Timing Chain Replacement with Master Link?

[craig.wilson1]

I'm sure there are some threads on the site addressing this, but my searches haven't turned up what I'm looking for.
I'm in the process of putting my 1979 911SC Engine back together. I didn't split the case and the engine is currently on the stand with only the P&Cs in place. Heads and Cam Boxes haven't been installed.

I'm planning on replacing the original timing chains with chains with the master link. I've seen the Pelican article where chain guides, sprockets, etc. were removed and a "ruler-like" tool was used to guide the chain onto the Intermediate Shaft sprocket.

I'm wondering why I can't just leave the chain ramps in place, break the original chain, attach the new chain to it and just rotate the crankshaft to feed the new chain on, then once it's through, detach the old chain and "close" the new chain with the master link.

I'm sure I'm missing something, hoping for some advice.

[john walker's workshop]

That's the easy way.

[PeteKz]

Why are you replacing the chain?

[craig.wilson1]

Just thought it would make sense to replace the chain (at 125K+ miles) given that it's relatively inexpensive and accessible. Will be replacing the chain ramps as well.

[PeteKz]

IMO, chains and sprockets don't wear quickly. In other engines on which I've worked, chain replacement is common, but on these engines, with the double row chains, I have not observed significant wear of the chains or sprockets at 100K+ miles. That's of several dozen disassembled SC and Carrera engines I've looked at. I have not been able to find a specification for chain length. That's something I would like to know. I have measured the length of 20 links on several chains with 65Kmi, 115Kmi, and one of unknown mileage. They were about the same length, within my ability to measure. I have not measured a new chain.

When you order the new chain, please measure the length between 20 links and compare to your old chain.

[proporsche]

PeteKz...
what i learned is this.You can see the position of the chain gear suport arm.How far does it extend..that will tell you if the chain is streched.
Or back in the days we looked at the bend of the chain ,clean the old one and compare the bend to the new chain.Holding it in the air not on table.
Ivan

I saved these two ,some genius welded extra space on the arms..the chain were streched and the arm on left was already hitting the chain housing.

[ant7]

From memory, I think that's the way I did the chain replacement on my first SC, at the same time I changed all the chain guides/ramps, and fitted Hydraulic tensioners too, years ago now.

Originally Posted by craig.wilson1

I'm sure there are some threads on the site addressing this, but my searches haven't turned up what I'm looking for.
I'm in the process of putting my 1979 911SC Engine back together. I didn't split the case and the engine is currently on the stand with only the P&Cs in place. Heads and Cam Boxes haven't been installed.

I'm sure I'm missing something, hoping for some advice.

[mike sampsel]

Originally Posted by proporsche

PeteKz...
what i learned is this.You can see the position of the chain gear suport arm.How far does it extend..that will tell you if the chain is streched.

Ivan,

How many miles did you get out of your chains, Ivan? I'm think they are good for many miles.

Hope you have a great holiday season!

Mike

[proporsche]

Mike.since i did my engine in 2009 the chains inside were all good.But doing this engine before shipping it to Europe i put what ever spare part i had in my stash.Left the piston and cylinders .
Those chains are still have somewhere in a box ...the engine had cabout 350K when i did it. so now over 150 000k later now still all ok;-)
Ivan

[craig.wilson1]

John Walker had told me that my chains were probably fine (I should have listened...

I might be able to cancel the chains order, if not I'll just go ahead with replacement.

[john walker's workshop]

I'd rather have one piece chains than the link style.

[dannobee]

Originally Posted by john walker's workshop

I'd rather have one piece chains than the link style.

^^^^^THIS^^^^^

Occasionally you will hear of someone changing the oil on one of these cars and finding a tiny e-clip or u-shaped thingy on the drain plug magnet. You guessed it, it's the clip holding the chain master link together. Stick with the factory style chains.

[craig.wilson1]

I caught things in time to cancel the order for the timing chains. Thanks to all for the input and advice!

[PeteKz]

JW, Ivan, others: Something else that will indicate chain wear is the cam timing. As the chain wears and "stretches" the cam will become more retarded (no pun in intended). Given the lengths of the chain on the tension side of the sprockets, I would expect a small amount of wear to shift the cam timing noticeably.

Note: This is common on Mercedes OM617 and OM616 diesel engines, which I have owned, and checked the timing and retimed them. It's usually not significant until about 200Kmi., but Mercedes diesel owners tend to drive their cars a long time!

However, I have not noticed significant cam timing shift on my engine (but only 30K since a major rebuild), and I have not heard others complain about it, so that also would indicate the chains last a long time. Have you heard or observed cam timing changes in higher mileage engines?

[ant7]

Originally Posted by PeteKz

JW, Ivan, others: Something else that will indicate chain wear is the cam timing. As the chain wears and "stretches" the cam will become more retarded (no pun in intended). Given the lengths of the chain on the tension side of the sprockets, I would expect a small amount of wear to shift the cam timing noticeably.

Note: This is common on Mercedes OM617 and OM616 diesel engines, which I have owned, and checked the timing and retimed them. It's usually not significant until about 200Kmi., but Mercedes diesel owners tend to drive their cars a long time!

However, I have not noticed significant cam timing shift on my engine (but only 30K since a major rebuild), and I have not heard others complain about it, so that also would indicate the chains last a long time. Have you heard or observed cam timing changes in higher mileage engines?