[BillyGman]

This is from UDHarold:

I have stayed out of this because of the Flu, but here's what I have done for 31 years.
1---Find TDC
2---Turn up to max lobe lift.
3---Zero your dial indicator.
4---Turn the engine backwards .100".
5---Turn it forwards to .050", which should be .050" before max lobe lift.
6---Record this number as degrees ATDC.
7---Continue to turn the engine forward, to max lobe lift, and .050" down.
8---Record this number as degrees ATDC also. IAt will be close to BBDC.
9---Add the 2 numbers together, and divide by 2. This is your intake CL.

You can put the cam in by the intake CL. If you must know the exhaust CL, repeat the steps on the exhaust cam. Those numbers will be BTDC.

This works with symetric and unsymetric cams, but is a necessity for unsymetric cams.
Bill Jenkins taught me this method when I was doing his cams at General Kinetics. It is the quickest, and most accurate, method to use.

 

[nashville beth]

You clarified later but your instructions could have been a little clearer: Find TDC on #1. Turn up to max lobe lift on the #1 intake lobe
Thanks for posting this ! I will use it to check my ZZ502 cam

 

[BillyGman]

You clarified later but your instructions could have been a little clearer: Find TDC on #1. Turn up to max lobe lift on the #1 intake lobe
Thanks for posting this ! I will use it to check my ZZ502 cam

Beth, those aren't my words in my previous post. It's a quote from the late great cam designer Harold Brookshire, (AKA "UDharold"). So they were Harold's instructions. Not mine. It's a better method he recommended for finding the intake center line. And it's always the ICL which is used to degree-in a cam. But thanks for chiming in about that.

 

[jeff swisher]

I just did this 4 days ago on a [email protected] .050 cam with 114 LSA.
Straight up it was at 107 Intake centerline.
My summit true roller timing chain set allows 4 degrees advance.
When advanced so called 4 degrees it was actually at 100° Intake centerline.
Good things to check.

Looks like that 4 degrees is actually 7°.
I then wanted to play around and retarded it "4" with the gear and advanced the cam gear 1 tooth.
I got 97° intake centerline.

It is running now bet I set it at 107° Intake centerline.

 

[nashville beth]

Beth, those aren't my words in my previous post. It's a quote from the late great cam designer Harold Brookshire, (AKA "UDharold"). So they were Harold's instructions. Not mine. It's a better method he recommended for finding the intake center line. And it's always the ICL which is used to degree-in a cam. But thanks for chiming in about that.

I can visualize UD Harold's sarcastic look if I offered to "improve" his instructions. LOL
That is a simple method ! And I will use it soon. Thanks !

 

[BillyGman]

Oh, and let's not forget Harold's "quick & dirty" method for making sure if you installed the cam correctly with the timing gear the way it should be, (of course this only works if the exhaust and intake valves have the same installed height, which I believe in most applications they do):


"If the cam is already in and you want to check, use my 'Quick-n-Dirty' method......
Take off the driver's side valve cover, turn the engine to TDC. If Nr 1 cylinder has both valves on the seat, turn the engine over again.
Both valves should be OFF the seat at TDC, and Nr 6's valves should both be ON the seat.
Using something like a Machinist's 6" Steel Rule, measure from the spring seat to the top of the retainer, 1st on intake, then on exhaust.
The intake retainer should be .030" to .060" CLOSER to the head than the exhaust retainer. If it measures anywhere in that range, it is in the engine just fine, and will run good.
If the exhaust retainer is closer to the head, the cam is retarded, and you need to advance it.
Always recheck after moving the cam.....
This system has worked for over 20 years.

UDHarold"

 

[steelcomp]

This method can get you in trouble with asymmetric lobes...asymmetric meaning "not the same on both sides" meaning .050" lobe lift may not be the same number of degrees each side of peak lobe lift. This is why I always recommend installing a cam per the intake opening event @ .05 and not the lobe c/l. I've seen as much as 7* difference between the two using the above method.

 

[BillyGman]

This method can get you in trouble with asymmetric lobes..

Hmmm....then I wonder why Harold said this- "This works with symetric and unsymetric cams, but is a necessity for unsymetric cams."

.... This is why I always recommend installing a cam per the intake opening event @ .05 and not the lobe c/l.

You got me on that one Scott. I'm not following you here^^^ I must admit that I've never heard of that, and because I've never heard nor seen it done that way, I wouldn't even know how to carry that out in practice. Are you saying that the exact opening event should be found with the dial indicator, and then turn the engine until the indicator shows .050" more? If so, then what?

I'm not getting a clear picture in my mind of what you're suggesting. Sorry if I'm asking a novice type question. Perhaps I'm just failing to recognize your terminology. But I wasn't aware that there's another method to degree a camshaft other than finding the ICL.

 

[70GS455]

There has been a huge discussion about this topic on Speedtalk. Harold himself has weighed in on the topic years ago. The procedure you outlined is the center of the point of maximum lift. For a non-symmetrical cam, it's not really the center line of anything, except the upper lift area.

Engines don't really care about where maximum lift occurs. They care mostly about the valve events. So checking the midpoint of valve events (notice I didn't say centerline) is much more meaningful.

