To avoid lots of swearing and unnecessary damage, check the timing gears slide neatly onto their respective bosses. If tight, first check for any high spots in the gear bores and key-way slots. Clean out using with fine emery cloth, medium Wet 'n' Dry paper, or some such. Remove the Woodruff keys then dress the bosses using abrasive material as mentioned previously. Re-check fitment before re-fitting keys. Check the key-ways and keys too before re-fitting. Get rid of unwanted sticky-out bits on the keys that would inhibit a slide fit. Clean out the key-way and de-burr top edges. I always file a slight 'flat' across them to give plenty of clearance to the gear key slot. If the pulley is a slack fit on the key, turn it anticlockwise before nipping the bolt up. ALWAYS fit it like this. It's imperative to fit cam (and followers in the case of solid wall blocks) following manufacturers instructions precisely using a good quality cam lube.
Sit the block/crank/rods/pistons/front plate/cam and cam retaining plate assembly on something that will allow full rotation of the crank without fowling. The gearbox is ideal, but needs to be stabilised by wedging with a thin sliver of wood or some such. Fit the flywheel retaining bolt and washer to facilitate crank rotation. Use something reasonably long as a lever to turn the crank with - jerky motion is to be avoided for accurate settings.
For those confused about which end is which of an engine, the FRONT is the water pump end, thus number one piston is nearest the water pump. Worth remembering as most engines are like this.
When timing cams in, two terms are continually confused - ADVANCED and RETARDED. To explain/clarify her are these terms applied to a common manufacturer recommended 106 degree setting as an example.
ADVANCED cam timing means that the valve events are occurring BEFORE the recommended point. Your measurement will therefore compute a reading LESS than 106. Generally this increases bottom and mid range outputs, but losses a little peak output. To correct this the cam will need turning counter-clockwise (anti-clockwise).
RETARDED cam timing means valve events are occurring AFTER the recommended point. Hence measurements and computations will give a value MORE than 106. Generally this increases peak outputs, but will lose bottom and some mid range output. To correct this the cam will need turning clockwise.
In both the above, I have stated just the CAM needs turning. To achieve this offset keys will be needed where non-adjustable cam gear drives are used, available in one-degree increments from 1 to 9 degrees. Also the above conditions are exaggerated when applied to small-bore engines. Modern cams have become such a developed art that sticking to manufacturers recommendations is usually the best course unless intimate knowledge of the type of engine build exists. Otherwise it could be tears at bedtime!!
The reason for taking readings either side of full lift as depicted in the methods is to get a true full lift point. A certain amount of 'dwell' exists at the cam lobe peak, so is difficult to ascertain true maximum lift point. The points used could be anywhere between 0.020" to 0.003". The nearer ).003" the better as some cams have asymmetric lobes. These will cause inaccurate settings to be established if points further from 0.005" where used.
Two cam timing methods are explained - one where the customary DTI, etc. is available, the other for those without specialist equipment (mechanical method).
Relevant part numbers -
WKN505 to WKN505-9DEG - offset cam keys where the figure indicates the degree offset required.
Camshaft Timing using a dial indicator can also be outlined as follows:
Rotate crank so piston one is at the bore top (TDC). Fit timing gears 'dot-to-dot'. Set up DTI with stem resting on number one piston centre with a little preload. Rotate crank backwards slightly (anti-clockwise looking at the front), then gently forwards observing the DTI, watching where the needle stops before descending. This is TDC. Repeat this procedure, stopping when the needle reaches its zenith. Zero the dial scale, and repeat until satisfied the needle shows zero on the scale.
Fit the protractor to the crank using the pulley bolt. Tighten so that you can just move the protractor. Fashion a pointer from the wire, held to the block by a water pump bolt and pointing at the scale round the protractor perimeter. Move the protractor to align pointer and zero, nip the bolt up to hold firm. Go back and repeat the last paragraph to ensure pointer is at zero on the protractor when the DTI indicates TDC.
Not essential, but to be super-accurate, reset the DTI - piston at TDC - with around 0.300" pre-load showing. Rotate crank backwards until needle on DTI is free of the piston then rotate forward until needle shows 0.200" BTDC. Note the degree reading on the protractor then continue rotating crank until DTI shows 0.200" ATDC. Note the degree reading. They should be the same although obviously either side of zero (TDC). The actual figure isn't important. If not, move the pointer in the relevant direction to correct this. Re-check by doing the 0.200" BTDC and ATDC again. Do it until the readings show exactly the same.
Pop a push rod down onto number one inlet lobe - second push-rod hole along from front. On small-bore engines make sure you fit the cam follower first! Reposition the DTI on top of the push rod, again with a little pre-load. Rotate the crank forwards and observe the DTI. The needle will swing round a couple of times, slow down, then reach peak reading (maximum lift) before falling away again. Zero DTI at this peak point. Rotate crank backwards and forwards a couple of times slowly until happy that maximum lift is showing with the needle at zero.
Rotate crank backwards until the needle passes the 0.025” mark. Stop and rotate it forwards very slowly, stopping when the needle reaches the 0.005" mark. Note the reading of degrees indicated by the pointer on the protractor. Continue rotating the crank forwards until the needle zeros and returns to the 0.005” mark again. Note the new reading from the protractor. Add these two figures together, divide by two, the result being where your cam is timed in at.
The idea is to get this to where manufacturers recommend your particular cam be set to give optimum performance. If your reading differs, corrective measures will have to be taken. How this is done depends on your choice of cam drive.
Equipment required - one 0.500” minimum capacity DTI with magnetic stand, 360-degree protractor and a piece of reasonably thick gauge wire to use as a pointer.
DTI - Dial Test Indicator/dial gauge
Protractor - degree wheel
TDC - Top Dead Centre, when piston is at highest point in bore
BTDC - Before Top Dead Centre, before piston reaches highest point in bore
ATDC - After Top Dead Centre, after piston has reached highest point in bore.