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replacing timing chain without removing the head ?

17K views 5 replies 6 participants last post by  DAVID NEWTON 
#1 ·
did anyone replaced the timing chain without removing the head , i removed the timing cover and the cam sprockets, but the guide of the chain sits in the way to remove the chain, is this correct or am i missing something ?
 
#2 ·
Yves,
it is possible (just) to replace the timing chain without removing the cylinder head, but it is very difficult!! I had mine done this way to save a bit of cash, but in the end the head had to come off to replace worn valve stem seals. The consensus of opinion in the UK is that you might as well do both jobs at once.
 
#3 ·
The way I've seen duplex (thank God!!!) chains replaced is to de-tension the chain, then press out a pin on the old chain (chain breaker here) and attach the new chain to the old one and then have someone turn the motor over by hand. The new chain will feed through, then simply disconnect the old part and toss it...Be VERY careful that you don't let any cogs jump by letting go of either side of the chain...

One thing, duplex chains (the 911 has them also) rarely wear or break... Single chains are a completely different matter; I've seen a Volvo V-6 (this was in the 1980's) with ca 7000 miles come in with a broken cam chain that caused 3 smashed pistons (we were doing warranty subcontracting for the dealer on this one.
I don't know why single row cam drive chains are put in modern motors-they are a major problem waiting to happen.
 
#5 ·
With the M88, S14 and S38 engines with single timing chain, they must be replaced before 100k miles (160k km), otherwise they break. This is not a ferrytale, but a hard fact due to the much higher revs these engines are used compared to the M30 engines.

I recently looked at a 1983 M635CSI with 180k km for sale at a German BMW dealer and I could hear the chain clattering in such way that it needs replacement immediately. If the tensioner cannot compensate the increased chain length anymore, the valves are likely to hit the pistons.

BMW did not switch to duplex chains for the S38B36 and S38B38 engines for nothing. Also the engines for the E36 M3 (both 3.0 and 3.2) litre have duplex chains. With the duplex chains these engines are far more durable allthough they must be replaced anyhow at 300k km when the car is used more often. But at 300k km you need a complete engine averhaul anyhow.

Next to my E34 M5, I also have an E32 735i with the M30 engine with single timing chain. It is true that with this engine there are allmost no problems with the single chain. With the cylinder head revision of last februari, my dealer trusted the chain enough to fit it again after 140000km. But with your Alpina, I would be more carefull. Like the M engines, the revving accelaration speed is much higher than for the standard M30 engines.

With best regards,

Raymond
 
#6 ·
Gerhard
something completely unrelated, but saw your black b10 biturbo in the owwners gallery and liked the wheels. i also have a bi turbo number 389 and would like to put similar wheels on. could you please tell me the make and type so that i can try and find here in switzerland.
thanks brgds
david newton

Originally posted by Gerhard:
BMW change from duplex to singelchain in the M30 engine 1979 i think. And I never heard they have problem whit the singelchain.

Gerhard//Alpina BiTurbo whit singelchain !
 
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