However, the point of maximum lift centerline gives us a common reference we can all relate to when we sit around and tell campfire stories and compare results from back in the days when cams were symmetric and centerline meant centerline, no matter where it was checked.

And when we start talking about centerline, we are really referring to where the valve events are occurring. Those terms used to be interchangeable, but no so much with an asymmetric profile

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[BillyGman]

There has been a huge discussion about this topic on Speedtalk. Harold himself has weighed in on the topic years ago. The procedure you outlined is the center of the point of maximum lift. For a non-symmetrical cam, it's not really the center line of anything, except the upper lift area.

Engines don't really care about where maximum lift occurs. They care mostly about the valve events. So checking the midpoint of valve events (notice I didn't say centerline) is much more meaningful.

However, the point of maximum lift centerline gives us a common reference we can all relate to when we sit around and tell campfire stories and compare results from back in the days when cams were symmetric and centerline meant centerline, no matter where it was checked.

And when we start talking about centerline, we are really referring to where the valve events are occurring. Those terms used to be interchangeable, but no so much with an asymmetric profile

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Scott, thank you for chiming in here on this. I perfectly understand your point about the need to find the center point between the opening and closing events of the intake valve. But what I don't understand is exactly how that can be done. I suppose I would be able to figure it out for myself by using my dial indicator and lifter bore tool. But I've never seen that method written about in any cam degree instructions I've looked at be they in printed form or in a video.

So I take it that the valve events would need to be found with the dial indicator, and then with a degree wheel installed on the crank, the number of crankshaft degrees between those two points where the intake valve first opens and when it first closes has to be observed on the degree wheel, and then half of that is the number we want? But then what do we do with that number since there's only the ICL number on the cam card? How does that number of half the crankshaft degrees between the intake opening and the intake closing event help us to know if the camshaft is installed in the correct timing position if the only thing the cam card gives us will be the ICL number?

 

[77 cruiser]

I guess if your cam card only shows ICL that's the way you'd have to do it. Last cam I did was the one from Chris & I installed it degreed to opening & closing & checked max lift CL & it was different by about 3-4 degrees but I can't remember which way.

 

[ML67]

This method can get you in trouble with asymmetric lobes...asymmetric meaning "not the same on both sides" meaning .050" lobe lift may not be the same number of degrees each side of peak lobe lift. This is why I always recommend installing a cam per the intake opening event @ .05 and not the lobe c/l. I've seen as much as 7* difference between the two using the above method.

I did an in car cam swap this winter, and frankly struggled w/ the former method. Using the intake (and exh) using .050 opening event worked perfectly. My experience mimics precisely what Scott posted.

 

[BillyGman]

I guess if your cam card only shows ICL that's the way you'd have to do it. Last cam I did was the one from Chris & I installed it degreed to opening & closing & checked max lift CL & it was different by about 3-4 degrees but I can't remember which way.

Well until I can grasp and learn what it is you guys are talking about, I guess I'll just have to use the ICL method because all my cam cards list the opening and closing events of the intake and exhaust valves, but I still don't get how you guys are using the valve events to degree a camshaft. Like I said, I've never seen it done that way in any of the vids I watched, nor seen it described step by step in any of the cam degree instructions that I've read. But I'll do a search.

 

[steelcomp]

Well until I can grasp and learn what it is you guys are talking about, I guess I'll just have to use the ICL method because all my cam cards list the opening and closing events of the intake and exhaust valves, but I still don't get how you guys are using the valve events to degree a camshaft. Like I said, I've never seen it done that way in any of the vids I watched, nor seen it described step by step in any of the cam degree instructions that I've read. But I'll do a search.

Bill, if you look at your cam card, it should tell you what the valve opening and closing events are at .050" (lifter rise). Most will say "Timing Events @ .05" "
Set up your degree wheel just like you were going to do the centerline method but instead, when the respective lifter reaches .050" lift, read the degree wheel and compare that with what's on the card. I use and recommend using the intake opening event. Personally, I like to see a little advance, like maybe 1 to 1-1/2 degrees to allow for chain stretch and deflection in the valve train. Some degree wheels are even marked to show the general areas where the events should take place. Most intake opening events will be BTDC and will be a positive number but if the card shows a negative number like -5, then it will be ATDC. Hope that helps.

 

[Aml383]

Bill, if you look at your cam card, it should tell you what the valve opening and closing events are at .050" (lifter rise). Most will say "Timing Events @ .05" "
Set up your degree wheel just like you were going to do the centerline method but instead, when the respective lifter reaches .050" lift, read the degree wheel and compare that with what's on the card. I use and recommend using the intake opening event. Personally, I like to see a little advance, like maybe 1 to 1-1/2 degrees to allow for chain stretch and deflection in the valve train. Some degree wheels are even marked to show the general areas where the events should take place. Most intake opening events will be BTDC and will be a positive number but if the card shows a negative number like -5, then it will be ATDC. Hope that helps.

