Camshaft profile design - hard on parts?

[la360]

This is a question for those folk experienced with building Comp Style engines. When does the camshaft profile design start to be hard on, and regularly hurt valvetrain parts?
I have been given a ball park kind of figure, but wasn't able to expand on it during the phone conversation due to time.
Just to give you some parameters, I am talking small block engine, 50-60MM Core, Titanium valves, Jesel style rockers etc.
Would be interested to hear peoples thoughts, and about their experiences, this style of engine is relatively new to me
Many thanks
AL Jones

[bigjoe1]

If you are dealing with the right camshaft company, this should NEVER a problem. I work with Comp Cams, and I talk to the senior camshaft designer on a regular bassis. He tells me what his favorite grinds are, and you can be sure, if he is very proud of it, it is going to be his best work. He is also in a position to tell me which grinds to stay away from. A company like Comp has two or three spintron machines that they can test the new cam designs on before they released them to the public. On a similiar note, as you add on rockerarm ratio, the cam gets much more violent.
JOE SHERMAN RACING

[Windsor377]

You're valtrain will begin to hurt itself when the harmonics get out of control. I prefer not to have a set of numbers that I consider good or bad, but rely heavily on my cam supplier to fully understand my combination and goals before I get a set of recommendations.

For example I have 2 cams right now that make an interesting point.

They both have very similar numbers but one has a little taller labe than the other. The one with the taller lobe will go to 10K + rpm with a 1.85 rocker. The other I have the high side set at 8.8k with a 1.7 rocker. Any higher would be playing with fate.

Also I'd recommend nothing smaller than a 55mm core.

[Racer7088]

This is a question for those folk experienced with building Comp Style engines. When does the camshaft profile design start to be hard on, and regularly hurt valvetrain parts?
I have been given a ball park kind of figure, but wasn't able to expand on it during the phone conversation due to time.
Just to give you some parameters, I am talking small block engine, 50-60MM Core, Titanium valves, Jesel style rockers etc.
Would be interested to hear peoples thoughts, and about their experiences, this style of engine is relatively new to me
Many thanks
AL Jones

You simply have to know about valvetrain when you are turning 8000+ rpm no matter what. If you don't feel good about making a decision totally on your own and you probably don't right now or you wouldn't be trying to expand your knoqwledge, then do as these guys are telling you and get some first hand knowledge from the cam guys themsleves about what is generally run. They can give you some pretty stable systems and lobes that you shouldn't have any problems with.

You can use lobes that are made to turn 10000 rpm and last a while and then there are lobes that are made to be much more agressive and will eat springs and valvetrain parts right and left. If you don't have lots of time and money to test then get an engineered and tested setup that can turn even more rpm then you think you will, to stay on the safe side of things.

Also be honest with yourself about how much rpm you can afford and what parts you can really run as well as how long they need to last and you'll make a much better decicion in the end when you're talking o these guys. Then after every high rpm engine you do you will start developing your own experiences and understandings further and further and can keep building on them as well as making more intelligent choices even when talking with other engine guys like here on Speedtalk. Good luck.

[la360]

I won't be picking the camshaft profile, and have been advised on part selection by a friend who builds Comp Eliminator engines on a regular basis. He has been more than helpful with explaining certain aspects of lobe design etc. Just trying to save some $$$ on long distance calls, and I am sure he has better things to do than sit on the phone with me for hours, lol
Thanks
AL....

[Racer7088]

Hey well at least it sounds like you already have one good guy on your side. I am sure there are many on this site that could help you out too. Good luck on that engine it dounds pretty mean.

[Windsor377]

I won't be picking the camshaft profile, and have been advised on part selection by a friend who builds Comp Eliminator engines on a regular basis. He has been more than helpful with explaining certain aspects of lobe design etc. Just trying to save some $$$ on long distance calls, and I am sure he has better things to do than sit on the phone with me for hours, lol
Thanks
AL....

AL,

I consult and share information with some folks overseas. One thing I do when I know we are getting into an area that needs some thought time is I'll send an email laying out the information in as much detail as possible about what we need to discuss. Then when the phone call is made, plenty of thought has occured in advance and we can use the email like a check list for the discussion. Not to say we don't deviate, but there is less time spent trying to figure things out.

