I'm about to help my buddy degree his cam tonight and need some input. When I have done this in the past, I established the intake centerline by putting the dial indicater on the lifter . Comp Cams recomends that you should place it on the valve spring retainer, they say that this way you have all the valve train "slop" figured into your set up. This is exactly why I prefer ot use the lifter, it eliminates the possibility of your settings being off due to rocker arms/studs. What do you think??

 

Hmmmmm i'd try both to see whats up

 

well, you're degreeing the cam to judge VALVE events - not lifter events.

Seems to me that if there is going to be "slop" related to rocker arms/springs/etc, then you might as well take it into consideration rather than ignore it. After all, appropriate valve events are what you're trying to measure and set. Just make sure you account for non-primed hydraulic lifters (no oil in them), etc.

 

I think u need to use a solid lifter - then won't need to install hyd lifters on cam before break-in while degree'n. Low rpm/rotation will kill a hyd cam - i have proven this for myself.
I made a long solid lifter out'a 2 hyd lifters BTW - works great.

cardo0

 

Currently there are two popular methods for degreeing a cam, the centerline method, and the duration at .050" lift method. Of the two methods, the duration at .050" lift is much more accurate.

The main problem with the centerline method is it has you finding the theoretical centerline of the intake and/or exhaust lobe and line up on it.
It makes the basic assumption that the lobe you are checking is symmetrical, with its opening side being the exact same shape and size as the closing side of the lobe.
The truth is that most modern lobes are asymmetrical, with the opening side of the lobe being much more aggressive and the closing side being more gentle.

Therefore, when you attempt to locate the middle (or centerline) of the asymmetrical lobe there is an automatic error factor. It could be as little as 2° off or as much as 6°, depending on the exact lobe shape and the procedure used during the degreeing operation.
Neither does it verify that the camshaft has been properly ground with the correct duration lobes, which can drastically affect performance.
Since the duration at .050" lift method is not affected by the asymmetrical lobe design, I think it is the more accurate way to degree.


my .02¢
Hope it helps,
Chuck

 

The reason they say to take it of the valve spring retainer is to take into acount any valve train geometry differences, as well as the assymetrical differences described in the above thread.

 

Taking readings from the spring retainer won't change the shape of the lobe.



Is that why YOU degree a cam? Most of us degree a can to verify that the cam was ground and installed properly. If there is a problem with either, that is the time to advance or retard the cam to make corrections. Any slop or inaccuracies that might occur between the lifter and the retainer only corrupts the readings and therefore information gathered.



Hogwash! A flat tappet HYDRAULIC lifter isn't any harder on a cam than it's solid equivalent. Solid lifter flat tappet cams (with either type lifter) are equally vulnerable to slow, full load, lifter damage.

RACE ON!!!

 

I disagree with Vett-66, where he said,
"Currently there are two popular methods for degreeing a cam, the centerline method, and the duration at .050" lift method. Of the two methods, the duration at .050" lift is much more accurate".

When I degreed my Comp Cams custom steel billet roller cam in the 540 big block I'm building right now, I tested both methods. The intake centerline was the only accurate method, it is using the centerline of the TIP of the lobe, it doesn't care if the lobe is symmetrical or not, that isn't the issue at all, only the lobe positioning.

The .050 method will be almost certain to mess you up, because the base circle on any cam I have ever checked, has a slight variation in it's machining. So zero on the dial indicator is a moving target, you can't know for sure where to start reading for that .050 lift. I found it could cause the timing to be off by a few degrees. Kinda defeats the whole idea of degreeing the cam, doesn't it? That's why cam manufacturers call for the intake centerline method, because it is dead reliable and precise.

I also recommend degreeing the cam at the lifter bore, because the whole point is to degree the cam relative to the crank. It is the most accurate there, since up top flex, if you aren't using checking springs, rocker geometry and variations in rocker arm ratio can affect what you are doing, if you try to do it at the retainer. You may change the parts up top over time also, so it doesn't make sense for that to affect your cam timing. BTW keep in mind that .050 tappet lift means lobe or lifter lift, not valve lift. If you try to simply multiply .050 tappet lift by your rocker ratio, and use that at the retainer, you will end up off a bit on your timing, again defeating the whole purpose. If you precisely measure lobe lift vs valve lift you will see that it is never the same as a simple math calculation would suggest, due to real world parts and rocker geometry variation.

