Mike S

So while I was pulling my car apart to replace the head gasket last night, I noticed that the camshaft timing mark was off by one tooth. When the motor was at TDC, the mark on the cam sprocket was one tooth back of the mark on the housing. Is there an advantage to retarding the cam timing? Should I align it back up to the way it should be when I reassemble it? How much retard is this...5 degrees?

Jeremy Martin

yes; you can gain performance by retarding the timing, but 1 full tooth is way too much to gain performance.

James86-951

Retarding the timing gives you top end power and advancing the timing gives you bottom end power. When in doubt, especially with the cam/crank timing, set it to 0!

Van

Has anyone ever done any dyno comparisons to see if there is a high-end performance gain for retarding the cam timing by a tooth (or a partial tooth)?

(One tooth is 9 degrees on the cam shaft.)

Duke

+/- 1 degree altered my power output by almost 10% at the same boost level so small changes can do very much. I would definately recommend doing the adjustments on the dyno, it's hard to notice the effect on the street/track.

Van

Wow, that's great! I was looking at offset keys at the site of the guy working on the 968 supercharger.

theedge

Why not get an adjustable cam gear? As long as you get one of the good ones that adjusts from the front, its pretty easy to dial things in.

JohnKoaWood

OR get a 16V head with 2 adjustable gears!

CPR

^^^^^^crazy bastard

Duke

Also, my experience isn't that adjusting the cam gear just moves the powerband up/down. It can actually bring more power to the table without losses in another region.
Look at this dynochart. This is cam gear adjustments ONLY!

333pg333

So what do the colours correspond to Duke? Which lines are more and which are less cam timing?

Duke

In this case blue was at 0, red 1 deg retarded and green 1 deg advanced.
But it can be different on different engines depending on how much the head has been resurfaced etc.
As you can see, it really starts to make a difference after 6000 rpm.

DLS

is red 1 deg retarded correct??

Duke

Yes.
Remember that this is pretty modified engine so you don't get the same results as on a stock engine.
This is with a very large turbo and it spooled over 500 rpm later on the Rototest than on the street. With a small turbo that spooled at 3000 rpm and more stock stuff the curves would have looked differently.
That engine setup is for top end power so a retarded cam does not yield the same results as on a stock midrange engine.

It really is a system that's why is so important to do a custom tune and setup for modified engines to be sure you get the most out of it.

Oddjob

+/- 1 deg. of the actual cam shaft? Or is that the cam relative to the crank shaft angle? Meaning 1 deg crank is actually 0.5 deg on the cam.

I would assume actual cam, but I have seen people reference cam timing relative to crank angle, so just wanted to confirm.

Thanks,