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They seems to o be TTY bolts. I feel it would be safer to replace them
When I looked into it I found information which supported the fact that you can use these TTY bolts up to three times.
The only bolts I renewed during my rebuild of these engines were the head bolts.
Do you have the engine out yet? Do you have a lot of experience doing this kind of work?
Last edited by kansanbrit; Jul 7, 2025 at 07:57 AM.
Thanks a lot for the detailed info - really appreciate you taking the time!
I’m honestly surprised there isn’t a standard kit available that includes all the required bolts and studs for this job, especially given how common bearing service is becoming on these engines.
TTY bolts, or Torque-to-Yield bolts, are specialized fasteners designed to stretch slightly when tightened to their yield point, achieving a consistent and precise clamping force. They are commonly used in automotive engine assembly, particularly for cylinder heads, and are engineered to stretch within a controlled yield zone to maintain optimal clamping force. These bolts should not be reused as they lose their ability to properly clamp once stretched.
TTY bolts, or Torque-to-Yield bolts, are specialized fasteners designed to stretch slightly when tightened to their yield point, achieving a consistent and precise clamping force. They are commonly used in automotive engine assembly, particularly for cylinder heads, and are engineered to stretch within a controlled yield zone to maintain optimal clamping force. These bolts should not be reused as they lose their ability to properly clamp once stretched.
Are you an engine builder or did you just Google that ?
Thanks a lot for the detailed info - really appreciate you taking the time!
I’m honestly surprised there isn’t a standard kit available that includes all the required bolts and studs for this job, especially given how common bearing service is becoming on these engines.
I believe Velocity AP now sells head stud and mains stud kits for these engines.
When I looked into it I found information which supported the fact that you can use these TTY bolts up to three times.
The only bolts I renewed during my rebuild of these engines were the head bolts.
Do you have the engine out yet? Do you have a lot of experience doing this kind of work?
as I said before, @kansanbrit knows what he’s talking about.
and YES, you can reuse TTY bolts. A lot of builders will stamp them every time the torque then so they can count how many times they’ve been used. There are also ways to check for the amount of “stretch” to see if they’ve passed their limits.
as I said before, @kansanbrit knows what he’s talking about.
and YES, you can reuse TTY bolts. A lot of builders will stamp them every time the torque then so they can count how many times they’ve been used. There are also ways to check for the amount of “stretch” to see if they’ve passed their limits.
When I looked into it I found information which supported the fact that you can use these TTY bolts up to three times.
The only bolts I renewed during my rebuild of these engines were the head bolts.
Do you have the engine out yet? Do you have a lot of experience doing this kind of work?
I bought a project car with 63k miles. It had some concerning signs: dusty metal particles in the oil filter, about 3 quarts of oil missing, and a strong fuel smell from the oil cap. I started the engine once — it didn’t sound too bad considering the low fuel pressure on Bank 1 and misfires on cylinders 5–8. There’s also a strange squeaky noise, especially when the engine is about to stall. I’m hoping it’s just a pulley or belt-related issue.
According to the vehicle history, the HPFP(s) was replaced. I also found an old fuel injectorin the trunk, so someone clearly tried addressing fuel-related problems.
Given the condition of the oil and filter, it seems reasonable to assume the engine might be in bad shape despite the low mileage. My plan is to pull the engine, inspect timing, and verify the HPFP was installed correctly. While it’s out, I’ll also check or replace the timing chains and inspect/renew the rod bearings.
As for my experience - I have none when it comes to this level of engine work. I’ve done some projects on BMW engines, but nothing this deep involving internal components. That’s why I have a bunch of (probably silly) questions and I’m doing as much research as I can to figure out what needs to be done and what might go wrong.
It's a pretty big job on that vehicle particularly, Big, big job actually. Are you aware that the front differential is mounted on the sump on that engine? I wouldn't do it again. I would put new oil and filter in it and see what happens when you drive it. Fuel will get into the oil if one of the HPFP is broken and they break easily when being installed if not done properly.
