Degreeing a cam with asymmetrical lobes

What is the best method to use to degree a cam with asymmetrical lobes?

Maybe I'm not understanding the question, wouldn't matching the valve events @.050 still work?

Follow the mfgs recommendations. You'll get different centerlines depending on where you measure so just follow the instructions. They might tell you to use an 0.050 lift number, or perhaps they'll tell you to use something else. They should know how they want it installed.

BTW - this question sparked a huge debate on the old SpeedTalk board that went on for months. Mike Jones kept telling everyone to shut up and to just follow the mfg instructions but people kept arguing about where the center line is on a non-symmetrical lobe.

Usually take the readings .050 before and after max lift

Use the cam card numbers, all of them of @ .050. then you will know what you have, and if your measurements vary at all.

I asked this question here about 20 years ago when I tried my first street roller which was visibly
very asymmetric just eyeballing it....the answer was do centerline method the same as anything else.

I predict the answer will be the same, and might even come from the same people as back then.

As a sanity check you can work the numbers both @.050 and @.020 before and after max lift to see if it comes out the same.

the safest way is the centerline method, but that doesn't mean the .050" thing won't work. this is time consuming but when i mess with asymmetrical lobes i check seat timing to find out how long the closing ramp is and go from there. centerline method should be fool proof.

My cam card shows open at 30.5 at .050 and I get 29. Cam is installed at 105.25. Closing spec is 58.5 and I get 57 .050 before close. So that is real close. I have a gentleman over on speed talk tell me to use .020 to center the cam with asymmetrical lobes. I am still trying to figure duration at .200 lobe lift. Do I read the wheel for this or is it a math equation? Spec is 190 lobe lift at .200.

Also, bullet says not to use the lifter bore tool for measuring any cam specs. If roller, must use a lifter because of the wheel size. Mine are .810 wheels. Doing this does seem to get more accurate measures.

For duration at 0.200 you just read the numbers on the wheel as you turn the cam from 0.200 to 0.200. When you go past TDC you need to keep track of what you are doing.

Follow your cam card and ignore the guy on Speedtalk telling you to do something else. You have the cam card, use it. If you don't understand the cam card then call the mfg. People on Speedtalk argue with everything and everybody just for fun.

Isnt your cam installed 2 degrees retarded? If so, the @.050 numbers line up close enough. Lifter bore bank angle and plane errors can move the @.050 numbers around quite a bit.

Send it.

Ok, thanks Andy. I will give that a try tomorrow.

You have to degree off of the events not intake center line

Yes, its close. Just need to check v/p clearance. I am now at truely 105* centerlined. The numbers on the card are very close.

104

Uh-huh...couldn't agree more...that fancy looking CompCams tool caused me a massive headache as I attempted to degree my mild hydraulic roller. Eventually, degreeing off of an actual roller lifter got me the matching numbers.

Don't say "don't use lifter bore tool".
There are different lifter bore tools with different diameters.
I machined my own. My "tool" has a 0.810" dia ball on the end. One man's tool is different than another. And Comp's tool might have small balls...

And I use the 0.050" numbers for discussion. But I have measured the centerline at many lobe lifts for info. It can vary. But 2 degrees either way doesn't mean one number is best for your engines combination.

Just went through this. Measured @.050" open and close. Also C/L @ .070", .050", .030" before max lift. None are quite the same. In fact duration was longer than the card showed. The bottom line is advance it further than you'll ever need and check intake P to V. Retard it to far and measure exhaust P to V. Then stab it in close to where you think it should be, by whatever method you chose. Then when it's up and running you can move it with confidence. You'll never no what's best unless you try different spots.
Doug

Yes, i will have to see what my clearances are at my current 105* install and go from there.

It’s okay Charlie....... I know what you’re saying there.

On the other hand, when the VP clearance is marginal....... it may have to be installed wherever it fits.

Something else Bullet told me yesterday has me wondering if they know what their talking about. They say for p/v clearance that .060/.060 is ok. .060 sounds tight on exhaust from what I have been reading. Steve Morris says intake .050/.080 exhaust as minimums.I am way more inclined to believe Morris on this issue.

This.

Unless you put it in, measure it, test it, change it and test again, it is just a fruitless weedy discussion.

Thinking that the recommended centerline is actually the best centerline is a bit of a stretch, let alone argueing about 0.050", 0.200" or 0.050" over the nose methods, IMO.

My Com Cam instructions says to use over the nose equal amounts, fwiw.

Machine shop was busy, so i installed the exhaust valve, checking margin with blue dykem or whatever its called. Looked good to me as well as the install height being the same, so mounted the head back up and remeasured with checking springs. I get .051 on intake and .088 on exhaust. Cam is in at 105. Looks like the best i'm gonna do, but maybe a 1.5 rocker would get me a bit more clearance as Dwayne suggested. The valve events measured are as i stated before, intake open 29 close 57, exhaust open 71 close 29.5. The exhaust closing point is off by 4* not sure why as the other events are 1.5* different.

Intake atdc Exhaust btdc
0*-.082 0*-.120
5*-.057 5*-.097
6*-.056 6*-.092
7*-.051 7*-.090
8*-.052 8*-.088
9*-.052 9*-.088
10*-.054 10*-.089
15*-.070 11*-.090
I will install the roller springs and remeasure again with clay tomorrow.

Your golden with .050 intake and .080 on the exhaust, don't forget that the aluminum head will get taller when warmed up moving the valves further away from the pistons
Trust me on that, I know guys that circulate hot water through their engine builds that have seen and measure the difference It will get more clearance warm or hot, not less

Agree. The Comp lifter bore tool is good for centerline method where lifter diameter / roller size just needs to be the same on each side of max lift, but not good for open/closing events. For opening / closing events use the lifter that will be run.

The exhaust is closest before tdc. I don't understand the chart you posted. The piston chases the exhaust, it cant be closer after tdc. Once piston hits tdc they are going opposite directions. Are the ex number before tdc?

sorry for the confusion, i thought anyone would figure it out. the ex side should also be read from bottom to top to make things clear.

Interesting. I never saw a cam card with different rocker ratios. 1.6 on the intake and 1.5 on the exhaust.
0.430 x 1.6 = 0.688
0.430 x 1.5 - 0.645
Typically I had to calculate the lift for the ratio I am using if the cam card was for 1.5.

no problem just making sure.

Its cool, just want to be clear. The clay measure was kind of a bust. I measured .114 on intake and .122 on exhaust using clay. Not sure why, the clay is firm and not spongy at all. I'm done measuring. Its now time to get this back together. Thanks guys

So your radial clearance was good also?I know if the clay is laid too thick it will curl around the valve when pressed.

I had .060 radial. Didn't see any issues there.

That is exactly what I expected.

https://rehermorrison.com/tech-talk...piston-to-valve-clearance-the-right-way/

Those guys are sharp. I did try this last week, but my LSM spring pressure checker is too large to get a dial indicator in there. I will give that another try next week when i have some more time.

There is nothing wrong with clay, as long you don't over do it/ do it correctly. People use plastiguage don't they?