camshaft broken

[tim littlewood]

My engine just faded, removed the cam cover to find the inlet side cam shaft broken by the front bearing mount.
How common are camshaft breaks?
Is there likely to be major damage, all valves under the cam have fully closed now I have removed the cam shaft.

[rgh0]

In a standard engine cam shaft breaks on their own are rare, more common in developed engines with higher lift cams and stiffer cam springs and more rpm. Race engines typically use longer sprocket bolts to reinforce the front of the cam to prevent breaks at the front bearing like you have experienced

A cam shaft may be broken if something else went wrong and caused the cam to jam so you need to try to find what caused the failure in the first place.

The bad news is the valves and pistons will have hit and you likely have major damage to a number of valves and maybe pistons and other related parts. The engine will needsa complete stripdown and check and replacement of damaged components

regards
Rohan

[tim littlewood]

thanks, according to the info I have on the engine, the original cams have been machined to fast road profile(L14 kentcams). All the valves seem to have free movement, is there any chance I got away without valve or piston damage?

[mark030358]

I would not have thought so. I would follow Rohan's advise he is spoy on with this kind of thing.

cheers

[ftsoft]

One of my camshafts was broken in half about 2/3 of the way down the shaft. The thing is, not only did it not damage anything, the car ran pretty well with it like that. Any way, I was lucky to find a used camshaft at RD.

[GrUmPyBoDgEr]

One of my camshafts was broken in half about 2/3 of the way down the shaft. The thing is, not only did it not damage anything, the car ran pretty well with it like that. Any way, I was lucky to find a used camshaft at RD.

The mind boggles

[elanbaby]

Hello,
I have come across a head which probably was distorted, because both cams didn?t turn freely by hand (no valves/ springs assembled). I guess a warped cylinder head is a good starting point to break camshafts...

Apart from Rohans advice I?d suggest to check (before reassembling) that both cams can be easily turned by hand.

Juergen

[types26/36]

Hello,
I have come across a head which probably was distorted, because both cams didn?t turn freely by hand

Or the cam caps were fitted in the wrong location/or caps from a different cyl head could have been fitted.

[elansprint71]

One of my camshafts was broken in half about 2/3 of the way down the shaft. The thing is, not only did it not damage anything, the car ran pretty well with it like that. Any way, I was lucky to find a used camshaft at RD.

So only one valve in one cylinder was not working, sounds reasonable, the spring pressure would push the valve closed, out of the way of the piston. Or am I missing something?

[billwill]

One of my camshafts was broken in half about 2/3 of the way down the shaft. The thing is, not only did it not damage anything, the car ran pretty well with it like that. Any way, I was lucky to find a used camshaft at RD.

The mind boggles

I suppose not altogether surprising, there would be nothing to stop the valve spring pushing up and turning the free end of the broken camshaft such that the valve shut itself. If it was the inlet camshaft that piston would have no further effect.

Had it been the exhaust camshaft that broke it might be different as there would be nowhere for the spent combustion products to go & I suspect they would come out of the inlet valve as soon as it partly opened, possibly setting fire to the carburettors.

[gjz30075]

I may be getting my sides mixed up but is it possible that the 'D' shaped head bolt washer wasn't positioned properly and the cam was rubbing on it? Could cause enough heat to do something nasty.

Greg Z

[elangtv2000]

I have seen a head that broke cams twice(!) First time they were replaced the head was not checked for flatness, and after the second time it was found that the head was pretty significantly warped. Turned out the head had been a Stromberg version that someone had welded some adapted Weber inlet manifolds to, which seems likely to have caused the warpage.
Might be good to check flatness, parallel, and cam saddle alignment.
Cheers,
Greg Tatarian
2 Elans

[tim littlewood]

thanks to all who have commented, I will keep you updated on what I find.

tim

[Jeff@Jae]

I actually had that happen on a Lotus Cortina and it occurred while trying to start it. The engine was locked up. I thought possibly the starter was locked up in the ring gear so I used a wrench to rock the crank back and forth and it would then spin on the starter. Still no start. I couldn't figure why it wouldn't start as I had just had a very spirited driving session a few days before. I cranked it over a number of times, checked spark, fuel etc. and finally figured out the the spark was out of time with the crank. Gave up and took the Elan to the vintage races. A few days later I removed the cam cover to see what was going on and found a slack chain and broken intake cam right where you discovered the break, at the first cam journal. Having seen this on racing engines and thinking I needed to bore, drill for a longer bolt on my next cam along with the special long bolt I started to remove the cylinder head thinking bent valves and found the culprit right away. The cylinder head bolt by #1 intake valve had popped the head of and lodged between cam and follower(tappet) bore edge ! This was a later style Kamax head bolt and it parted right where the thick washer abuts the hex head. The non radiused, sharp angled area under the head combined with the sharp edged washer resulted in a huge stress riser and popped off while coollin down after the hard run. Lesson, do not trust or use standard head bolts but instead use the ARP head bolts with a radius under the head and the radius top ID, ground finish washers. The amazing thing was that after all that turning the engine over on the starter none of the valves were bent ! The other nice thing was that upon checking the cylinder head over the valve guides (hone fit the valves very carefully) were a perfect fit to the valves after 40,000 very hard miles. A light lap in of the valves and small clearance adjustment, new ARP head bolts and we were good to go.
I would crack test cams before installing(they are old), do the long bolt trick on aggressive cams (those L14s are high lift, short duration and therefore violent on valve gear, so do those) and never use standard head bolts.

[RotoFlexible]

The amazing thing was that after all that turning the engine over on the starter none of the valves were bent !

I have a vague recollection of an Elan that broke its timing chain without damaging any valves - I guess it all depends where the camshafts stop. (This was Noel Poduje's street Elan, for those who were in New England in the '70's.)