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Camshaft degree measurement

2K views 3 replies 3 participants last post by  pistoncams 
#1 ·
Hi, I am trying to figure out how to measure the duration of camshafts.. SOHC set up. I have a head set up (on the bench) to measure valve movement with the degree wheel attached to the camshaft. It measures lift accurately but I don't know how to read the degree's to figure duration. This wheel was designed for crankshaft measuring, how would I adjust for camshaft instead?

Exhaust at .050 lift: open at 64 degrees, closed at 189 degrees
Intake at .050 lift: open at 177 degrees, closed at 299 degrees

thanks
 
#2 ·
I have never seen a need to check the cam timing [other than stock timing marks] because if it is off, there is nothing you really can do about it. With race engines, you can 'dial' it in, but not with a cam gear locked by a keyway.

That said, I do not believe you can check the cam timing since the head is off the block. Your measuring when the cam opens/closes by the crankshaft degrees. Take away the crankshaft like you are doing and you get half the equation.
 
#3 ·
checking degrees

I am old, 68. I used to degree cams on Chevy and Pontiac v8 engines. It was done with crank, cam, timing chain and degree wheel, installed in block. You put offset key in cam to change degrees. A real time consumer till you got right key. Keys only adjusted cam -3* to +3*.

Old V8s to new VWs you would need a few machine shop tools to measure valve movement. But why do it, you cannot change lift or duration anyway? You can only measure it. Cam should come with fact and setup sheet with all the info.

Now with over head cams it is much easier. That is why adjustable cam degree gear was invented, a build in mini degree wheel. They usually adjust between -8* to +8* and cam be done in minutes at the drag strip or side of road. The two engines I have had them on are 8V and 16V. They help a lot in performance. The two ways to know you got it dialed in right, seat of pants driving and best way is drag strip times.

Hope I did not bore you, pistoncams
 
#4 ·
look up

Cams turn two times to every one turn of crank, you probably know that.

Draw out with two circle, one smaller inside the larger. Mark where intake opens at correct degree on circle. Draw, say red pen, to degree of intake closing on circle. On other circle, do same with exhaust. Draw straight lines from center of circle to the 4 marks. Now do the math + or - the two over lap exhaust stays open a while to let incoming air/gas to help push out exhaust and get incoming air/gas moving faster to draw in. Talking NA engines, not turbo or super chargers, their cams are setup somewhat different.

To measure lift, if you have stock cam, measure heal to peak with mic. Then do same with new cam. Subtract stock from new cam will give additional lift. You need to know lift of stock cam which easy to find, add additional lift.

In real life, most cams from cylinder to cylinder are not exacted. They will be off a little degrees.

It is hard to write this out, hope it makes sense?
 
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