Cam Shaft Degree

[Snakebit]

My engine builder installed my cam shaft. The cam card called for 106 degrees. He installed the cam at 105 degrees at 2 degrees advanced (multi keyed crank sprocket). So if I set my timing for 12 degrees advance, what do I really have???

[blykins]

You're confusing cam timing with ignition timing.

Cam timing is the relation of the valve events to the crankshaft position. If he set it at 2 degrees advanced, then the LSA was 107 and he put the ICL at 105.

Ignition timing is where the plugs fire in relation to the piston position. If you set the initial timing at 12 ° BTDC, then the plugs are going to fire at 12 degrees before TDC until the distributor advances the timing. If your distributor has 20 degrees of mechanical advance (for example), then your total timing is 32 degrees.

[patrickt]

Originally Posted by blykins

Cam timing is the relation of the valve events to the crankshaft position. If he set it at 2 degrees advanced, then the LSA was 107 and he put the ICL at 105.

That's not gonna make a lick of sense to him. Snakebit, here's a graph of my cam. Seeing a cam's specs displayed this way will help you visualize what an "intake center line" (also called "intake center angle" or ICA) is and what "lobe separation angle" (also called "lobe center angle" or LCA) means along with some of the other stuff that's important to a cam, like duration, lift, overlap, and what not. You can see that my cam is installed with six degrees of advance (LCA-ICA). If you tell me the maker and model number of your cam I'll do the same with yours and graph it as installed with two degrees of advance.

[blykins]

Those curves would be prettier if it was a roller cam.

[patrickt]

Originally Posted by blykins

Those curves would be prettier if it was a roller cam.

Yeah, but who wants to be fishin' needle bearings out of their FE?

[blykins]

I'll save everyone the drama and won't go there.

[blykins]

Hey Patrick, you're on the FE forum, right?

[patrickt]

Originally Posted by blykins

Hey Patrick, you're on the FE forum, right?

Yes, as patrickt_FE.

[blykins]

I'm going to PM you...

[351cuin]

Old school trick to wake up low end torque...advance cam two degrees. Been doing it for years. Crank Timing marks will change by two degrees. So to set your timing to 12 degrees use the 14 degree mark. I beleive this is what you were wandering.

[Jac Mac]

Originally Posted by 351cuin

Old school trick to wake up low end torque...advance cam two degrees. Been doing it for years. Crank Timing marks will change by two degrees. So to set your timing to 12 degrees use the 14 degree mark. I beleive this is what you were wandering.

With multi key sprocket Ign timing marks wont have to be altered, that only happens if you use an offset key on the crankshaft.

[Snakebit]

Thanks for the help and the humor. So the bottom line is 12 degrees is 12 degrees.

[Excaliber]

I had to fish those needle bearings out of my FE, ONCE, flat tappet now.

[Keithc8]

TDC is always the same no matter where you put the camshaft and the camshaft is installed in relationship to TDC so your timing is not affected by degreeing the camshaft. Your timing will be what it is if the damper has been checked for TDC with a stop and a pointer. I have had guys put there timing light on 35 degrees and time there engines on 35 degrees for a total of 70 degrees and mess up their engine but that is another story. Also just because you use the 2 advance slot on the timing set does not mean that the camshaft is in 2 degrees advanced. It could be advanced more or less than that. I get a lot of my camshafts with 4 degrees advance ground into them which makes it easier for me to degree. I normally start with the camshaft in the straight up position. Good luck, Keith