Do yourself a favor, use the intake centerline method at the lifter bore, and you will be good to go, with excellent accuracy.

 

 

nevermind.

 

Hogwash! A flat tappet HYDRAULIC lifter isn't any harder on a cam than it's solid equivalent. Solid lifter flat tappet cams (with either type lifter) are equally vulnerable to slow, full load, lifter damage.
RACE ON!!!

What a waste of hard earned good information. If someone can't understand the difference between using 1 large solid lifter as a cam follower tool - without the p-rod and spring assembly installed - rather than as hyd lifter preloaded under vlv spring press, they're not worth any effort to explain further. To misinterpret my to post as implying installing a complete solid lifter set to avoid lifter damage is truly Hogwash in itself!!

BTW folks the .050" delta is measured on each side of lobe peak in degrees then divided by 2 - not .050" from the base circle.

Anyways since Jimmy, the post originator, hasn't responded to anything posted yet, i see very few sincere participants to help here. More like a circle j__k that attracts the usual crowd.

cardo0

 

And where in this post did you state "1 large solid lifter as a cam follower tool - without the p-rod and spring assembly installed - rather than as hyd lifter preloaded under vlv spring press"? And where did you state that was better, opposed to, "rather than as hyd lifter preloaded under vlv spring press". I implied nothing. It is hard to misinterpret what isn't stated. Where was it understood that the hydraulic lifter had to be installed with the complete valve train for that cylinder? Are you ASSUMING things? Don't get all over MY case because *I* didn't ASSUME what wasn't said.

I have to agree with that last statement. Except YOU were the only "circle j__ker" that showed up.

RACE ON!!!

 

I degreed the cam weeks ago, we had trouble getting consistant readings on the piston stop through the spark-plug hole, so we pulled the head and used a piston stop that bolts to the deck. With the head off we did not have the option of using the valve spring retainer. By the way, you always use a well lubed solid lifter to degree a cam. It could be a modified hydraulic, altered to behave like a solid. Remember when you come off the lifter you don't have the valve spring load pushing on the cam, so you don't have to worry about about wiping out the cam as you would on start-up.

 

This makes the most sense of most anything posted. You may have also heard of this as being the ".050 down method"

One additional pointer though: always rotate the motor the same direction-- never reverse it. It'll only skew your figures.

When your dial indicator is at .050 on the way up, mark your degree reading, then after peak lift (on the way down) take your degree reading at the .050 dial indication again. Mark your degree reading again.

This is, of course, works if the cam is "symmetrical". If the cam is not symmetrical, all bets are off with the slower ramp down. (as mentioned earlier, non-sym cams have more agressive opening ramps than closing ramps.

 

Thx for posting your results Jimmy and sorry for the delay in my response - tax time u know.
Yea i didn't like the aftermarket piston stop i paid for as it seemed to bend with each rotation stop - but now i think it was just not locked well enough in place to holp in position. Anyways i make my own now from old sparkplugs and cheap mushroom headed stove bolts 3/8"NCx3". But i use a backup nut to lock down the bolt inside the plug casing and no longer have problems with the stop drifting. Just thread it all the way in and snug it down with the b.u. nut - close to 20* each side of TDC on a sb Chevy (BB may need bigger bolt).
Glad to see you got my message using the solid lifter unloaded.


Aquaman, thx for elaborating the details here for cam degreeing the lobe centerline. That was John Lingenfelters method (may he rest in peace) and his reasoning was that the asymetric difference in ramps at the top of lobe would be much less significant than at the base. Also the .050" is only arbitrary and one can use any distance he chooses as long as it is the same distance from the top of the lobe - once the dial stops moving zero the indicator and choose a distance.

And i can see there is a lot more talented people with good exprience listining here but may not want to come forward to share thier notes and have to deal with the bad mouthing or all the fault-finding.
cardo0

 

Like THIS.

RACE ON!!!