Like the title says, adjustable cam gears for Z31 motor. I used them once to check some cam timing on the dyno, got my information then set them aside. Time to see them do their trick for someone else. FWIW, on a non-turbo motor making adjustments with these and timing picked up roughly 10hp (peak).

Located in NH, 03301, shipping on the buyer

 

Wow, I am impressed. 10hp is a big deal. I would like to know more about how to use these... I'm guessing it has to happen at a timing belt change (makes sense). And how does this differ from advancing/retarding the regular timing adjuster on a Z31? Is there an advantage to using these that you can't get from any other timing set up/adjustment?

Thanks in advance for answering my Qs!

 

It was on a road racing car, NA motor that had some work done to it, headers, open exhaust (no cat, minimal muffler). I don't remember where we started, nor where we finished but it was a function of first adding advance to the timing, then retarding the valve timing. I think the timing increments were in the 3-5 degree range and the valve timing was at 2 degree increments. You then need to go back and re-adjust the ignition timing. It took several pulls to get it right. We were working in the range of 170hp at the wheels, so yes, 10hp was a big deal.

You can put these on at any time, but you will need access to the idler so you can slacken the belt, change the gears, reset the belt.

Ignition timing & cam timing are different animals entirely. The changes these make affects the ignition timing since the distributor is driven off the LH cam. However, you can simply return the ignition timing to where it had been once you have adjusted the cams, the distributor adjustment has a lot of range.

Cam timing has a bigger impact on performance than ignition timing, but in general, most cars have pretty close to optimum timing from the factory. Cam timing changes the dynamic compression ratio and can change where in the RPM range the motor makes its peak power, and can have an effect on the total area under the curve.

I used these just to verify what the cam timing should be so I could then get a different motor set up properly. The class I was racing in did not allow the use of adjustable cam gears, but it did allow other options for resetting cam timing, so I simply needed to know where the timing should be, then build the motor accordingly.

 

Cool. I think I get it. Tell me, when you are adjusting the cams, that would set your ignition timing off, yes? - so, using your timing light, you readjust the ignition timing. Or, was there another test you were also doing - like compression? At some point, you had to know you were getting your extra HP from the right combination of adjustments...SO, how did you know you found that point? Thanks again!

 

It was all done on the dyno. 3 or 4 pulls to start to insure we had repeatable data. Then start advancing the timing until the HP starts to drop off, then set it at the point where it made the best power.

Start retarding the cam timing, but each time you do this you need to reset the ignition timing to the point that had been selected prior to messing w/ cams. Again, you keep making adjustments until the power starts to drop off, then back up to where you'd found the best pull.

Now you need to repeat the ignition timing changes to confirm that w/ the new cam timing, the ignition timing is still correct as it may not be the same w/ altered cam timing.

At least an hour of time on the dyno.

Let me know if you're interested, we can work out how some arrangements.

Thanks
Matt

 

So, without a dynamometer, you would just be guessing at the adjustments? You need the dyno to do it with accuracy. Correct? Thanks.

 

Price?