F40LM

I have ordered a set of offset cam keys from 928 motor sports. The 928 uses 2, I only need one for my '86 944. The set cost me $43. Will sell the extra one I will get for $21, shipped in the lower 48 states. Josh has had some great results with this mod, check out the write up on the NA-tune thread. PM me if interested.

Michael

V2Rocket

I'm guessing if you want to advance/retard timing you just flip the key around?

F40LM

Yep. This can advance or retard timing 4 degrees. They arrived today will post a pic soon or you can take a look on the 928 Motorsports web page.

MAGK944

Never used these offset cams so...
How do you know 4* advance/retard is optimal for the tune?
What if you need 2* or 6*?

Excuse my ignorance but I've only used the adjustable type of cam gear where you can advance in infinite steps until its were you need it. It seems like this offset key is an easy way to maybe get back to stock after a cylinder head resurfacing but not for fine tuning purposes. Please correct me if I'm wrong.

Butters944

How would this effect a bone stock car..?

F40LM

Item has sold.

Rick Ryhal

Paypal sent

Thanks

Jamesr6967

* Read the write up by Rogue (Josh), he talks about it . (A few days ago, maybe a week or two?)

Rogue_Ant

The typical kit comes with a 2° and 4° key, so that you have some adjust-ability. Having either key, you could use it to advance/retard and in-conjunction with changing the cam 1 tooth (a 9° change), it gives you quite a few options:

+2°
-2°
+4°
-4°
+5° (+cam tooth, -4°key)
-5° (-cam tooth, +4°key)
+7° (+cam tooth, -2°key)
-7° (-cam tooth, +2°key)

Yes, this is not the fine-tune capability that an adjustable cam-gear gives you, but it gives you the majority of the gain for ~1/10th the cost. You just need to test which combination is best, and fortuneally I did that already

On a car with a non-milled head, and stock-camshaft, 4° advance is what I suggest, as that is going to bring hp&tq on earlier, and make better use of the camshaft.

See my post here:

https://rennlist.com/forums/9898601-post278.html

Butters, I would expect a 5-6% increase in power at pretty much every RPM. The difference will taper-off in the higher (>5500rpm), but for the majority of the RPMs, it will make a very noticeable difference.

F40LM

Yep it's yours. Thanks Rick. Will go in the mail Monday.

Michael

MAGK944

That is quite a range of adjustment for something that costs under $50. Thanks for doing the calcs, learn something new every day here.

V2Rocket

Josh, could you explain why there isn't much power gain at higher RPM when retarding the cam? One would think, that shifting the powerband up in RPM, more power would be produced as HP is a function of RPM...

blown 944

Spencer,

I'll answer as I explained it a little to Josh when on the dyno.

When you build torque earlier in the rpms it compounds apon itself to a degree and thus adds horsepower too.

When shifting the torque curve to the right ,there isn't enough RPM or airflow to take advantage.

My thoughts on it

Rogue_Ant

Agreed. Additionally, even though retarding the cam did help keep top-end power up (though it was still less peak hp than advancing it), the stock cam (and maybe intake manifold?) is simply not aggressive enough to make use of the upper-RPMs.
Changing cam-phase does not affect total duration or lift, so while phasing the cam shifts the power around, it is still ultimately limited by the actual cam-profile.

Here is an overlay, the only difference in the two pulls is cam-timing (retarded 4° vs advanced 4°, other mods were my NA-Tune & 2.5" exhaust). The blue is the retarded cam, the green is the advanced cam - everything else is the same. Which curve would you want?

V2Rocket

Damn...looking at those numbers, again assuming 15% loss, compared to factory published crank figures (143HP/137TQ) those are big gains, across the board...about +13HP/+30TQ!