That's cuz the cam is not on the compression stroke, lol. Just turn the crank 360 degrees and then it will be ....... assuming the cam is already installed approximately correctly........ lol. and now both lifters should be on the base circle.
The ground-in cam advance is just to make it easier to get to the correct advance position with less monkeying around.
Say;
you wanted to install your cam plus 6* advanced.
And say your zero-advance cam came in at 2* retarded.
You would then need an 6+2=8 degrees offset key/keyway.
But if the Cam company has already ground 4 degrees into the timing of it, and it now falls in a 2* advance, then you only need 6-2=4 degrees of advance, so a 4*offset key/keway will do it.
Why do you want to install your cam at a specific position, other than dot-to-dot?
>Well firstly, you don't know if the dots are correctly stamped. Which would mean that the cam-timing could be anything. What if the Dot is off even by just one tooth?
>Secondly, advancing a cam, generally helps the engine develop a bit more CCP (Cranking Cylinder Pressure) which usually allows the engine to be a lil snappier at lower rpms.
>Thirdly, retarding the cam a lil, usually extends the rpm a bit on the top-end before the power drops off.
> the working range of most generic cams is about 8 degrees advanced to 4 degrees retarded, which total 12 degrees. Your engine will run anywhere in that range, and run well. But it will run best at about 4* advanced.
If you are a racer, the top-end might be more important.
If you are a streeter, and your engine only has an Scr of 8/1, making 130ps CCP, well then the bottom-end might take precedence.
But for most applications, 4* should be fine.
The thing is this, if you don't measure it now, you'll never know where it fell in. And if the engine turns out to be a dog, you may not know why, until you actually do measure it.......... If you still don't measure it, you can tear your hair out trying to find the power that was just never there.
> How much power is lost if the advance is out a couple of degrees?
Zero power is lost, it is just moved.... as a percentage. If you lose 2% on the bottom, you're likely to get 2% over the nose. So 2% of say 160hp is 3.2hp. But 2% of 320hp is 6.4hp It's the same 2%, but applied to a different part of the Power-Curve.
> sometimes, a couple of degrees of advance could be worth a few rpm of stall.
>Say you slap it in dot-to-dot, and it comes in at just 2* advanced, and you leave it there. Then you put the rest of the engine together. On the roadtest, you find out that the bottom-end is very soft, but once she get up on the cam, she goes like a cat on fire. But yur a streeter, and rpm after 5000 is not really important to you. So you do your due-diligence with a Compression test and a LeakDown test.
You find out that the engine is leaking less than 2% so nuttin wrong with that. But the C-test shows just 135CCP. But you know that the cam is in at 2* so it's a no-brainer, you can pick up about 1.6psi per degree of advance, so advance it to 6*, and pick up the CCP to close to 4 x 1.6=6.4 total, plus the 135= 142psi, and now you got a "torque-monster". But you lost about 200rpm off the top, which you don't much care about cuz now she is still motoring along quite nicely al the way to 60/65 mph.
Is 6.4 psi worth it?
IDK about you, but to me, starting from 135, yes it sure is. If I had 165psi, another 6.4 would not be. In fact, 165psi may already be too high for iron heads and pump gas. In this case, I would give up 5 psi to reduce/eliminate any tendency for detonation.
> So the bottom line is this; in a perfect world, dot-to-dot would get you 4* advanced on your cam. Do you live in a perfect world? If yes then just slap it on and go.
I know that degreeing a cam can be a PITA for a newbe. But it it really is a necessary step. Even if for no other reason than providing a reference point for future changes.
Happy HotRodding
