpipes, which is in fact the top part of the front cat, had to be cut out and a pair of flanges newly made on the shortened downpipes to hook up with the downward extension from the manifolds. Furthermore, the original heat shield has to be removed to make way for the manifolds that extends farther away from the engine block. The EGR valve and air-injection pump had to be taken out as their pipes would be in the way.
It took the exhaust workshop two full days to make the modifications and tests for fitment. Test drove the car for three days and found air leak at the flanges between the manifolds and the downpipes, and between the Y pipe and the floor pipe. Took it back to the workshop and the problems were quickly fixed.
My mechanic said the removal of the factory heat shield might expose the air-conditioning pipes and power steering hose to heat from the manifolds. Hence he custom-made a heat shield using antimony alloy to divert the heat emanating from the headers.
The engine is much quieter now that the cracked factory manifolds have been replaced by the stainless steel headers, and with the front cats retained, the engine check light did not emerge. However, CO level seems a bit high, ranging from 3.5% to 4% during idling; the legal tolerance is 0.5%. I have new O2 sensors but have not yet replaced the front cats and floor cats. Idling once reaching operational temperature ranged between 900 rpm and 1250 rpm, and can momentarily go up to 1300 or 1400 rpm. So these irregularities have yet to be addressed.
+1 for the thanks on the update. I also inquired about these from the same supplier as OP. The supplier did say that what they are supplying is basicly DIY kit and will most likely need adjustment in situ as they did not have suitable x300 car available for perfecting the fit.
On side note I randomly stumbled to a local fabricator who mainly is working with american muscle cars that had made headers also for x300 xjr so I think if needed i go that direction instead.
Who is your supplier?
i don't think you would be judged as promoting the supplier by telling us.
it sounds like the U.K. guys with the double-barrelled company name that I have temporarily forgotten. I have considered getting the kit too, but need to find a local SS exhaust guy willing to take it on. Also , I have bought Andys exhaust diameter and length plans so don't want to buy a kit that differs..
Hayward and Scott is the UK company that made the ops headers
https://www.haywardandscott.com
and like said they were very upfront with stating that it is more of a DIY kit than finished product when i was talking to them. Also they were giving option of customising the primary pipe diameter (two different options IIRC).
the local guy is indie fabricator that does everything from drag car chassis fabrication to small parts
Yes, the stainless steel manifolds for my XJR were indeed made by Hayward & Scott (H&S) in the UK. My advice is, if possible, get the manifolds done at a local workshop that will be able to take measurements from your car AND install the manifolds for you. There was too much guess work as in my instance I had to ask H&S to find an X300 in its neigbourhood to take some initial measurements, and then tack the half-finished pipes loosely together (see picture)
so when they arrived in Hong Kong I could ask a local workshop to modify the lot for a good fit. As explained in post #5 above, considerable modifications were needed. My original intention was to retain the ERG valve and air-injection features and H&S even bought the ERG inlet sockets but things got convoluted when drawing up the specifications by a long trail of email exchanges. The manifold assembly arrived two years ago but the attention of the time was Rose falling into coma so the whole carton box was left untouched, only opened lately and moved around with Rose when looking for a willing and capable workshop to wake her up first. The result was that I only found from the now opened box that some parts were missing. However. the long delay and the car and box having visited many workshops and places did not justify holding H&S responsible. In a recent communication, H&S explained that its all-time intention was to remove the front cats so the joining pipes can connect without clearance problem with the Y joint.... I also found that the stainless steel manifolds turned yellow quickly after a short journey. The local workshop said this indicates that it was made of 304 grade steel, and a magnet quickly confirms that this is so. In all fairness, H&S never stated that the manifolds would be made of 304 grade stainless steel. The manifold assembly cost GBP800, and shipment by DHL set me back by another GBP140.
The cost of modifications to make the lot fit on my XJR locally was about GBP600, so all things considered, it would both save time and money as well as ensure a tight fit by custom-making the manifolds locally. However, this has never been a viable option in Hong Kong as there isn't any really good workshop that has the expertise to make the manifolds.
