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[Datsun 1200 encyclopedia]

Camshaft Timing

From Datsun 1200 Club

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Category: Valvetrain

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

Contents

Overview

Find TDC

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

3639.jpgAlbum click to view
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. Compare to the camshaft specification sheet that comes with your camshaft. Or to the factory specifications below.

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

Find TDC

  • Turn the crank pulley to line up the timing cover "0" with the crank pulley mark. This is TDC.

OR

  • Find true TDC using positive stopped piston

Use a 14mm piston stopᴳ $16 USD (or you can make one).
174_6103ddba1cda1.jpgPost click for topic

  1. pull all plugs so you can easily turn engine by hand
  2. Put engine in approximate TDC, then rotate a bit further
  3. thread in the Stop to the #1 spark plug hole. Then turn the shaft in until it stops on the piston
  4. rotate back (by hand) a bit to be sure then engine stops (hits the Piston Stop)
  5. Mark the pulley
  6. rotate the opposite way (almost a full turn) until engine stops again
  7. Mark the pulley

Halfway between the two marks is TDC

Fine Adjustments

Advance or retard the camshaft using:

  • offset key for cam pulley
  • or, adjustable cam pulley

Modified timing cover to suit adjustable cam gear
3640.jpg

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

Advancing the cam lowers the 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
3639.jpg

Measuring lift
9528.jpg

Factory Specifications

See Camshaft Comparison for more details.

240/240 duration (A10 Datsun 1000)
248/248 duration (standard small bore A12/A13)
256/248 duration (standard large bore A14/A15)
256/256 duration (performance engines GX/A12T/EGI)
248/244 duration (1981-1982 USA)

248/248 as used by standard A12
23656.jpg
248/248/14/54/12/56

Late-model
18422.jpg
248/244/14/50/12/56
248/248/14/54/12/56
248/244/14/50/12/56
256/248/14/54/20/56

B310 Australia?
6195.jpg
A14: 256/248
A12: 248/248

Aftermarket Specifications

210/199 Camtech "turbo" profile 600A68A-TURBO
246/239/14/52/4/55
921.jpg


228/228 Iskenderian D8-66
228/228/5/43/6/43
266/256/24/62/24/62
7518.jpg

274/271 JTS 104CB
212/212/-2/35/-5/37
14441.jpg

291/296 JTS 140-6
238/238/15/42/10/47
15607.jpg

Smiths Regrinds (Mace Engineering)
0.050 specs not listed
7041.jpg

Camtech Cams
618: 199/196 2000-6000 RPM
639: 210/210 2400-6400 RPM
621: 220/223 2600-6800 RPM
609: 231/235 3200-7200 RPM
608: 241/243 4000-7000 RPM
604: 250/253 4400-8200 RPM
23657.jpg

JUN Camshafts
68, 72, 74, 76, 80, 82
23658.jpg

74 Bprojects RACING CAMSHAFT 296-7.0

Usage: new-style A12
Duration: 74 (296)
Cam Lift: 7.0mm (0.276")
Cold Valve Clearance: 0.3mm (0.012")
Valve Timing Centerline: 103.5(Deg)
Wavy groove finish and Surface Coating
*TOMEI Ouality Control

Auckland Cams


grind #A057 Auckland Cams

Type: Fast Road 
IN Advertised duration: 280 degrees 
EX Advertised duration: 280 degrees 
IN Duration at .050": 233 degrees 
IN Duration at .050": 233 degrees 
IN Cam lift:.284" 
EX Cam lift .284" 
Lobe separation: 108.5 degrees 

This cam will have a lopey idle and is suitable for high performance street use and/or rally applications. Wide power band 2200-7000 rpm. Can be used with stock standard engine and will run well. For best results use with of 10.0 to 1 compression ratio, twin carbs and extractors.

Conversion

Japan to non-Japan duration

68 272
70 
72 288
74 296
76 304
80 320
82 328

Valve Lift

Each manufacturer specifies this differently. The spec is valve lift (at the valve) but the cam lobe lift is amplified by the rocker arm ratio less valve lash:

Nissan: 1.44 ratio, cam lift not specified
JTS: 1.5 ratio, but they also specify cam lift
Camtech: cam lift only specified
Isky: ~1.48 ratio

For example:

Nissan cam lobe in.: 1.426" std (wear limit: 1.4055")
Nissan cam lobe in.: 1.187" base circle
Nissan cam lift: ~0.239"
Nissan Lash: ~0.013"
Nissan ratio: 1.44
Nissan valve lift: 0.331"

Valve Lash

Aftermarket camshaft grinders recommend from 0.010" to 0.024" depending on the profile (standard lash is 0.013" warm/0.014" cold).

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This page has been accessed 17,040 times. This page was last modified 11:29, 30 July 2021. Content is available under Datsun 1200 Club.