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Dialing in your cams for a twincam

Posted: 26 Nov 2005, 19:10
by Robbo
Here is an image that will explain how to time the cams for a twincam... I took my cams out and then, stupidly, realised there were no markings on them to say where they were meant to be, and since it has adjustable cam sprokets I couldn't line it up using the dowel pin as I didn't have one!


Posted: 27 Nov 2005, 03:01
by Poida
Just one important thing I should mention...

If you wish to use an image or document that has a copyright notice attached, please contact the owner and seek their permission to duplicate it.

Most times it will be granted but some owners would prefer that you link to their site rather then copying their property. I'm happy to use the link method just as I already do on my Workshop Manual.

You'll see a number of links there that are obviously not to my own pages. It means we get to access information that we may not otherwise have. I usually keep a copy of the same info in case the site just happens to disappear as well but I'd only use that in the event the original was no longer available.

I've contacted Denny and requested his permission to use the above image.

Posted: 28 Nov 2005, 12:30
by Coley
Gday guys, i'm the dohc_gemini bloke from the other forum. I set the cam timing up like this, the timing marks on the cam pulleys straight up and no1 cylinder on t.d.c. as the chain has no timing marks. The chain I have is probably a custom one as parts for the twin cam engines are near impossible to get. I have had the engine started and i've driven it, it wasn't running quite right but i think that was more an electrical problem or a problem on the carby's.

If it was the cam timing, if it is a tooth out how badly would it be running? Because when I was mucking around trying to get the cam timing set, if it was a tooth out, the position of the timing marks on the cam gears were noticeably out, they weren't at 12 o'clock, which was how i was told to set them up. That is how the old toyota 2TG's were set up anyway.

Posted: 28 Nov 2005, 23:37
by Robbo
I had my cam one tooth out on a G200Z once... it didn't even start... not too sure what might be the deal with the twincam

Posted: 29 Nov 2005, 01:32
by Poida
Smashed valves and pistons if you are unlucky!!

Don't try it at home. :wink:

Posted: 31 Oct 2006, 13:16
by Tassie ZZ/Z
Sure the distibutor wasn't out a tooth?

Posted: 02 Mar 2007, 03:55
by archangel62
My input would be - if you're not sure your cams are dialed in right, turn the engine over by hand first. If a valve hits a piston and you're turning it over by hand, it shouldn't do much damage (if any), and if the valves kiss you'd probably know about it before you screw anything up... As opposed to turning it over when it will just go crunch bang.

Not saying you can't damage it by turning it over by hand, but it's far less likely. I'm definitely going to be turning mine over with a big socket and breaker bar (gently though) a couple of times before I start it.

Thanks lots for this thread everyone - especially Robbo and Coley. I've been very worried about this for a long time, but at last, I know how to do it.

Posted: 02 Mar 2007, 13:41
by Poida
You can see by the drawing Denny provided, that an imaginary line down the centre of the two bottom gears that intersects the two timing marks is all you need to align the bottom gears. First step is to be sure they are aligned as you fit the lower chain.

Now fit the top chain while you keep the bottom one in the position as shown and the the top timing marks are both at 12 o'clock.

As always being careful, turn the engine over by hand to be sure nothing is out of place before trying to start it.