Sorry, an important word found missing from my post #10 above.
"......The local workshop said this indicates that it was NOT made of 304 grade steel, and a magnet quickly confirms that this is so. In all fairness, H&S never stated..... ". In conducting a magnet test, the workshop showed that the magnet quickly attached to the H&S manifolds. The workshop said this meant that the manifolds were made of mild steel at best. I had a pair of stainless steel tail boxes (not yet installed) in the boot at the time - the magnet had no response when sliding round both boxes. However, no matter what, the stainless steel manifolds will outlast the car.
Sorry, an important word found missing from my post #10 above.
"......The local workshop said this indicates that it was NOT made of 304 grade steel, and a magnet quickly confirms that this is so. In all fairness, H&S never stated..... ". In conducting a magnet test, the workshop showed that the magnet quickly attached to the H&S manifolds. The workshop said this meant that the manifolds were made of mild steel at best. I had a pair of stainless steel tail boxes (not yet installed) in the boot at the time - the magnet had no response when sliding round both boxes. However, no matter what, the stainless steel manifolds will outlast the car.
"The most popular stainless steel is Type 304, which contains approximately 18 percent chromium and 8 percent nickel. At room temperature, the thermodynamically stable crystal structure of 304 stainless steel is bcc; nevertheless, the alloy's nickel concentration, as well as the small amounts of manganese (about 1 percent), carbon (less than 0.08 percent) and nitrogen (about 0.06 percent), maintains an fcc structure and therefore the alloy is nonmagnetic. If the alloy is mechanically deformed, i.e. bent, at room temperature, it will partially transform to the ferritic phase and will be partly magnetic, or ferromagnetic, as it is more precisely termed."
Maybe some additional testing will reveal if the headers are SS or not. If they were mild steel, if nothing else I'd think they would rust easily if you left some water on them? H&S could likely confirm too.
Yes, I agree that the magnet test may not be conclusive, but the magnet did respond differently to H&S' exhaust manifolds and the uninstalled stainless steel tail boxes. The latter was bought from eBay off a reputable exhaust specialist manufacturer in the US clearly stating that the tail boxes are made of 304 grade stainless steel. Also, as per the prediction of the local workshop, the H&S exhaust manifolds did turn yellowish within the first two hours of normal driving. I tumbled over H&S in the first place to enquire about a set of stainless steel exhaust manifolds for XJ6 featured on its site, but was told it was meant for 1976ish versions of the XJ6. I later asked about the possibility of H&S custom-making the exhaust manifolds in stainless steel for X300, and volunteered to be the guinea pig for X300's stainless steel exhaust manifolds, on the understanding that other forum members were watching and might eventually be interested in group orders to lower costs. In quoting me the price of GBP800, H&S advised that the exhaust manifolds would be "hand made out of good quality stainless steel". Maybe only I mistakenly expected that 304 grade steel would be used. I realize that neither was 304 mentioned in H&S' XJ6 exhaust manifolds listing. However, I am happy now that the manifolds do they job well.
so, Qvhk, what performance benefit have you noticed?
I have Andy's exhaust dimension plans but still haven't got around to having a set made.
There is an exhaust guy here who can make from scratch in mild steel but not stainless, or I go the route you went - buy a kit from H&S and find a stainless welder to assemble. I want to be sure it is money well spent however..
Here is a picture of the H&S manifolds turning yellowish after a day's drive, taken when I removed the fabricated heat shield to fit heat resistant wrap to the AC pipe and nearby cables to reduce heat.
I cannot accurately judge the full difference between the original cast iron manifolds and the H&S manifolds, as the factory manifolds were leaking badly from multiple cracks, and I did not have a chance driving Rose before recovery from three years' coma. However, I can say Rose is very sure footed with the new manifolds, and with Andy's timing advance through the new ECU setting, she pulls like a mad bull, and self-restrain is my only advice to avoid being targeted by any law enforcement agents. The other day a Lamborghini was pushing hard from behind but was stunned seeing Rose breaking loose like a rocket - being a manual the 3rd gear is incredible in lightning acceleration.
