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Another cam timing thread
#802085 03/20/20 10:47 pm
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let me start out by saying that I am no expert and I will try to explain my situation to the best of my ability.

I have a triumph unit that I am trying to degree the cams in. I have printed out johns (thank you) instructions on how to degree your cams and read them over and over. Although I think I got it the numbers aren't making any sense. Im going to describe what ive done with some pictures and description.

My first step was to set my degree wheel using the piston stop method. that was not a problem.
my second step was to set up my dial indicator on the drive side. ( I set up 2 so I could bounce back and forth without tearing down)[Linked Image]
[Linked Image]

Third step set my crank to 45 degrees then rotate the intake clockwise to .20 and set the idler gear. heres where it gets odd. I have followed the the gear stack method john had described and this gear gets me the closest.I can set the opening timing at 45 degrees btc at about .21 which I don't think is terrible but when I rotate the crank to the closing position @ .20 it reads 74 degrees. Im under the impressin that it should read 67. Out of the 3 keyways that is the best one. if I rotate the crank to 67 the dial indicator reads .30.
Im not sure if im being too critical or not doing something right. my timing card is below.
I will apologize in advance for not sizing my pictures if they turn out too big. just don't know how. Thanks for any and all input.

fred
[Linked Image]


80 FLH
66 Triton
71 442
67 atlas
71 TR6R
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Re: Another cam timing thread
britcyclenut #802086 03/20/20 10:54 pm
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I wanted to include my notes for each keyway. I hope they don't only make sense to me lol

[Linked Image][Linked Image]


80 FLH
66 Triton
71 442
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71 TR6R
Re: Another cam timing thread
britcyclenut #802097 03/21/20 12:07 am
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Unless you know better, use the lobe centre settings advised, I would suggest.
Then see how it goes, and experiment from there.

Re: Another cam timing thread
britcyclenut #802100 03/21/20 12:48 am
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I'll give it a shot. Ill start wrapping my head around that procedure.I hope it goes a little smoother and not raise more questions.... my head already hurts lol


80 FLH
66 Triton
71 442
67 atlas
71 TR6R
Re: Another cam timing thread
koan58 #802103 03/21/20 1:24 am
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Originally Posted by koan58
Unless you know better, use the lobe centre settings advised, I would suggest.
Then see how it goes, and experiment from there.

Exactly, it's rare to be able to get the opening, closing, duration and lifts to exactly match the timing specs. For instance, your dial indicator stems don't look exactly parallel with your pushrods. That's going to skew your lift readings relative to cam position, but it will skew both the opening and closing readings by the same amount, so the lobe center measurement will not change. Looking at your measurements, your 1st keyway gives an opening of 47° (BTDC?) at .20 (0.020"?) lift and a closing of 74° (ABDC?) at the same lift for a LC of 103.5°, your 2nd keyway has a LC of 111.5° at .20 and your 3rd keyway has a LC of 107.25°. The intake LC spec is 101.5° so using keyway 1, you're intake cam is retarded 2°. That's pretty close, I'd live with it.

Eric


1971 T120RV (R.I.P.)
1973 T140V/TR7
1993 Ducati 900 SS
Re: Another cam timing thread
britcyclenut #802107 03/21/20 2:45 am
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Thanks Eric.

I want to get the indicators straighter but that's the best could do. I was wondering if that had something to do with the readings. I understand the center wont change under these conditions (thank you) I will have to do the math like you did to fully understand your post but reading it 5 times and it slowly sinking in..... it makes sense. This is my first go at cam timing..... I've got a huge handicap.

Tomorrow is a new day and I will be attacking this again.
Then onto the exhaust...... ugh

Fred


80 FLH
66 Triton
71 442
67 atlas
71 TR6R
Re: Another cam timing thread
britcyclenut #802120 03/21/20 5:17 am
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I do it a little different, however I’m used to BSA Cams, and unless you vary from the timing marks, there is only one time you have to do it for all 4 pushrods.

This also helps accuracy if you know your cam followers are of the correct radius and not different this or unevenly worn, the data sheet mentions both 1.25” and 0.75” this will give a massive difference in cam behaviour on the road and when finding your timing figures. The bigger the radius is the better it will breath at top end but you will loose more at bottom end and the midrange. when possible I like to have my followers re-ground to the required radius as denoted by the cam manufacturer.

Finding the correct crankshaft degree is not accurate at 0.020”, you can have a fair amount of crank movement before the dial gauge has moved. As you know your lobe centre angle this saves you working this out from the data sheet. Still you still need to be able to work it out... or use the web camshafts website (not web cams website... this is something different!)

Align your timing gears up at the standard markings, as others have said have your dial gauge needle following the same line as your pushrod. Move your crank in the forwards rotation until you get 0.050” then note your crank angle. At 0.050” lift the lifter speed is really fast and where at .020” you may be a few degrees where there could be a discrepancy, at 0.050” your down to fractions of a degree.
Note this crank angle. Along with BTDC/ATDC/BBDC/ABDC

Move the crank forward again until the engine has done its full cam rotation and the dial gauge is now at rest. Ensure that it still reads ZERO, rotate the crank backwards beyond 0.050” lift then rotate forward again until you achieve 0.050” if you don’t check the dial gauge at ZERO in between then you can not be sure that your crank is truely at that angle, a 0.050” shouldn’t move the dial gauge but at .300” it might. But also rare. Doing this setting whilst the crank is driving forward will remove any lash.

Do the same for all pushrods.

If you use the we camshafts website plot all the values found and it will quickly give you the LCA for the positions you have.

Or...


Valve open angle + 180 + valve closeting angle =x

X/2= y

y - the valve open angle = the LCA as measured from TDC (inlet) or BDC for exhaust

For example. Your inlet is

45 + 180 + 67 = 292

292/2= 146

146-45= 101

As long as this LCA matches up as others have said then your 0.020” opening values are irrelevant. However should you need to move your pinion position you have a better idea of how to verify your timing.

Doing it on all 4 pushrods initially verifies that your followers are ok, ie you know if both inlets and both exhausts give you the same values at 0.050”... if they DO, then you only need to do further timing checks off 1 inlet and 1 exhaust.

If they are way off get your followers re-ground.

HTH

Last edited by Allan Gill; 03/21/20 7:39 am. Reason: Updated info

Now let’s all have a beer beerchug

68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (undergoing restoration)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)

Re: Another cam timing thread
britcyclenut #802121 03/21/20 5:22 am
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Your #1 numbers look to be correct.

Just adjust the amount you use for the clearance and you will see that #1 is pretty good.

That is essentially the lobe center method.

Last edited by GeoffLLLL; 03/21/20 5:25 am.
Re: Another cam timing thread
britcyclenut #802224 03/22/20 12:11 am
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I've been at this a good part of the day... all good stuff.. I'll have a follow up tomorrow. I think I can drive a nail in this tonight thanks to all of the advice.
Thanks guys for taking time to help
Fred


80 FLH
66 Triton
71 442
67 atlas
71 TR6R
1 member likes this: Allan G
Re: Another cam timing thread
britcyclenut #802344 03/22/20 7:54 pm
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Ok I think I'm done.... or at least I hope so lol. After wrapping my head around LC it made alot more sense to me as how everything jives.
Again thank everyone for all your input. Here are my final numbers.
All degrees were noted at .20
Intake opening 43° btc
[Linked Image]
Intake closing 74° abc
[Linked Image]
Exhaust opening 73° bbc
[Linked Image]
Exhaust closing 45° atc
[Linked Image]


80 FLH
66 Triton
71 442
67 atlas
71 TR6R

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