On Saturdays.........

[Twiggy]

... I "work" in my local garage, an independent repair specialist. I say "work", but because I`m arthritic I can do little more than tidy

 

up, wash up and  clean  the kitchen and toilets. It makes a grand change from working in my garage making belts though, and the

 

lad who owns it is very knowledgeable and a thoroughly nice chap. There is always something interesting being repaired............

 

For the last 3 weeks, there has been a 1.8 61 reg diesel Focus on one of the ramps with the engine in bits. It was sold by a local

 

dealer a couple of months ago, but the cam belt snapped............. so the AA initially recovered it to a repair shop  where it had the

 

head skimmed, new valves, and a new cam belt kit fitted.  Regardless of what they did, it would not start and eventually it finished

 

up with us.The head came off, everything was checked carefully and it was rebuilt. Still it wouldn`t start, and a week passed with

 

all sorts of attempts being made by the three mechanics to persuade it into action. Nothing doing. They decided (correctly)

 

that it was a timing problem, but what ? Eventually they looked carefully at the camshaft - very carefully - and discovered that

 

the cam lobes were mostly pointing in the wrong direction. Now, I always thought, (as they did) that the camshaft was cast and

 

machined from one solid piece of metal. Not in this case though: the lobes had been sweated (?) on to the shaft, presumably

 

because it was easier and cheaper than machining from one solid piece. So, when the cam belt snapped, the valve stems forced

 

the lobes round on the camshaft. Result was that the timing was so ridiculously out that it would never have started. A new

 

camshaft was fitted, and it cracked up first time. However it smoked badly and missed when revved, so still not solved. Perhaps

 

turning it over on the starter with the damaged cam shaft has bent the valves ? Any suggestions ?

 

 

[PiperCub]

If what you say about the cam lobes being effectively moved around the camshaft itself is true then I'd say you're right, the mistimed cams have opened the valves at the wrong point in the cycle and some of the valves are bent again in the same way as when the belt snapped. Think the head may be coming off again. 

[Cavcraft]

Any suggestions ?​

 

 

http://www.cartakeback.com/​

[BavarianRetro]

Are you sure about the cam??

 

Presumably it runs in bearings? Presumably there'll be lobes between two bearings? How did the manufacturer get them there?

[Supernaut]

Any suggestions ?​

 

 

http://www.cartakeback.com/​

[Twiggy]

Are you sure about the cam??

 

Presumably it runs in bearings? Presumably there'll be lobes between two bearings? How did the manufacturer get them there?

 

The camshaft does run in bearings rather like big end ones, you place the shaft on the lower bearings and then bolt the caps down.

[Asimo]

Built up camshafts are a thing these days. I think Jaguar use them amongst many others. Allows cheaper manufacture and more metallurgical options.

 

Diesels break camshafts or rockers because the valves are vertical, ie the piston wacks the valve square on, so that rather than bending the valve as would happen in a petrol engine with angled valves, the valve pushes hard and straight against the cam (or rocker if there is one) and something breaks.

[AMC Rebel]

Now, I always thought, (as they did) that the camshaft was cast and

 

machined from one solid piece of metal. Not in this case though: the lobes had been sweated (?) on to the shaft, presumably

 

because it was easier and cheaper than machining from one solid piece. So, when the cam belt snapped, the valve stems forced

 

the lobes round on the camshaft. Result was that the timing was so ridiculously out that it would never have started. 

 

 

Built up camshafts are a thing these days. I think Jaguar use them amongst many others. Allows cheaper manufacture and more metallurgical options.

 

 

 

You learn something new every day - this place is great.

[Squire_Dawson]

So that passes as engineering these days? Disgusted but not entirely surprised.

[tommotech]

Cars are built down to a cost, sadly not up to a standard.

[BavarianRetro]

Yep. Never knew that. Not entirely surprised.

[twosmoke300]

To be fair it only failed because the cambelt snapped in the first place .

[AMC Rebel]

To be fair it only failed because the cambelt snapped in the first place .

 

I remember when cambelts started replacing chains - it was because they were quieter, lighter and would last the life of the engine.  Now as long as they last the 3 year warranty period that's plenty.

[twosmoke300]

Cambelts were never said to last the life of an engine !

[Guest Hooli]

They last the life of any engine they snap in....

[panhard65]

Last year I had an old bloke call in with a cam out of a Transit. It was a right mess badly worn and with one lobe floating about. He wanted it welded in place so he could get it running and flog it. I was very reluctant but did it for him as he was convinced it would work. It was a bit of guess work where to weld the lobe, but I never saw him again so maybe it worked.