Adjustable cam sprocket timing

mikey · Post by **mikey** » Wed Aug 03, 2011 9:41 am

I've just realized that I know nothing about engines and that my cam timing will be out now that the head has been skimmed.

So I figured I'll need to check the timing at least, which wouldn't normally be an issue since stock cam sprockets have 4 different timing marks to choose from. But mine are adjustable, and you can't see the normal timing marks which should be visible through the spokes.

How the frig to you time these?

Baker93 · Post by **Baker93** » Wed Aug 03, 2011 6:04 pm

Oh God this could fill a book.
First thing you need to know is what cam has the thing got in it ! and what timing ie valve opening and closing does it (the engine want/need).
If it is standard can someone (Mike Lucas) help out and let us know what the standard cam values are.
If it is not standard you can measure it yourself, but explaining this will fill another book. Check the back of the cam to see if there are any markings we may be able to identify it. I will look through the records i have to see if we have ever measured or dailed in a standard cam.
Anthony

mikey · Post by **mikey** » Wed Aug 03, 2011 6:11 pm

It's got "JAPAN" cast into it I think which if I'm not mistaken means it's stock. But I don't know if it's had a grind.

Can I simply put it back together the way I took it apart and then see how it goes, if the torque has shifted along the rev range look at adjusting it?

mikey · Post by **mikey** » Wed Aug 03, 2011 7:30 pm

This how-to mostly makes sense to me. I guess I should do this?

Baker93 · Post by **Baker93** » Wed Aug 03, 2011 9:23 pm

Hi
Yep that pretty much sums it up. A degree wheel and dial gauge are musts to do this accurately as is a good Pointer. The key here is to have accurate and repeatable measurements. This will not be a 5 minute job and adjusting the cam will drive you nuts. I generally try to achieve accuracy of 1/2 a cam degree. Remember when taking figures from crank degree wheel they are twice thecam degree change. ie 2 crank degrees is 1 cam Degree.
If the cam is standard this job will be a little easier as (if memory serves me correctly, someone please correct me if im wrong) the standard cam is symmetrical. Set the cam at as close to 6 Crank shaft degrees advanced and go from there.
Note. Always check piston to valve clearances @ 5, 10 & 15 degrees before and after TDC before running motor. You should have a min of 120 Thou on exhaust and 100 Thou on inlet. If you have not something is wrong.
Another easy way would be to borrow a standard cam gear. and set up the motor on it then change back to the adjustable wheel for fine tuning if need be.
I have spare cam sprockets you can borrow if you wish.

Have Fun
Anthony

mikey · Post by **mikey** » Wed Aug 03, 2011 9:46 pm

Thanks Anthony, I've been doing a little reading and it's starting to gel. I'll pick up a degree wheel tomorrow (and the head) and do it over the course of a few nights and take my time.

I'll report back with progress (and no doubt, stupid questions!)

mikey · Post by **mikey** » Fri Aug 05, 2011 7:04 pm

Right, I've got everything together and with some luck I should get everything buttoned up this weekend, which'll be awesome.

Just wondering if I should be aiming for zeroing my cam timing or if there's any performance benefit in advancing it at all with a (presumably) stock cam.

I'll be confirming my cam is in fact stock while I'm at it.

mikey · Post by **mikey** » Mon Aug 08, 2011 1:55 pm

Baker93 wrote:Set the cam at as close to 6 Crank shaft degrees advanced and go from there.

I just re-read your reply and noticed this. I've set mine up at intake lobe center of 108 degrees which is what I think is stock. But given what you said here, should I be aiming for 102 degrees instead?

Thanks, Mikey.