Camshaft Lift

In this article you will learn about measuring and adjusting lift. This came from our friends at Summit Racing.

When someone refers to camshaft lift, they could be talking about 2 different things.

Valve Lift
When talking about camshafts and lift, people usually mean valve lift. This is
the distance the valve actually moves. It is also called “gross
lift.” All camshaft manufacturers list this value.

Cam Lift
This is the distance the cam lobe rises away from the base circle of the
camshaft. It is the distance the lifter will move. It is also called “lobe
lift.” Some camshaft manufacturers list this value.

How is it measured?

Lift can be measured using a Dial Indicator. You
will need to know the Rocker Arm (The rocker arm ratio is the relationship between the 2 halves of the rocker arm) Ratio to calculate. On most engines, valve
lift will be greater than the lobe lift.

The formulas are as follows:

Valve
Lift = Lobe Lift x Rocker Arm Ratio

Lobe
Lift = Valve Lift / Rocker Arm Ratio

Example
#1: A camshaft with 0.270 in. of lobe lift will have 0.432 in. of
valve lift with a 1.6 rocker ratio.

Valve Lift = 0.270 x 1.6 = 0.432 in.

Example
#2: A camshaft with 0.468 in. of valve lift with a 1.5 rocker ratio
has 0.312 in. of lobe lift.

Lobe Lift = 0.468 / 1.5 = 0.312 in.

Measuring
Lift with Solid Lifters
When calculating valve lift for a cam with Solid Lifters, it is important to account for Valve Lash.

Example
#3: A camshaft with solid lifters, listed at 0.630 in. of valve lift
and adjusted to 0.015 in. of lash, will only move the valve 0.615 in.

0.630 – 0.015 = 0.615 in.

How does
it affect performance?

Increasing valve lift allows more open space in the intake and
exhaust ports of the cylinder. Theoretically, this means more air and fuel can
be drawn in. More exhaust gases can be pushed out.

Are there other camshaft lift factors to consider?

• Clearance Issues: If the valve is pushed
  open too far, it can hit the top of the piston. This could cause
  significant damage.
• Cam Lobe Profile: To increase the height of
  the cam lobe, it must either be wider or have a steeper ramp.
• A wider lobe increases Duration.
  This has its own effects on performance.
  • A steeper
    ramp is desirable because it opens and closes the valve faster. However,
    too steep and the edge of the lifter can dig into the lobe.
  • Follow this link for more on Cam Lobe Profiles.
• Additional Upgrades Needed: To take
  full advantage of increased valve lift, the following systems should be
  upgraded:
  • Air and fuel
    delivery system
  • Ignition
    system
  • Exhaust
    system

I hope you found this useful, and if you did, go and check out this post on Camshaft Duration.

I would like you to check out the post Camshaft RPM Range. Also, you could be interested in a post I did called “What shock length will I need?“.