pistons and valves contact

[alan.barker]

I am sure you will have some bent Valves.
Organise someone with Twink knowlege to oversee the work.
Alan

[rgh0]

To break a cam with the engine running inevitably means piston to valve contact. If no sign of contact you need to look further into the problem I think

cheers
Rohan

[checkrail]

In my humble opinion the fact that the EX sprocket bolt was hanging by a thread at 1000 rpm caused the jamming and snapped chain. The next stage is cleaning and stripping the head for the machinist;

Regards John

[Phil.C60]

That may well be the case John, but when the chain snaps, the cams stop moving. At this point at leas two of the valves will be quite a long way open. The bottom end will continue to revolve due to inertia, and he pistons are extremely unlikely to pass the valves without touching. I seem to recall that you also cranked the engine over on the starter after the failure which will have the same consequences. I am fairly sure as is Rohan that there will be some bent valves, they will all need to be checked as you strip the head. Make sure you keep everything scrupulously in order: if you find one or more bent valves you will then know which pistons to inspect more closely. I still think you would be better off in the long run removing the engine from the car and inspecting it thoroughly.
Regards Phil

[HCA]

In my humble opinion the fact that the EX sprocket bolt was hanging by a thread at 1000 rpm caused the jamming and snapped chain. The next stage is cleaning and stripping the head for the machinist;

Regards John

John - this saga is heart wrenching to the extreme!

These engines have bomb proof bottom ends but as with all DOHC Hemi design, a very delicate top end. Coupled together, blistering performance. But when they break, they break big time.

As before, I urge you to listen to these guys when they say you have had piston-valve contact. They have tee shirts galore on the subject. One day you will join them and can advise others, but please, please, listen to them to get it...

[checkrail]

Cleaning / checking the head, no.2 inlet valve is bent,
its proud of the head and you can tell by the angle, its proving difficult to get the spring compressure on.The pistons are midway in the block and you can see a very slight mark on no.2 where the valve has touched

John

[Phil.C60]

John: don't be tempted to try and straighten it or knock it back towards the seat. You may be able to shock the offending valve retainer off by using a piece of tube ( or a long socket. ) in the retainer and giving it a sharp blow with a hammer. You may have to play "hunt the collets" afterwards! When you do get the valve out, you will need to check the bottom of the valve guide for damage....
Regards Phil

[rgh0]

Did you check the alignment of the tensioner sprocket with the chain ? The carrier can twist and this possibly happened when the chain was broken in the initial incident

regards
Rohan

[2cams70]

Did you check the alignment of the tensioner sprocket with the chain ? The carrier can twist and this possibly happened when the chain was broken in the initial incident

regards
Rohan

I think checkrail has created another thread for the part 2 saga. This is part 1. Hopefully there won't be a part 3

[rgh0]

Yes i went back here to see if he had changed the tensioner during his last thread, given his current problem with noise from the tensioner area and posted here by mistake. i will repost in his current thread

cheers
Rohan

[checkrail]

I'm still struggling with the chain noise, just to recap new parts are
front cover, chain. brass carrier and pin tensioner pad
With the cams removed I can pull the chain taut against the pad with one hand whilst turning the crank with the other. The chain is not fouling anywhere and I can get the jackshaft to rotate, but all the time there is what sounds like the chain on a sprocket, which only leaves the crankshaft one.
With the cams fitted and rotated , of course the noise is still there.

Sorry you must be fed up this topic John

[gjz30075]

Is there any way you can post a video of this noise? You'll have to put the video on a hosting site
and give us a link.

[Hawksfield]

John

First can you record sound and vision.

You say you can rotate the crank and there is still the noise, that implies that something
at the lower level is causing noise this either the rotation at the crank or at the Jackshaft sprocket, Let the EX side chain drop down and pull IN side chain backwards turning the jack shaft only, this may tell you which of the two sprockets the sound comes from.

Its very likely that you will have to strip down and inspect as its not easy to see what going on in that area.

John

[h20hamelan]

120 vs 122 link chain?
Is your tensioner maxed

[checkrail]

I have plenty of thread left on the tensioner, the replacement chain from Sue Miller fitted easily.
I am certain the noise is from the crankshaft area.

John