C. Lobe Separation Angle (LSA)


- LSA is defined as spread in camshaft degrees between the intake centerline and the exhaust centerline.

- Overlap is the number of crankshaft degrees that both the intake and exhaust valves are open as the cylinder transitions through the end of the exhaust stroke and into the intake stroke

- LSA is ground into the cam and cannot be changed without grinding a new cam

- Bigger duration cams will have more overlap then a smaller duration cam even if both are on the same LSA.

- The key to making overlap work is maximizing the power in the rpm band where you want it.

- Long overlap periods work best for high-rpm power. For the street, a long overlap period combined with long-duration profiles combine to kill low-speed torque

- Reducing overlap on a long-duration cam will often increase midrange torque at the expense of peak power, but if the average torque improves, that’s probably a change worth making.

- Many enthusiasts purchase a camshaft strictly on the basis of how it sounds. A cam with generous overlap creates that distinctive choppy idle that just sounds cool.

- While doing my research on the T1 I cam across this dyno in which if I recall Tony (Nineball) stated that the blue graph was a T1 (112 lsa) and the other 2 where a B1 (114) lsa. 112 vs. 114

- What really affects where the cam makes the most power is the intake timing events. What affects drivability most is the exhaust-closing event.


D. Advance and Retard:

- When you see cams specs like 224/224 .563/.563 112+4; the +4 denotes that the cam has 4 degrees of advance ground in.

- Most off the shelf cams have 2 or 4 degrees of advance ground in. This lowers the power band slightly and offers more low end and midrange at the sacrifice of a bit more top end power

- For cams used primarily on the street the advance is best appreciated. For a strip or racing setup 2 or 0 degrees advance will net you more peak power in the upper ranges of the power band

- To find out if you cam has advance ground in you can check on the cam card. Besides the +2, +4, you can determine the number by looking at the intake center line (ICL). Referring back to the T1 cam card you’ll see that it states that those are the specs when installed on a 108 ICL.

- Subtracting the ICL from the LSA will give you the advance: 112 – 108 = 4 using the T1. Or 113 – 109 = 4 using the G5X2.

- Retarding the cam does the opposite of advancing it, it pushes the power band up slightly and gives more top end power.

- With an adjustable timing chain or degreeing the cam you can install the cam at different ICL’s.

- Keep in mind as stated; most cams already have advance ground into them so if you buy an adjustable timing chain and advance 2 degrees you’ll increase the overall advance to 6 degree’s if the cam has 4 degree’s ground in.

- Also with big cams and/or milled heads piston to valve clearances starts becoming an issue. If in doubt always clay the heads and find out your PtV clearance before installing/advancing especially if your cam has a big intake duration as advancing starts the intake valve events sooner.

- Degreeing or installing dot to dot at the said ICL is the best bet.