[la360]

I wouldn't be doing what I am doing without my friends help, his advise has been invaluable.

As I don't have them in front of me, does anyone have an idea of how much the base circle increases going from a 50mm-60mm-70mm camshaft.
Does the base circle increase to a similar percentage of the journal diameter? Or is this far too much of a general question?
Thanks for the replies
AL...

[Windsor377]

You can still wind up with base circles all over the map with the larger core. HOWEVER, think of it this way; if you have a 50mm core and your lobe lift is maxed out, switching to a larger core lets you increase the base circle by the amount you increase the core size and still have the same lift.

What this allows you to do is spread the lifter acceleration stresses out over a greater area.

PS. Then on the flip side, if your existing base circle will support more lift, but your existing core size wont, going to the large core allows room to increase the lobe lift by 1/2 the difference in the core sizes.

[UDHarold]

I have several ramp design families that I have been using for the past 16 months, an aggressive 28* Major Intensity family that has worked fine in the lower 8000 range--No broken valve springs on any cams reported--and a 31* Major Intensity family I use for Comp engines, AND for street/strip cars. It has been spintron tested to over 9300, and the ramp opening and seating rates are those I used in an earlier 24-Hour of Daytona winner. I have had no failures, street or strip, with this family, either.
I make the 28* MI family from .3933" to .4544" lobe lifts, in various durations.
I make the 31* MI family from .3667" to .5300" lobe lifts, again, various durations.
My biggest problem so far has been finding semi-finished cam cores with sufficient high lift area to grind the cams without going into the core. I have ruined several cores in the past month, .4854" to .5300" lobe lift, because of insufficient high lift grind stock.
All my cams are designed for the journal-size being used, so there is no "duration-growth" using larger journals.
I also have less-aggressive, higher-RPM cams if necessary.
Some of the 28* ramps cannot be ground on small-base-circle SBC cams.

UDHarold

[OldSStroker]

My biggest problem so far has been finding semi-finished cam cores with sufficient high lift area to grind the cams without going into the core. I have ruined several cores in the past month, .4854" to .5300" lobe lift, because of insufficient high lift grind stock.

UDHarold

Are you using carburized 8620 cores? Have you tried 5150 cores with induction hardened lobes? Depending on how the induction is done, that might get the case depth you need.

[UDHarold]

I use 8620 and 8660 cores, the 8660 are induction hardened, but the problem is not the depth of heat-treat, but the lack of high-lift duration.
Some of my larger pro/comp exhausts lobes have more nose radius than they have base circle radius.
Camshaft Machine Company(CMC), who make the 8660 cores require large numbers of cores to be ordered before changing their existing designs.
CamMotion makes an extremely wide variety of 8620 cores for the SBC/BBC.
If I ever get into the core-making business, I will use 8660 as one of my steels.

UDHarold

[la360]

What kind of differences do you see in Duration @ 0.020" and Duration @0.050" with these 28* MI & 31* MI lobe families?
I'd be looking at something with around 0.500" lobe lift with a 1.7:1 intake rocker.
Thanks Harold
AL Jones....

[camman]

[quote="UDHarold"]
CamMotion makes an extremely wide variety of 8620 cores for the SBC/BBC.
If I ever get into the core-making business, I will use 8660 as one of my steels.



The Cam Motion custom cores are fantastic value, The 8620 they use is a lead free bearing grade and ask them about 9310 if you really want your cams to last. It is similar to a EN39B. fantastic core strength and hardness of around 62RC on the lobes with good depth.


Anaditional answer to the first question. The lobe design has a lot to do with it but even once you have a nice lobe it is then about how that lobe interacts with the associated parts, spring frequency, pushrod frequency, rocker arm stifness etc. all of which should be worked out for you by your cam guy so you get a package thet gels together real nice.

[rmcomprandy]

la360 -
unless something has changed in the world of camshafts over the last few months the 28° and 31° intensity -IS- the difference between durations @.020" & @.050".