27 replies to this topic

[cooperrodeo]

It's the "rotate cam in each direction" that worries me. I hope you are approaching the two 5 thou points by rotating the crank (not cam) in the same direction so that slack in the chain or anything else is not confusing the issue. I would go further out than 5 thou as the accuracy of the cam around its peak is not as good as down its flanks.

[scubaet]

Yes rotating by turning the crank.

Took everything off and started again.

This time I aligned the dots and took new readings.

Rotated cam in one direction, clockwise from front of engine.

With dots aligned:

5 thou each side of pushrod 2 TDC

113 + 128 = 241 / 2 = 120.5

40 thou each side of pushrod 2 TDC

100 + 141 = 241 / 2 = 120.5

With dots aligned that leaves me 17 degrees out from desired 103 degrees.

[R1minimagic]

Did you use the same technique to set TDC?

i.e. a few thou each side and then set TDC as the average?

[Cooperman]

Most cams will time in within an accuracy of around +/- 4 degrees which, on a standard cam, will not really be noticeable. However, I once found an error of 9 degrees retarded with a new 266 cam. I put this down to inaccurate machining of the new (budget?) duplex sprockets, but if it had just been set dot-to-dot and not checked it could be expected that some power would have been lost.
I do use offset woodruff keys when necessary and always measure the timing. The cam timing figure is stated for a reason and the nearest you can get to it the better.

[dklawson]

Put the sprockets on dot-to-dot.

Find #1 or #4 TDC using the method you used and position the degree wheel so "zero" lines up with your pointer.
Move the DTI over the pushrod for valve #2.
Turn the engine over clockwise (looking at the front) slowly until you find the "peak" using the DTI.
Turn the crank backwards about 10 degrees, then SLOWLY turn it clockwise until you are about 0.020" before the peak you measured with the DTI. Read the degree wheel and record the value.
Continue turning the crank clockwise slowly, stopping when the DTI shows 0.020" AFTER the peak. Again, read the degree wheel and record its value.

Take those two degree readings and average them to find the point of max lift. Compare that to the cam angle your cam specs say is best and determine the amount of correction/offset you need.

As Cooperrodeo said, offset keys are a bit expensive so you don't want to buy an assortment... just the one you need (check prices at both Seven and MM but don't forget to check Mini Spares as the keys can be sent in a bubble pack envelope). They are still much less expensive than adjustable pulleys.

[AndyMiniMad.]

This thread should be made into a sticky due to the great info that is posted...

If the timing gear is poorly manufactured and cams are ground incorrectly then we should all be making sure our cams are properly timed in....Mine is the RE 13 OT and was bang on 104.5 deg at dot to dot. maybe I was lucky.,

[scubaet]

Put the sprockets on dot-to-dot.

Find #1 or #4 TDC using the method you used and position the degree wheel so "zero" lines up with your pointer.
Move the DTI over the pushrod for valve #2.
Turn the engine over clockwise (looking at the front) slowly until you find the "peak" using the DTI.
Turn the crank backwards about 10 degrees, then SLOWLY turn it clockwise until you are about 0.020" before the peak you measured with the DTI. Read the degree wheel and record the value.
Continue turning the crank clockwise slowly, stopping when the DTI shows 0.020" AFTER the peak. Again, read the degree wheel and record its value.

Take those two degree readings and average them to find the point of max lift. Compare that to the cam angle your cam specs say is best and determine the amount of correction/offset you need.

Thank you dklawson, I reset it again and followed your instructions exactly.

I get 144 and 114 for average of 129

here is the information on the camshaft, is any of that useful to me?


Application
Sports ' R '

Power Band
1500-7000

Cam Lift(mm)
I 7.43 E 7.99

Valve Lift(mm)
I 9.14 E 9.84

Duration
I 270 Deg E 280 Deg

Timing
29/61 66/34

Full Lift
106 Deg

VC (mm)
0.40

LTDC
I 2.16mm

Required Parts
CF1 / VS2

[bmcecosse]

Why on earth does it lift the exhaust more than the inlet??? How odd.
In fact - I check my timing after installation by measuring the valve lift at TDC on overlap. And I've never found more than a couple of thou difference.......with the cam set dot to dot.............

[scubaet]

Ok guys are you ready for this? I was just given the solution from AC Dodd on the Specialists Mini Forum

Your protractor needs to be fitted to the crank, not the cam,

AC

Aaaarrrrggg!!! Thanks Dodd

Initial readings came back at a 104.5 degrees dot to dot. Will redo them later to make sure.

[bmcecosse]

Errrr - you actually had it on the cam ????

[ukcooper]

I love a happy ending

[jaydee]

Do people still use Offset woodruff keys?

here i am..

[dklawson]

Son of a ....

I looked at your pictures no less than three times and I never noticed. I was focusing on where the pointer was... not where the wheel was. DOH !