Camshaft Timing

(Difference between revisions)

Revision as of 20:13, 8 August 2011

Checking and adjusting the camshaft timing is an important part of a competition engine. You can also do the same for your street 1200 to ensure you are getting the expected performance.

Also see Camshaft Comparison

Overview

Find TDC

• One dial indicator on piston head
  • Through spark plug hole
  • or, directly if head is removed

NOTE: You can also use a piston stop to find TDC

Advance crankshaft (turn clockwise) until lifter comes up 0.050":

• Second dial indicator on pushrod, to measure cam lift
• Timing wheel to have 360 degree measurement

Note the degree at which 0.050 lift occurs

Continue turning and note maximum lift.

Check each lobe the same way to see if any lobes are worn.

Fine Adjustments

Advance or retard the camshaft using:

• slotted key
• or, adjustable cam pulley

Modified timing cover to suit adjustable cam gear

Retarding the cam moves the power band up in the RPM range

Advancing the cam lowers teh power band in the RPM range.

Of course using the right camshaft is even better, but this technique can be used to see the effects:

• fine tune the cam to the engine
• fine tune the cam/engine to each particular track
• cover up a mis-matched cam

Slotted cam pulley for adjustment

Measuring lift

Factory Specifications

See Camshaft Comparison for more details.

240/240 duration (A10 Datsun 1000)
248/248 duration (standard small bore)
248/256 duration (standard large bore)
256/256 duration (performance engines)
244/248 duration (Late USA emission)

248/248 as used by standard A12

248/248/14/54/12/56

Late-model

B310 Australia?

A14: 256/248
A12: 248/248