4 replies to this topic

[Uncle Bobby B]

Hi all,

 

I am in the process of changing my timing chain from Simplex to Duplex. However once fitted, my dots won't line up, whereas on the simplex they do. Can someone tell me what is going on and how I fix it please, I would attach a picture but I can't get the 'uploader' to work. The dots are about 3 to 5mm out of line. 

 

Cheers

 

 

[timmy850]

You might be out by a tooth on the cam sprocket? Try removing the chain and sprockets and rotating the cam one notch so that they line up.

[wile e coyote]

As above - you're not too far out though it seems and some factory engines were a bit off regardless - but best method is to get yourself a 360 degree protractor, an old wire coathanger and a dti guage - coupled with an offset woodruff key you can get the cam timing absolutely spot on (plenty of vids on youtube how to do this) a bit fiddly with the engine in the car but perfectly possible.

 

I always advance the timing 2 degrees for a simplex and 1 for a duplex to account for stretch as the chain beds in..... so you may be perfectly fine...

[GraemeC]

Manufacturing tolerances - which have only got worse as time has gone on and more repro stuff is made.

This is why some standard engines seem better than others.

 

To make it optimal you will need to time it in properly and use an offset woodruff key or adjustable timing gear. 

Otherwise it will run, just could be better.

[Ethel]

Compare the simplex sprockets with the duplex by fitting one of each. It should identify if one is out, assuming the simplex were to spec.