Thom

Using a 6 cylinder t5 will mean you have to get a crs bellhousing as the 6 cylinder t5 has a different length input shaft to a v8 one, the diff will be fine and the t5 will hold up reasonably well as long as you don't abuse it ( when I was a p plater I broke many of them with a warmed up 4.0l but they were pretty well abused)

No, do not use oil flush it will cause the same problems dumping kerosene in the sump would, the goal is to clean the engine gently and slowly, anything that rapidly speeds that process up is what causes problems, the only safe way to clean an engine fast is to dissemble it

Safest way to clean it if there's no metal in the filter is to use a higher detergent oil (like a diesel oil) and do 4 or 5 sub 1500km oil changes, it won't make the engine spotless inside but it will clean gradually and shouldn't dislodge anything big enough to cause damage, flushing fresh oil through the engine before firing it up with the new cam won't hurt anything and is a pretty good idea, make sure you use plenty of assembly/ break in lube on the cam and lifters when you install them

Flushing the sludge/ metal from the cam & lifters without pulling the sump/ cylinder head to clean out all the oil galleries and oil pump/ pickup will most likely be a death sentence for that engine, you can guarantee you will loosen and flush a large percentage of the gunk in the engine, but that's not the problem, it's what gets left behind that is now free to roam the engine until finds a nice oil gallery or oil pump pick up or oil return to plug up and cut off the oil supply to that area of the engine. Also if metal has been through the engine the oil pump needs to be inspected as the rotors and oil pressure relief need to be inspected for damage and the pump replaced if they are

Xe and xf stock exhaust centre section is supposed to be 2 inch for all models, with carby engines having a 1.75inch tail pipes and efi crossflows having a 2 inch tail pipe, 2.25 works really well for stock to mild crossflows if you want a little bit of noise without it getting annoying

It's not the "correct way" to do it but I've fitted one with self tappers before, if you wanted to do it a bit better than that I've used nutserts and then bolted it in

I think deans on it, only other thing it could be is a valve not seating

It may have had other problems I wasn't as good with carbs back then, as much as I thought I was at the time, but you can learn a little bit in 15 years, I do remember it making a huge difference to that car at the time, it made as much of an improvement as putting an efi cam in it and swapping the auto for a t5

When I was 19 I had an xf wagon I got from the original owner, it had 60,000ks on it it was a 4.1 and was the slowest car I had ever driven (I even pulled the plugs and measured the stroke to make sure it was a 250 and not a 200) turns out it had a webber from a 3.3 on it previous owner swore black and blue the carb was original to the car, I put a webber off a 250 on it and it made a huge difference

E series a/c compressor doesn't fit au accessory brackets, to swap to e series accessories won't help either, as the a/c compressor is is still too wide with the e series brackets (e series brackets also require a different timing cover, water pump and balancer than au) as dar as running a/c goes you would need to modify the passenger side rail to clear the pump, but if you aren't going to run a/c you can just use a shorter belt and remove the a/c pump all together

Xg or xh pano?, if its xg you have everything l, if its xh you'll need either xg engine mounts or modify some crossflow engine mounts, with either you'll need to modify the radiator mounts to suit the xf core support, you'll probably benefit from swapping the diff out of the donor car too, it isn't quite as simple as I've jut said but if you've changed an engine before it's not much harder, physically bolting running gear in is the easy part, swapping wiring looms, getting a shifter sorted and making the dash work is the hard part and may require a little bit figuring

If you xf already has a t5 it's almost a straight swap, the trans mount is different on e series, ,e series has a single bolt trans mount, all you have to do is drill you crossmember for the e series mount and swap your speedo transducer, the rest its the same

You'll need a xflow t5 bellhousing, 4.0l are different to xflow

Could be an improperly done brinnel (hardness) test

Here's an old video circa 2007 with my phone taped to the steering wheel running from zero to 180 kph (i was inventive back then) of my pick a part special 4.0 it made 144rwkw around this time, and it made 177 rwkw with a tune later on (video quality is representative of its time) it was in my xh ute with an ex taxi au short motor (from memory had more than 860,xxx ks), ef xr6 head (94 dt) ea cam, el bbm intake, super cat extractors, crow vernier cam gear, yella terra billet flywheel, high flow cat 2.5 inch exhaust, t5 and 3.45 gears, it was a lot of fun to an 18 year old me, I put over 180,xxxks on that engine before it let go when the stock valve train decided that 2 years of turning to 7000rpm was enough and it dropped a valve, after it was tuned the rev limiter was set to 7200rpm and it saw it every time it was in 1st gear (18 year old me was hard on the equipment) and sometimes more often than that, I wouldn't mind getting another e-series one day and replicating this combo, although it would be really fun in something lightweight like an xp falcon