Asked another way, i'm I at risk of serious engine damage if timing belt snaps. I know on my Ferrari 308 its a major risk and is why diligent maintenance is required.

This Jalopnik article made me wonder about the jag

Here's What Happens When Your Timing Belt Snaps And How To Fix It

 

Don't all the V12s have chains?......can't say that I've ever read/heard of any chain failures on them, or the I6 motors.....perhaps the eventual break down of the "plastic" adjuster will cause a serious problem, other than noise and poor running.

Others more knowledgeable will/should chime in.

Rob and Chrys.
2006 X Type Sport Wagon.
1987 XJ6 Daily driver.

 

the head is pretty flat and the valves definitely drop into the cylinder. the v12 is definitely an interference engine.

The chains are pretty slick on it though, it isn't something that will just randomly break on you. Timing belts NEED to be replaced at regular intervals or something is going to break. This is not something to have on your mind when driving an XJS or XJ12, just isn't going to happen.

EDIT: didn't notice your post, the v12 uses double roller chains, they aren't just going to break. To answer your question, yeah you do risk serious damaged if it breaks, but worrying about that is like saying "do i risk serious damage if my main bearings turn to dust?"

 

Do you say shouldnt be worried because auto trans typically keeps RPM's very low?

 

I can tell you from experience, turning up your V12 isn't going to break the chain. I drove my 71 E Type like I stole it. Turned it 7K almost every time I drove it. Loved to hear that V12 scream. I have experienced a drop valve seat, but have yet to hear of anybody braking a chain. Tensioner maybe, but not the chain. Also know one guy, that drove his V12 with a loose chain, (unknowingly???) for so long it, it wore a hole in the cover. Having built a couple of these engines, and having driven them for a long time, I find it very hard to believe it wasn't noticable.

 

timing belt engines are going away,design is for chains, double row last for 1/2 million miles!

Ferrai was following the crowd back then most new ones are chain now!

 

I installed a TREMEC 5 SPEED IN MY 90. So, Revs are not an issue with the automatic. The engine was designed for high revs.

 

Mike did you install yourself?

 

Sure did. I started with a Keisler kit. in 2003.


I think they went belly up.


Walt Osborne at Vintage Jag at www.vintagejag.com can help you if you are wanting tackle a swap in your car.