Wow

 

[Humberd]

Very interesting thread , I am still learning a lot
About cam timing 😎

 

[BillyGman]

Bill, if you look at your cam card, it should tell you what the valve opening and closing events are at .050" (lifter rise). Most will say "Timing Events @ .05" "
Set up your degree wheel just like you were going to do the centerline method but instead, when the respective lifter reaches .050" lift, read the degree wheel and compare that with what's on the card. I use and recommend using the intake opening event. Personally, I like to see a little advance, like maybe 1 to 1-1/2 degrees to allow for chain stretch and deflection in the valve train. Some degree wheels are even marked to show the general areas where the events should take place. Most intake opening events will be BTDC and will be a positive number but if the card shows a negative number like -5, then it will be ATDC. Hope that helps.

OK Scott, I've got it now. Obviously that sure is easy enough. In my mind I was making this out to be more complicated than it really is. I appreciate you being patient with me on this. Thanks for your explanation on that, and also thanks for the 1 to 1 1/2 degree compensation for chain stretch and valve train flex comment. That makes a whole lot of sense.

 

[70GS455]

Scott, thank you for chiming in here on this. I perfectly understand your point about the need to find the center point between the opening and closing events of the intake valve. But what I don't understand is exactly how that can be done. I suppose I would be able to figure it out for myself by using my dial indicator and lifter bore tool. But I've never seen that method written about in any cam degree instructions I've looked at be they in printed form or in a video.

So I take it that the valve events would need to be found with the dial indicator, and then with a degree wheel installed on the crank, the number of crankshaft degrees between those two points where the intake valve first opens and when it first closes has to be observed on the degree wheel, and then half of that is the number we want? But then what do we do with that number since there's only the ICL number on the cam card? How does that number of half the crankshaft degrees between the intake opening and the intake closing event help us to know if the camshaft is installed in the correct timing position if the only thing the cam card gives us will be the ICL number?

Billy, yes just like was described by others, using the 0.050" valve event numbers on the cam card and picking one ( I use IC but IO works also), will get us much closer to the actual valve events.

There is one more caveat to consider here also. For a non-symmetric cam, the program that the manufacturer uses to generate the cam card valve event numbers will make a difference. If the program uses the actual numbers from the engineering file used to generate the lobe, then all is good and the asymmetry has already been taken into account. However, if the program used to print the cam card numbers simply assumes that the profile is symmetric, and generates the events from the ICL and half the duration, then the center will be off. For example, IO = (50_duration / 2 - ICL), IC = (50_duration / 2 + ICL ) - 180, etc

This second scenario happened to me on a cam from company "B" that I was trying to degree. I was getting 3 different answer for ICL using 3 methods: point of maximum lift, card 50 valve events and advertised events. I asked and they did give me the numbers from the engineering file at 6 and 50, then I was able to get answers that matched. The file numbers were different from the card numbers (not by a lot but different)

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[BillyGman]

Billy, yes just like was described by others, using the 0.050" valve event numbers on the cam card and picking one ( I use IC but IO works also), will get us much closer to the actual valve events.

There is one more caveat to consider here also. For a non-symmetric cam, the program that the manufacturer uses to generate the cam card valve event numbers will make a difference. If the program uses the actual numbers from the engineering file used to generate the lobe, then all is good and the asymmetry has already been taken into account. However, if the program used to print the cam card numbers simply assumes that the profile is symmetric, and generates the events from the ICL and half the duration, then the center will be off. For example, IO = (50_duration / 2 - ICL), IC = (50_duration / 2 + ICL ) - 180, etc

This second scenario happened to me on a cam from company "B" that I was trying to degree. I was getting 3 different answer for ICL using 3 methods: point of maximum lift, card 50 valve events and advertised events. I asked and they did give me the numbers from the engineering file at 6 and 50, then I was able to get answers that matched. The file numbers were different from the card numbers (not by a lot but different)

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I was wondering that. If that is the case, then there's probably no point in even degreeing a cam with asymmetrical lobes in the first place. Unless you get the cam company in question to go the extra mile for you over the telephone like you did, (and some cam techs might not be willing to do that) then we might as well simply line up the timing marks on the gears, and call it a day.

 

[steelcomp]

Billy, yes just like was described by others, using the 0.050" valve event numbers on the cam card and picking one ( I use IC but IO works also), will get us much closer to the actual valve events.

There is one more caveat to consider here also. For a non-symmetric cam, the program that the manufacturer uses to generate the cam card valve event numbers will make a difference. If the program uses the actual numbers from the engineering file used to generate the lobe, then all is good and the asymmetry has already been taken into account. However, if the program used to print the cam card numbers simply assumes that the profile is symmetric, and generates the events from the ICL and half the duration, then the center will be off. For example, IO = (50_duration / 2 - ICL), IC = (50_duration / 2 + ICL ) - 180, etc

This second scenario happened to me on a cam from company "B" that I was trying to degree. I was getting 3 different answer for ICL using 3 methods: point of maximum lift, card 50 valve events and advertised events. I asked and they did give me the numbers from the engineering file at 6 and 50, then I was able to get answers that matched. The file numbers were different from the card numbers (not by a lot but different)

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If you're going to go that far you might as well find someone with a cam Dr and check every lobe on the cam. Sometimes you have to pick your battles.