Last edited by kansanbrit; Jul 7, 2025 at 09:32 AM.
The plan is to disassemble the front end of the car, support the transmission with a jack, and pull the engine using an engine crane. That should give me full access to inspect everything while the engine is out.
The plan is to disassemble the front end of the car, support the transmission with a jack, and pull the engine using an engine crane. That should give me full access to inspect everything while the engine is out.
Good luck getting the engine disconnected from the transmission in that situation. And don't forget, it's always much harder to put things back together than it was to take them apart.
Last edited by kansanbrit; Jul 7, 2025 at 09:40 AM.
you can get rod bolts they’re the same as the aj26 and later. i have a bucket of them somewhere. $15 a piece x 16 is almost the price of decent used rods. use a couple from your known bad rods to save cycles on the bolts that will be used for final assembly.
my only pro tip is do not attempt to lower the subframe on an L405 range rover. ever. ever
you are NOT equipped to do the job. front end has to come apart and you need to use a crane
I found this post from 2021. Did anyone try these?
Originally Posted by davetibbs
See attached specifications which contains torque specs for the main bolts listed above but also the connecting rod bolts.
A lesser-known fact: the custom ARP bolts I purchased for my connecting rods were actually for the 4.2, but despite the design of the 4.2/5.0 conrods being different, the bolts used are actually the same specification, meaning you should still be able to order 4.2 bolts from JLR - they generally don't list any internal parts for the 5.0 block for purchase.
Are you an engine builder or did you just Google that ?
I've built a few engines over the past forty odd years, I picked this knowledge up when Blue printing one.
always replace these bolts, If torqued properly they would have stretched to there given tolerance which means torqueing existing one will over over do it, and I wouldn'twant to be going through the process off stripping the engine down again with all the effort it takes in the first place
My reply was taken from the internet, because it was easier to digest
Hello everyone! I have read this thread and would like to add to it. I purchased a 13 Jag XJL with the 3.0. A week after arrival, I knew it needed a rebuild. I spent ( months getting parts, having heads and block and machined, and hardest part was getting information for torque and assembly. They certainly don’t want anyone rebuilding these. Anyway, in November of last year is when I got it. And now it runs quite nicely. Here are some photos I took while working on it. One of the hpfp was broken and needed replacement as well. After taking the heads off as a result of a blown headgasket, I noticed bigger issues. Number two piston had a HOLE blown right through its side. The cylinder bore of that piston had a visible massive gash on it. And that needed to be cut down and resleeved. Seeing all this damage, I had to go for a rebuild.
[img alt="I decided to change all 6 pistons, main bearings, conrod bearings, and new headgaskets and bolts. I also decided to do a cooling system overhaul as that is a very big weak point on these engines. I went all aluminum even for the thermostat housing. New timing stuff like chains, tensioners, guides were also replaced
*Side note on the timing on these, the timing chain tensioner arm is known for forming a divot exactly at the point where the tensioner pushes the arm. New ones have steel buttons."]https://cimg7.ibsrv.net/gimg/www.jaguarforums.com-vbulletin/2000x1504/img_0630_3faa16a774a0832aa8feaa758b4713097674c1c2. jpeg[/img] I decided to change all 6 pistons, main bearings, conrod bearings, and new headgaskets and bolts. I also decided to do a cooling system overhaul as that is a very big weak point on these engines. I went all aluminum even for the thermostat housing. New timing stuff like chains, tensioners, guides were also replaced *Side note on the timing on these, the timing chain tensioner arm is known for forming a divot exactly at the point where the tensioner pushes the arm. New ones have steel buttons. I also decide the completely lap all valves and clean out all the ports. It was such a mess from all that carbon buildup. It looked like a brand new engine when it was all completed but it took almost half a year to finish. I put in in spark plugs and changed one faulty injector that did not have a consistent mist spray.
I can post a video of it running and you can be the judges as to how it sounds. I can provide a lot more details if you have any questions. I took a lot of pictures, including diagrams of where everything goes if anyone ever needs it. Thanks for reading!
