Topic: How to properly degree a cam

[Justind97]

Hi Everyone,

I'm in the last stages of building my motor.  I have a WebCam 358a grind cam with adjustable cam sprocket.   This is my first time doing this so I want to make sure that I do it properly.

The below information is a sheet that WebCam sends with their cams.

Valve Timing Information
Engine: Cb500 / 550 71-78 8V
Grind # 358a

Degree Cams in on LC method

               Intake      Exhaust
Valve Lash           .004”      .004”
Valve Lift             0.330      0.330
Duration               280*      280*
Duration @ 0.050   228*      228*
Lobe Center      107*      107*

Intake opens   7*   Before TDC   Exhaust Opens 41* Before BDC
Intake closes    41*    After BDC           Exhaust Closes 7* After TDC

Valve timing is checked with zero valve lash @ 0.050 inches of valve lift.


Here is what I have done.   Installed the cam and the sprocket. Brought Cylinder 1 & 4 to TDC.   Aligned the cam slot to be parallel to the valve cover surface.  Snugged the cam sprocket down.

I took a donor cover and sliced off the big hump for the cam sprocket, so now when mounted, I have access to the cam bolts. 

Set my degree wheel on the crank.

Set my lash on the cam to .004" I/E as mentioned in the table above.

Set my dial gauge on the end of the valve.   Measured my lifts, and degrees to make sure they correlate with the paper.

My question is the last line in bold. Valve timing is checked with zero valve lash @ 0.050 inches of valve lift.  What does this mean?   is the Zero valve lash because the valve comes under load, therefore no lash?   

Thanks in advance!

[TurboD]

Yes check with zero lash. At .050 lift the intake should open at the 7* number.

This means that instead if setting the valves at .004 lash for operation, you would want to set them at zero for checking.

[Justind97]

Yes check with zero lash. At .050 lift the intake should open at the 7* number.

This means that instead if setting the valves at .004 lash for operation, you would want to set them at zero for checking.

Thank you sir!

[Bill/BentON Racing]

And dat's very important,  some check at .040, and some at running clearance, Bill

[TurboD]

Bill is correct. There are a number of ways that you can use to degree a cam in, they all will end with the same result. To not confuse, go with the instructions, this is pretty much the standard for checking these days.

[madmtnmotors]

Lift is measure at the valve (either tip of valve or top of valve spring retainer), with a dial gauge, correct?

[TurboD]

Lift is measure at the valve (either tip of valve or top of valve spring retainer), with a dial gauge, correct?

Yes.

[MRieck]

Lift is measure at the valve (either tip of valve or top of valve spring retainer), with a dial gauge, correct?

Yes Wilbur....off the retainer or the bucket. It can be a real #$%* on tight, small valve engines too.
 Not to confuse anybody but I like to check the timing at the running lash i.e. .005, .006 etc. That way I get the numbers as they exist (or close to as internal combustion engines are not exact with stuff bending and flailing etc)  when the engine running. All you do is subtract the lash from the opening and closing #'s. if the cam is supposed to open the valve @30 it will do it at 25 with .005 lash. It will close the valve earlier than the advertised # too. Be aware that is is generally impossible to hit the opening/closing #'s on the cam card.
 Like Turbo said different ways off doing it....the most important in all of them is to get true TDC.

[TurboD]

Yes getting the degree wheel set to TDC is very important, all of your readings rely on it.

Like Mike I have a number of ways that I use at times, The reason I did not discuss or recommend them is, for Justin to get the exact numbers (open and closing) stated on his cam card the lash needs to be set at zero.

These old Honda's are a breeze to check, a new Hayabusa not so much. a real pain. Lol

[PeWe]

I time my cams at 0.04" lift when many other cams I compare the data with are specified at that lift.
To measure the correct data must be with running lash. Min lash to get max lift and duration. 0.1mm IN, 0.15mm EX when I have metric blades. Less lash too tight, right? Tune cams.

I'll test with std cam sprocket next time (not adj one). Check when cam open/close and grind exact that much needed to get correct values. The sprockets with oval holes have so wide holes, like 2 cogs. The bolts have never came loose, yet.

I use APE TDC tool  http://ape-store.com/shopsite/page15.html  update the case mark vs T on adv
I used it mostly to be sure about the ignition timing, F vs case mark. If the cam will be 2 degrees wrong in either direction, no problem for me as long I do not move the wheel during the timing of the cam.

Ignition is more important to get it right, to be sure about no pinging that can be difficult to hear in higher speeds. I have 2 old pistons as reminders. Hole and almost hole

[Fastbike]

I don't care where the lash is set, it still works out right.  I have checked at .006, .040, .050.  I set my cam centerline at .050 because it is easy to remember and it has gone past the opening ramps by then for a more accurate reading.  I usually triple check my final settings to be sure of the readings.  It runs OK.  Hell, it's only bracket racing .  Oh, and I have TWO camshafts to time!!

[TurboD]

Yes you can check at .006, .020, .040, .050 etc and with or without lash to find the lobe centerline, on occasion I will check .050 or .100 on each side of the total lobe lift. BUT to get his opening and closing numbers on his cam card, he needs to check at .050 and with zero lash..

[Fastbike]

Turbo,

Don't take my ramblings too serious.  Ask Bill Benton or Jim French.  Or even Sam Green!!

[dragracer]

Yeah, big fun with a DOHC motor. I set mine at the running clearance using .050. Try calculating overlap with two cams, makes you appreciate the fact the cam manufacturers took care of that little fact on a Sohc . Like someone else said, the very most important part of cam degreeing is finding TDC and never altering the pointer after that. In reality, degreeing a cam is just moving the power around anyway.

[TurboD]

Oh I'm not. Cam timing can be very confusing at times, yes there are a number of ways to check it. I was just trying to keep it simple for him so that he would get the numbers on his card.

I personally look at cam cards and suggested settings as merely a starting point or base line anyway.  When I built racing Briggs for gokarts, we had lash settings all over the place, I even had fixtures to twist the cams to change centerlines.

[PeWe]

There are tons of cam degreeing instructions on this forum.
For CB750: http://forums.sohc4.net/index.php/topic,98137.0.html
You can find information on car forums too. Old V8's use one cam too.
This article is interesting and describe the importance of IN closing.
http://www.hotrod.com/how-to/engine/ccrp-9812-secrets-of-camshaft-power/

I change and time cam with engine in frame. I do not know if CB500/550 can do that or be modified with frame kit as CB750.
The degree wheel is very small, not as the big ones the experts here use for total control. Small wheel OK for me, maybe 1 degree off.
On the photo below degree wheel with Dyna-S still mounted. I have now points, the entire point plate need to be off hanging in its cable. The points will touch the wheel otherwise.

Note! No plugs in when turning crank with the week ign nut/shaft. It can cause more play to the advancer when that one turn the crank around with its pin into the end of the crank. I guess that's why my advancer has 2-3 degrees in total play and setting the true TDC is a vital part of the procedure. I think Í get correct TDC with advancer unit turned max counterclockwise of its play. With this setting it can move when turning the crank during the timing. I have turned crank with kickstarter to avoid that the advancer moves.

Not only cam timing, set the advancer correct is a part of it too so you can trust the T, F and full advance marks ' '. I check true TDC before mounting the rocker arms so the valves will not move and ev collide with piston stop. Maybe safe anyway. I have larger in valves 34mm, std is 32mm

Guys with Dyna 2000 do not use the advancer.

EDIT: Action Fours cam timing docs I got with my AF cam added.