On choosing between making a set of manifolds locally or ordering from H&S, I would advise going for local. As explained in Posts #1 and 5 of this thread, there are many challenges for H&S to custom-make the manifolds without your car present, and the resultant modification work would be immense and expensive (see my costs mentioned in my earlier posts). You also avoid shipping costs. I forgot to mention H&S' manifolds were made based on Andy's specifications on the diameters of the primary and secondary pipes and the length of the primary pipes. The length of the pipes downstream will be determined by the real car present during installation. In custom-making them, I had asked a forum buddy to send a set of used manifolds to H&S for measurements, authorized H&S to purchase EGR gasket EBC10827 on my behalf to determine the spacing for the studs and the size of the outlet hole, and suggest H&S to find an X300 in its neigbourhood to determine clearance measurements (they told me they found an XJR just across the street). These were just too long hand.....
After installing H&S manifolds, I have to return to the local exhaust workshop twice to fix air leaks:
(i) the first visit was to fix an air leak from the gasket (workshop material) between the downpipes and the cut joints of the 3x2 primary pipes, which was proven to be too thin, and another air leak between the Y joint assembly and the floor pipe due to strain from the installation angle (to make sufficient clearance for the longer primary pipes, the original downpipes was shortened with the upper part of the front cats removed);
(ii) the second visit was to fix a very small crack in the floor weld from the first fix.
So modifications for a good fit might take quite a while.
So you will be lucky if you can find a local shop that is willing to make AND install the manifolds for you. You will have the paramount advantage of being able to supervise the work and choose between whatever situations or options that may crop up during the way. Several wishes of mine were lost during the email exchanges (94 !!!) from start to finish, so you will certainly wish to avoid that.
One other option is for H&S just to copy the factory exhaust manifolds and make them in 304 stainless steel, so it would guarantee universal fit, and longer if not permanent life.
Last edited by Qvhk; 04-15-2017 at 11:03 PM.
Reason: adding a paragraph on post-installation leak fixes
And then a local exhaust guy could make a set of mild steel ones up. He won't do SS.
My ideal would be to get him to make me a set then get a jig made so we could turn them out for others. However that may be too much hassle and there may not be the demand.
I think there will be a demand for replacement manifolds even made of mild steel, but not in great numbers. The factory manifolds are all sold out and are unlikely available any more or available cheap. British Parts listed them between GBP140 and GBP180, but already out of stock; Jaguar Classic Parts and David Manners list the front manifold at GBP287..... so you can do your math. If British Parts replenish its stock, that would be the best solution as its manifolds are more affordable, and there is no point buying manifolds at prices that would outlast your X300. If not, then imagine having to buy a pair of factory originals at about GBP560 plus shipment, then a local solution even with mild steel would have some appeal.
My rear manifold is cracked and I can't see buying a new one that will eventually crack as well. What are the options beside OEM cast? Does welding them, assuming I can find a local shop that can weld cast, last over time? If I did headers I would want them in 304.
Welding will only extend the life of the manifold for a short while, as new cracks will develop along the welding places, no matter how well the workmanship is. I have a pair of factory original, cracked-welded-and-cracked-again manifolds with me so anyone can have them to copy and fabricate new ones using mild steel or 304. I believe making exact copies rather than playing with the rest of the set-up would be the best way to go. Whether you want to keep/remove the front cats or modify the floor pipes/silencers/taiboxes, etc. would be a downstream solution up to the individuals.
If the exhaust manifolds crack because it is a design flaw, which why else would mine and from what I have read others, have cracked at 73,000 miles? Jaguar/Ford should have made good on replacing them with a newer design.
Am I correct that a quality header, even if a non long tube design (shorty) isn't readily available off the shelf is because of the limited number of potential buyers? My goal would not be added performance but, added reliability.
02-27-2017, 12:34 AM
Exhaust Manifolds and Downpipes Modifications
