XJ XJ6 / XJR6 ( X300 ) 1995-1997

If timing chain breaks = bent valves ?

 
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Old 12-18-2018, 02:05 PM
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Default If timing chain breaks = bent valves ?

I am about to go look at a 1996 XJ6 VdP and the previous owner claims the lower timing chain has broken. He says he pulled the cam cover, turned the engine over with a socket on the crank and the cams did not move with the crank.

If this is indeed true, is the AJ16 engine an interference engine or not? I.E. if a timing chain breaks while the engine is running even at idle, will the pistons hit the valves?

I have searched here and so far I have not found any posts that mention any broken timing chain issues. Lots of posts about noisy timing chains due to tensioner or guide problems but nothing about actual broken chains.

Thanks in advance
--
Steve
 

Last edited by JensenHealey; 12-18-2018 at 03:37 PM.
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Old 12-19-2018, 02:23 AM
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I believe it is an interference engine. But there is never any interference. Let's ask Bob if he's ever seen an AJ16 with a broken chain. Bob?

If this has happened on the car you are going to see, we want to know about it please. I'd assume it would be a parts car then.
 
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Old 12-20-2018, 01:25 PM
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I do not understand what you mean by "it is an interference engine. But there is never any interference."
Can you please explain this?
Thanks
--
Steve
 
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Old 12-20-2018, 06:48 PM
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By interference is when the valve timing is so far off one of the valves may be down as the piston comes up and they hit each other causing much damage

This while the valve is fully intact and not broken but the impact results it proceeds to be and gets worse from there

OH BOY DOES IT GET WORSE

Some pistons have Scallop. cuts on the top of the piston to prevent this in design

 

Last edited by Lady Penelope; 12-20-2018 at 07:13 PM.
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Old 12-21-2018, 01:03 AM
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Originally Posted by JensenHealey View Post
I do not understand what you mean by "it is an interference engine. But there is never any interference."
Can you please explain this?
Thanks
--
Steve
I'm sorry for the confusion Steve. The timing chains "almost never" break. Hence, no interference! I suppose it is possible under certain circumstances. That's why I asked for you to let us know if you actually found a car with a broken one. It would be extremely rare. A more likely scenario is if someone was doing some work on the timing chain system and made some mistakes, which could then lead to engine disaster. But yes, valvetrain damage would occur if a timing chain broke (or jumped a few teeth too many).
 
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Old 12-21-2018, 06:58 AM
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Yes, I do completely understand what an interference engine is and I am familiar with valve pockets in pistons.
I was just confused by the "there is never any interference" statement.

What I find strange is the seller claims there is only 70K miles on the car.
I don't know how a timing chain would break on a motor with only 70K unless some really strange condition occurred.
In theory he is supposed to let me look at the car today so I guess I will find out,
He says he had started to take the motor apart by removing the cam cover, radiator and etc but had to stop due to medical conditions that prevented him from doing further work.
 
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Old 12-21-2018, 08:01 AM
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The owner may have been confused with valve chain rattle before the tensioner takes up the slack with oil pressure

There is a TSB on a revised tensionor and there is a oil viscosity recommendation

http://www.jagrepair.com/images/TSB/...er%20Start.pdf

Could be the original tensoner is bound up with oil tarnish and can be freed up with some oil treatment like Rislone that frees up old school hydraulic expanding lifters on ford engines that have lifter rod coming up from the internal cams before they designed them to place the cams overhead

has worked for me on other old school engines

You can buy a bottle at the local parts store and put it in during test drive and let it work things loose over time

Broken oil pump ?

To see if the timing chain is a tooth off , pull the valve cover and look for the flats on the cam shaft toward the front gear and as your rotate the engine around to the timing mark with a 34 mm socket ( 34 works but it may even be a 33 mm ) on the crankshaft nut

No special tool needed , just your eyeballs

If you dontt have a 34 mm socket you can remove the plugs to releave compression and with gloves spin a pulley around to your point of interest

The timing mark on the crankshaft pulley should be noted in the TSB on the PDF or this new engine DPF below :

# 1 cylinder at top dead center is the timing mark , see page 26 of pdf below

Editing complete and good luck with your inspection
 
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Last edited by Lady Penelope; 12-21-2018 at 10:22 AM.
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Old 12-22-2018, 08:47 AM
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The seller already disassembled the car so no test driving is now possible.
The rad, cooling fans and other pits are all in the trunk of the car.


Removed parts in trunk

Cam cover removed
 
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Old 12-22-2018, 09:11 AM
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Quote: "I am about to go look at a 1996 XJ6 VdP and the previous owner claims the lower timing chain has broken. He says he pulled the cam cover, turned the engine over with a socket on the crank and the cams did not move with the crank".

If the above is true then something is broken as the cams should rotate as the crank is rotated.

This statement would not apply in that case: Quote : "To see if the timing chain is a tooth off , pull the valve cover and look for the flats on the cam shaft toward the front gear and as your rotate the engine around to the timing mark with a 34 mm socket ( 34 works but it may even be a 33 mm ) on the crankshaft nut".
 
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Old 12-22-2018, 10:30 AM
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Talk about price negotiating leverage !!!!!

I got mine for $ 1,300

Depending on the other factors on the car condition

in it's condition you can remove the front casting and see if maybe a D clip sheared on the chain sprockets

You can bring the alignment flats on the cams and see if they line up

Protect the cam lobes as they rust easily when exposed

Put the engine back together and crank it up

There is a special tool to putting the harmonic balancer on but some have just bull dogged it but is important to torque the nut to a very high value

A replacement AJ16 engine runs about $ 500 as a worse case scenario

Still need a determination of weither it is a interference engine and the ultimate thing would be to pull the head

There is a TBS on using the head bolts twice and a stamp on the bolt head indicating it's been done , if followed

In practice I don't know if it's a good idea as they stretch but it gives you information now and can be replaced later

http://www.jagrepair.com/images/TSB/...ad%20Bolts.pdf

There is a overheated AJ16 engine in Kansas City that is a candidate to pull certain parts off the core engine

Some people would know more then me on this matter like Motorcarman
 

Last edited by Lady Penelope; 12-22-2018 at 11:12 AM.
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Old 12-22-2018, 11:39 AM
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The seller and I agreed on a price of $525 but I have to haul the car from northern New Jersey back to Youngstown Ohio
 
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Old 12-22-2018, 11:47 PM
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Good luck with it! Definitely worth the $525 in my opinion. I picked up mine for $400 as a non runner but it was all in one piece aside from the glove box.
 
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Old 12-23-2018, 01:48 AM
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You can most likely find a parts car within 100 miles of your home for that same price. Not worth hauling that hulk cross country. Why did he disassemble it? The whole story about the timing chain seems like blowing smoke. If the cams didn't turn when he turned the crankshaft, he would have had interference and the crankshaft would not have been able to turn anymore. Nevertheless, seems like that car will never run again so I hope you didn't intend to try.
 
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Old 12-23-2018, 04:16 AM
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Originally Posted by SleekJag12 View Post
You can most likely find a parts car within 100 miles of your home for that same price. Not worth hauling that hulk cross country. Why did he disassemble it? The whole story about the timing chain seems like blowing smoke. If the cams didn't turn when he turned the crankshaft, he would have had interference and the crankshaft would not have been able to turn anymore. Nevertheless, seems like that car will never run again so I hope you didn't intend to try.
I think you're being a little harsh about it personally. I see alot of hours to be spent but I don't believe it should be cast aside as parts. Like others said even a used replacement engine isn't too expensive a venture.
 
 
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