Multi position crank sprocket for timing chain - when to use?

[fairlaniac]

I've never dealt with multi position timing chains. I've really only ever dealt with straight up. I have a 3 position on my 390 that I built in 2006. I installed it straight up with no knowledge of how to use the other positions. So per a recommendation I bought a Cloyes 9 position for the 427 stroker I'm building (4.26 x 4.25). So can someone explain how it is determined which if any other positions you use on a 9 position?

Thanks!

[GerryP]

Honestly, Doug, the multi keyways just allow you to experiment.  You will not know if advancing or retarding the cam has some affect on power until you do it.  It works much better on a dyno since teardown is not quite as painful.

A lot of builders say running + or - just means you need to do a better job of picking the cam.  Probably so, but a couple degrees one way or the other will give you some insight into where things need to be.

On one occasion, I considered retarding the cam because I wasn't seeing the RPM I had anticipated from that cam.  In the end, I didn't rock the cam and I just got a new cam.

This probably goes without saying, but if you affect all the cam timing events when you move the cam, so while your engine might like a later-closing intake, it might not enjoy the later opening exhaust.  So, what would be ideal there is to spread the lobes to delay intake closing and advance the exhaust opening.  Again, just moving the cam won't do that. 

It's hard to know that and it kind of makes the argument of why we pay experts a good bit of money to know these things and get our projects tuned.

[Joe-JDC]

A lot depends on how the camshaft was ground.  That will be determined by cam card, and degree check on two cylinders, typically #1 and #6 to determine LCA, ICL, ECL.  Then after you know those figures, and know where you want to install the camshaft, you make the change on the lower gear to get the desired installed position.  If you don't know what the engine needs, then you will have to experiment by advancing and retesting, and advancing again, and if it is going the wrong way, retard and retest.  That is why dyno time is worth its cost.  Anything else is just an educated guess by trial and error.  Joe-JDC

[machoneman]

Plug the gears in straight up position. Check how the cam specs then match up to your actual measurments. Advance/retard if not close to the cam card specs. As noted, run it and see how it performs as anything else is a guess. Usually, one will advance a cam or leave it straight up. Retarding a cam (from the specs) is a rare move usually reserved for top-end charges in a true racer. 

[My427stang]

I hate to be a broken record and internet police, your procedure is 100% correct but there is no "straight up" timing set or position on the gear.  One of my pet peeves, although I don't want to be "that guy" either, your advice was absolutely correct of course

There is zero, or advance and retard on a timing set.  The term "straight up" means that the cam has been installed with both intake and exhaust centerlines the same, if you looked at the cam lobes from from the front, the two lobes would be in an equal position and not leaning one way or the other (advance or retard).  In fact, if you wanted a cam that has 4 degrees advance to sit "straight up" , you'd have to use the 4 degree retarded position on the gear

In the end, when do you need it? When your cam doesn't end up where you want it.  Or, if you want to try to adjust cam timing later for tuning..... Easy thing is to buy it up front and adjust as soon as you degree, otherwise, you have to buy a second set or drill for an offset bushing, etc.  Normally, you shouldn't have to, but with tolerance stack and/or combos where you want to adjust cam centerline, it's there

Last thing, you asked how to use it....let's say you degree your cam and intake centerline is supposed to be at 106.  When you check it using the zero slot, it's at 108.  You advance it 2 degrees by using the +2 slot and recheck centerline, it should be on 106.

Now picking a centerline, different story, it is a combination of experience, art and math.  We all have our techniques and it varies on the build