Engine timing chain is broken

[TommyK]

so, finally we had the chance to take a first look at the engine. And in fact, the timing chain is broken.

will pull the engine out of the car in a couple of weeks and then looking further what happened to the pistons and valves.

Thought about replacing the cylinder heads with Edelbrock Performer RPM Complete Cylinder Heads as well the matching Edelbrock cam or a Comp Cams kit. Probably also getting a Federal Mogul rebuild kit with forged pistons etc. if the engine is anyway open.

Does anyone know if I have to swap my current Edelbrock Intake Manifold for the Performer RPM?

I don't want to make a race engine. just want to have a reliable, strong engine for the street...

But after today, it seems christmas won't have a lot of presents for rest of the family this year...

Now that's something you don't see every day.

Does the engine rotate?

 

[antipasti]

Now that's something you don't see every day.

Does the engine rotate?

If you mean the crank shaft? Yes it was turning.

 

[TommyK]

Now that's something you don't see every day.

Does the engine rotate?

If you mean the crank shaft? Yes it was turning.

It looks like the harmonic balancer broke and took out the timing chain or is it the other way around?

 

[basstrix]

Wow! I've seen broken balancers, but never a broken timing chain! Along those lines, I've seen the nylon teeth break off of the cam sprocket and jump teeth....many a timing belt stripped, but this is a new one.

I suspect you have more going on inside the engine (but I hope not). Please do keep us posted...I think there is some learning in this for us. Thanks for the update, by the way.

 

[piper62j]

All these members are spot on.. Seems the shop cannot pinpoint the issue due to a lack of experience with these 40+ year old engines. You stated the engine would crank over but not start, so that's an indication the crankshaft will rotate. Broken points don't make sense to me.. Never seen it happen..

An easy diagnosis is to crank the engine over by hand with a socket and ratchet on the harmonic balancer bolt with the distributor cap off.. If the rotor is turning, then the chain is still in place.. The cause of this problem might lay elsewhere..

 

[antipasti]

All these members are spot on.. Seems the shop cannot pinpoint the issue due to a lack of experience with these 40+ year old engines. You stated the engine would crank over but not start, so that's an indication the crankshaft will rotate. Broken points don't make sense to me.. Never seen it happen..

Hi piper62,

Actually the shop was right. The the chain is broken and the balancer got damaged as well. I've posted pics from the weekend when we opened the engine. Maybe the points got dmaged afterwards when I tried to start the engine a couple of times...

Thanks

Andreas

 

[Hemikiller]

Now that's something you don't see every day.

At this point, assuming the crank snout isn't damaged, I'd throw a cheap timing chain on the engine and do a cranking compression test. Whatever damage may have been done, is already done. It'll affirm or rule out if you have valve damage.

 

[antipasti]

Also time to look forward...

my thoughts and questions about the engine rebuild:

-> http://www.7173mustangs.com/thread-engine-rebuild-after-broken-timing-chain

 

[antipasti]

Hi all,

finally I made some progress with my engine. Last week we pulled it out and had a look inside. As I read lots of horror stories, I was expecting to see a worst case scenrio inside, since I really had not much luck yet with my car...

But in general I was surprised in a almost positive way!

Right Engine Side:

Left Engine Side:

On the left side there are some light marks where the valves "touched" the pistons 1, 2 and 4. But the valves seem to be relatively OK as at least nothing was broken apart. When I pulled out the pushrods, I was happy to find them still in good shape as they have not bent and the cylinders do not show any scratches.

Below some detailed pics on the affected pistons and valves.

Cylinder 1:

Cylinder 2:

Cylinder 4:

Will continue soon to disassemble the cylinder heads to check if the valves have been bent.

Considering the "minor" marks on the pistons, I was wonderig if I do need new ones - just to be on the safe side. Or if should "only" change the pistons rings as well as all the bearings and gaskets...

With regards to the the root cause of my current issue, I was wondering that the broken timing chain seems to be much thinner than the sealed power spare part I bought in the meanwhile. Has anyone seen comparable thin timing chains?

will keep you posted...

Thanks

Andreas

 

[Carolina_Mountain_Mustangs]

When you pull the pistons out inspect them. Measure the ring groves and check wrist pins and if everything is in spec. I would use them. Put new rings in and have them hone the cylinders just enough to break in the new rings. You can put the valves in a Vee block and check for bent heads and stems. A check of the valve guides might need bushings added for wear and do a valve job. The crank will obviously be inspected and ground or polished and new bearings. You have the flat top pistons and not dished which is better for compression.

The broke chain is much smaller for sure. Probably had so much slack in it that it rode up the gear teeth and broke it.

Rebuilding and engine is always lots of decisions of where to stop. Some have to replace every thing but if the parts are in spec. no cracks or damage then use them.

 

[computercarguy]

I personally wouldn't reuse the struck pistons as the edges of the dent could become a 'hot spot' and possibly lead to pre-ignition. I also wouldn't take a chance on a valve that has made contact with a piston even if it looks good, tests as straight and true. Stress on the valve could lead to failure down the road.