Everybody says X300 exhaust manifolds are a pig to repair and pretty much all X300 manifolds are cracked by now.

I picked up a couple of cracked ones as spares and a very accomplished welder I know said he'd have a go at fixing them. Unfortunately, they both warped in the process. One popped the weld when it was bolted back on and the other blows a gale around the gasket.

I could get someone to plane a few mm off them, but there's still that cracked weld to fix.

The old ones are cracked but they're now better than these two so they'll go back on and we'll have to hope it passes the MOT.

Of course, Jaguar still sell new ones. £210 each.

 

In the distant past I repaired a couple of exhaust manifolds by brazing, but they had to be either bolted in place or to a heavy plate.

 

Someone or some supplier needs to start make stainless headers for our cars.

 

I'm surprised someone in England didn't start doing so years ago.

 

I actually make the headers from a expert design direct fit 304 stainless steel but they are not cheap

I spent close to 10 grand developing and prototyping them

If you would like more info just private message me

I to got sick of repairing the headers I spent 3 grand on repairs and replacements before I made the full system for my car

No problems for 2 years and 40,000 k,s couldn't say that about repaired or replacement ones they lasted an average of 9 moths each time

 

Ooh they're pretty!

 

we need a video posted to hear how they sounds, as well as, more details of the rest of your exhaust systems

 

Headers alone don't make a sound difference they might if they where paper thin but the one,s I make are 304 stainless steel the sound they actually make is quiet no sound at all (LOL)

Its the exhaust that makes the sound my headers are a direct replacement fit to the single underfloor pipe they have the O2 sensor bungs but have no front cats as they are tuned length and having cats at the front will not make them tuned length

I have tried to video the system last time I had the car dynoed but the sound just distorts very badly so is useless

I will do another dyno run just as soon as I figure out why the throttle is sticking

I have attached some pix of my car with its system

A bit of overkill but I don't plan on selling my car ever

I have basically rebuilt it since 2008 so its not worth selling
I am planning to put it into storage as I believe the XJR cars might be collectable one day as they only made the S/C AJ 16 engine for 2 years before going to an 8 cylinder engine

I did learn a lot doing this exercise I.E. I used a 2.1/2 inch pipe split after the single 3 inch out of the headers
I should have gone for twin 2 inch and instead of 2 catalytic converters with 2/1/2 inch diameters I should have used a single 3 inch catalytic converter and instead of twin 2.1/2 inch resonators I should have used a 3 inch inlet to twin 2 inch outlet like this muffler Dynomax® Performance Exhaust | Mufflers | Dynomax VT™ Muffler

My logic was that being supercharged it would need to breathe well twin 2/1/2 inch is to much the drone is unbearable that's why I have 3 mufflers under my car to quieten down the droning

When I did my car no one had done a full system on one of these cars so it was an experiment that's why it cost so much for my system knowing what I know now I would have done it differently single Cat single VT dynomax resonator and twin mufflers at the rear large diameter engine pipe after headers then twin 2 inch pipes for the rear mufflers

I could have used of the shelf products instead of all hand made and designed a significant cost saving

All knowledge I am happy to share
I searched for years for headers before I finally bit the bullet and did my system I was sick of cracked headers and the associated cost of repairing them also when the cast headers crack the car sounds like a piece of crap embarrassing when you are at the lights

 

Very nice. I assume the ECU is happy with the removal of the front cats and I requires no changes?

 

I guess it doesn't care if the cats are missing, as long as the O2 sensors are there. That's a beautiful system....

 

front exhaust manifolds, guess who has two in PERFECT order

 

Just to add - I called AJ6 engineering earlier. They use to fabricate and sell headers but didn't sell many so gave it up.

 

Sorta depends :-)

Remember that USA and some other market X300s have four oxygen sensors, pre- and post- converter. These cars would certainly "know" if the cat wasn't there. You'd get get a CEL and (I reckon) P0420 and P0430 codes or some other fault indication.

X300s with just two oxygen sensors are a different kettle of fish.

Cheers
DD

 

With and more manifolds cracking the demand might now be high enough to justify production again?

Cheers
DD

 

The reason I made them was AJ6 Engineering stopped making them otherwise I would have bought a set from Roger no problems

I just got sick of second hand manifolds cracking one set didn't last a year and at a cost of purchasing them and then getting them installed ended up costing me $900 I had done that once already before so $1800 spent before before I finally said stuff this

I also waited with cracked manifolds for a year trying to get a set of manifolds made

I originally bought the Plans from XJR engineer then took them to a shop so if you are handy or know someone that is Andy will sell you the plans and you can make them yourself at a substantial saving only difference between my ready made and his is I developed the headers and bottom flange to be a direct replacement fit my headers also come with shortened studs so a very easy home install can be done by a pretty competent home mechanic that's where I spent a lot of money prototyping them

There should be no reason why any car should fail emissions without the front cats there is a second set of cats under the floor the air pump lights of these when you start the car to warm them up quickly so without the front cats the secondary cats light up quicker anyway you can also remove the air pump as well no need for it after you install the headers

As everything it just comes down to cost and as these cars are getting old most people don't want to spend the money on them

That's why roger didn't sell many plus when he was making them these cars where not that old so not that many had cracked and good second hand ones don't mean they wont crack I never had my ones repaired I replaced them with good second hand ones each time and they still cracked and pretty quickly I might add one set within a year and I average 10,000 k,s a year so do the sums on that

As for the 4 O2 sensors the rear O2 sensors are on the same wiring as the fronts you could remove the rear O2 sensors and there shouldn't be a problem or you could remove the front ones I could make a set of headers without front bungs for the front O2 sensors that would save money again
or you could make a set of these http://zero-signal.org/o2/O2bypass.html.htm

There are also various devices available that mimic O2 sensors and with adjustable devices might allow for some small tuning gains as well as well ask Andy he knows there is not much he doesn't know just a thought also remember our cars are getting old and most of the cats in our cars are probably past the use by date anyway

I did my headers because of the cracking manifold issue but did the exhaust system with new cats because my car had a issue with running overly rich and overly rich mixtures kill catalytic converters I also had Andy reprogram my ECU

I haven't done a big trip in my car but mixture of round town and highway I get 600 k,s to a tank I used to only get 450K,s same usage before all the mods I think I might see 700 on the open road on a trip not a bad improvement on an 18 year old car

 

All this talk of cracked manifolds and it failed the MOT with duff lambda sensors! We had sourced a second hand replacement downpipe to replace my old cracked one and we just left the lambda sensors in it. As they're basically consumables, I'll buy two new ones and if I can retrieve the two from my old downpipe I'll keep them as spares.

After some scrounging around I found two new ones (from two different suppliers) for about £100 inc VAT the pair.

Jaguar list price is £350 ex vat - each!

 

I get O2 sensors from these guysAir Flow Meters, Lambda Sensors & Other Cheap Japanese Car Parts very reasonably priced they are also the only ones with airflow meters brand new for XJR6 cars

 

I also wouldn't mind a new pair of ex. manifolds. The ones I bought are just with smaller cracks than previously. Now my car idles so hi that I can't even brake (at least it doesn't die)!

It's just a piece of metal! How hard can it be to make? It's not a damn processor!

 

I dont have idle issues. But can u spot the cracks by eye? Should I just.remove the cover and look?

 

I had a DSM wich also had cast iron manifold and it wasnt a problem to weld it. Why is thisone so hard or Impossible to weld apparently?