Can you resuse a camshaft whereas the timing belt broke?

[Mordan]

Hey

I went to see BMW parts and the guy is selling a M20B25 cylinder head with all the rocker arms broken. He says the lady didn't change the timing belt on time.

I'm considering buying it for 100 dollars for the camshaft whose lobes are way better than mines. Is it wise? As a bonus, he says the head doesn't have any cracks.

thank you.

Mordan

[E34-520iSE]

Have a good look at it first. If there's valve damage etc it'll be $100 for a scrap piece of aluminium. Can you not get a cheaper cam from elsewhere?

Regards,

Shaun M

[whiskychaser]

Check local scrap price for aluminium - you might get your USD 100 back if you weigh in the head. So you get the cam for free:D If you can find a place that will test the cam and confirm its in good shape for a few dollars it may be worth a go. But if you phrased the question ' should I use bits out of a wrecked engine in mine?' I think you know what the answer would be;)

[Mordan]

Have a good look at it first. If there's valve damage etc it'll be $100 for a scrap piece of aluminium. Can you not get a cheaper cam from elsewhere?

Regards,

Shaun M

to be honest I haven't seen many M20 heads already. But I can recognized good cam lobes from bad ones.

There is valve damage obviously. The pistons hit them and the valves broke all the rocker arms in 2. I'm buying it for the cam and perhaps the head.

Does valve damage necessarily mean damaged valve guides and valve seats?
I would think so, but again I'm a newb.

Cheers

[whiskychaser]

Does valve damage necessarily mean damaged valve guides and valve seats?
I would think so, but again I'm a newb.

Cheers
You can see if the seats are damaged once the valves are out. But you wont know if the guides are damaged unless you try a new valve in there. When you are taking a head apart you are supposed to keep the valves in strict order and put each one back where it came from. Its to do with how they wear together. If you are swapping heads you cant do that.

[Mordan]

You can see if the seats are damaged once the valves are out. But you wont know if the guides are damaged unless you try a new valve in there. When you are taking a head apart you are supposed to keep the valves in strict order and put each one back where it came from. Its to do with how they wear together. If you are swapping heads you cant do that.

k. I understand. keep the valves where they belong to.

but if I swap heads (provided the seats of the 'new' head are ok) and I can't reuse the valves of the 'new' head because they are damaged, I will have to buy new valves and guides right?

[Ross]

Having valve to piston "interferrence" is no reason to write off a cam, you said you know how to inspect one. Having bent valves is no reason to write off the guides either.
If you mix up valves they can be lapped into another seat provided they aren't too deep or to proud in the seat.
Sounds like a decent deal. If the head turns out junk expect at least $.65/# for it.
Time to have a look at the belt on my M20.

[Mordan]

Having valve to piston "interferrence" is no reason to write off a cam, you said you know how to inspect one. Having bent valves is no reason to write off the guides either.
If you mix up valves they can be lapped into another seat provided they aren't too deep or to proud in the seat.
Sounds like a decent deal. If the head turns out junk expect at least $.65/# for it.
Time to have a look at the belt on my M20.

":).. yea when I saw head, it was scary. all because of a belt. They say it is even worse on the M40. one guy lost his engine because he failed to replace the belt at 81 000 km while he should have done it at 80k


Thx for the advice.. aren't guides removable ? when i read the realoem site

http://www.realoem.com/bmw/showparts.do?model=BB21&mospid=47290&btnr=11_1914&hg=11&fg=15

they say the guides cannot be manufactured anymore? Wth?

[whiskychaser]

":)..
they say the guides cannot be manufactured anymore? Wth?

You should be able to get valve guides though you wont be able fit them yourself. Check with your local machine shop. You can pick up reman. valves here for about £6 each. Not cheap but Mr BMW wants £25!! Apart from the cam not being in good shape, whats wrong with the old head?

[Mordan]

You should be able to get valve guides though you wont be able fit them yourself. Check with your local machine shop. You can pick up reman. valves here for about £6 each. Not cheap but Mr BMW wants £25!! Apart from the cam not being in good shape, whats wrong with the old head?

99% chance that at least one valve seat and guide has to be redone.

otherwise, it is good condition. good compression.

it is the story of the broken rocker arm, see other post. we replaced it and all went well at the first drive. but when head cooled down and engine was restarted, an horrible sound came from the head/rocker arms.

[whiskychaser]

99% chance that at least one valve seat and guide has to be redone.

otherwise, it is good condition. good compression.

it is the story of the broken rocker arm, see other post. we replaced it and all went well at the first drive. but when head cooled down and engine was restarted, an horrible sound came from the head/rocker arms.

Sorry, I didnt make the connection. As the old cam is not in good shape, the valve gear is suspect and you may have damaged valves/guides, it sounds like there isnt anything to salvage from the old head. But you wont know the extent of the damage until the old one is apart and you have identified the cause of the problem. I'd keep and eye out for a complete head just in case