engine and drivetrain Educate me on timing chain sprocket please...

[bnam]

My car's PO told me yesterday he had changed the double wide chain to a single chain when he rebuilt the engine. He gave me the original double wide sprocket and a smaller 3 rows sprocket.

What are the benefits if any of the single chain with the double chain? He was aiming for performance.

What will it take to change back?

I also need to replace the racing tensioner he had put on that now leaks oil.

THx,

Byas

[Preyupy]

The single row chain is just fine until you start running high lift cam and higher rate valve springs. The single row chain should give at least 75k miles with mild cams and springs, they use less HP and are half the rotational mass of the double row chains. If the tensioner is leaking just remove the cap behind the spring ( outside of the engine ahead of the #1 exhaust port) and install a new crush washer under the cap. If it has a "racing chain adjuster" just remove the lock nut without turning the screw and install a coper sealing washer under the lock nut.

To answer your question about changing to a double row chain you need to remove the entire front timing cover and using a puller remove the sprocket from the front of the crank, replace it with a double row sprocket, then put it all back together with a double row sprocket on the cam. This is a lot easier to do with the engine out of the car with the oil pan and cylinder head off. Otherwise you are going to have trouble getting the lower cover off and back on and get the gaskets to seal.

[c.d.iesel]

you might also need wider chain guide rails to go with the 2-row chain -

as well as new rails for the different chain wear pattern,

and because the old rails may be brittle toast

[TobyB]

The guides didn't change width- whether the wear pattern would matter,

meh, I wouldn't worry if they weren't badly worn. I've got some

originals that aren't particularly brittle.

Can't say that about the M42, though!

That said, leave the single. They ran for 150k in the E21 and E30

and didn't look that bad afterwards.

If you had the engine out for something else, well, THEN it might

be worth the effort.

t