33 replies to this topic

[CarolinaTZ]

Hi, I checked around so not to ask a redundant question but couldn't find anything. I have Racer Brown cam with:

110 SS56 - SS54
485-2

The numbers seem to be a combination of 2 different grinds...SS56 and SS54. Has anyone seen a number like this or know what the specs are? The date appears to be 1985.

Thanks,
Joe

Edited by CarolinaTZ, 01 November 2010 - 06:26 AM.

[JMortensen]

If you don't have any luck with the numbers, you can put it in some V blocks, spin it and use a dial indicator to get lift. Then multiply that by 1.5 and there's your lift at the valve. You might be able to match up the intake and exhaust lift with a known Racer Brown profile that way...

[tube80z]

Since I'm posting I'll probably be wrong but I remember those a hot street grind. A lot of lift and short duration. I think somewhere in the 475 to 495 lift range but shorter than stock duration. I had one in a street car in the eighties and it was NOISY. The aggressive ramps seemed to about double the valvetrain noise. I'll have to see if I can find my original BRE book as they were listed in it.

Cary

[CarolinaTZ]

Thanks for the help, guys. How well did the cam perform? This cam is in my motor that Tom Wyatt built so, I assume it's a good cam for a turbo motor. Do turbos like a lot of overlap or not? The steep profile/high lift may explain some wear on some of the lobes. Can cams be repaired? If so, who do you guys recommend? I haven't taken any measurements yet...this is based on visual.

Edited by CarolinaTZ, 04 November 2010 - 05:56 AM.

[Tony D]

"Can cams be repaired? If so, who do you guys recommend?"

Paeco in Birmingham Alabama markets a hardfacing compound welded on journals and cam lobes (price of repair is based per lobe/journal)

The issue is whether or not you can get the orginal grind replicated! Racer Brown used assymetric lobe profiles and once welded over, if not shadow-profiled (Isky can do this...) and then properly programmed into the grinding machine will be lost forever.

It may simply be cheaper to map the specs as best you can, and then talk to Isky or Sunbelt about what grind they have available to approximate it. They are the only two that I know of that are currently grinding assymetric cam profiles for the L-Engine.

[Xnke]

My cam from delta is an assymetric, but it's not a new grind...it's very obvious from looking at the lobes what type it is, though. I would imagine it's a knock off of another cam from the late 70's early 80's, but Isky and Sunbelt are not the only ones.

[Tony D]

News to me, then it would be Delta Sunbelt and Isky. Other stuff I've seen is old tech bumpstick profile. If Delta knocked something off, it would be Racer Brown if it was the 70's. They were the only one selling asymetric grinds for the L Series then. Isky didn't go assymetric till the early 80's.

[JMortensen]

I had two different American Cams regrinds in my Z. Both asymmetric.

[TimZ]

News to me, then it would be Delta Sunbelt and Isky. Other stuff I've seen is old tech bumpstick profile. If Delta knocked something off, it would be Racer Brown if it was the 70's. They were the only one selling asymetric grinds for the L Series then. Isky didn't go assymetric till the early 80's.

You may still be correct, Tony. As you know, you can't tell if a grind is asymmetric or not just by looking at the lobe - you have to map the actual lift that occurs at the valve vs engine rotation. Because of the way the geometry changes as the lobe wipes over the rocker, the lobe for our engines ends up looking asymmetric just to keep the actual lift profile symmetrical.

My current cam lobes look for all the world to be asymmetric, but here's a plot of the opening/closing rates at overlap - the ramp rates are pretty much identical. When I mapped the whole thing I was really surprised at how symmetrical the intake and exhaust lobes were - not what I expected to find!

Edited by TimZ, 06 November 2010 - 08:31 AM.

[texis30O]

I have a Racer Brown cam, it is very noisy. So much so that I thought something was wrong with the topend of the motor.....It is on a L24 with a Turbo Tom set-up.....I have some youtube videos up if you search "turbo tom"

[Tony D]

Yeah Tim, I know. I'm not going too argue the point, there's just a time when you stop arguing and let people say/believe what they want.

Profile the cam? What's that? It doesn't LOOK like a VW cam, it's got a different ramp coming and going, it must be assymetric. What can you do?

Let them believe what they want.

[TimZ]

Yeah Tim, I know. I'm not going too argue the point, there's just a time when you stop arguing and let people say/believe what they want.

Profile the cam? What's that? It doesn't LOOK like a VW cam, it's got a different ramp coming and going, it must be assymetric. What can you do?

Let them believe what they want.

Okay - WHO ARE YOU AND WHAT HAVE YOU DONE WITH TONY???



...I knew I wasn't telling you anything new - just wanted to throw it out there

Edited by TimZ, 06 November 2010 - 08:30 AM.

[Tony D]

Who is John Galt?

[JMortensen]

Mine were sold to me with the description "snaps the valve open, closes it slowly" and I was told that it would be less likely to float the valves, etc. But I just like to argue no matter what the point is... I was however shown the actual lobe when told it was asymmetric.

Just checked Delta cams website, they advertise asymmetrical lobes as well and describe what makes a cam asymmetric:
http://www.deltacam.com/tech.php

In both engine designs, the rocker arm or lash cap compresses the valve spring to open the valve. As the cam continues to rotate, the force is relieved and the valve closes.Usually, the contour on both sides of the lobe is the same (the contour, or profile, controls the acceleration of the valve). However, if it differs from side to side, the camshaft is said to be asymmetric. The Ford 2300cc engine has asymmetric lobes. If the intake and exhaust lobes have different profiles, the camshaft is referred to as dual pattern design. Some of the so-called "mileage" camshafts are dual pattern.

I think the fact that the open and close rates might be similar is not a defining characteristic of a symmetric cam. The symmetry of the cam relates to the symmetry of the lobe. Maybe the reason that asymmetrical cams work better is because symmetrical cams have asymmetric open and closing characteristics. Certainly would seem to be the case, wouldn't it Tim? If your cam with obviously different ramps has similar lift and closing rates, seems kind of impossible for a cam with symmetrical lobes to do the same, and if the goal of most of these cams is to open the valve faster and close it slower, then a symmetrical cam would open the valve slower and close it faster.

Regardless of any of that, I don't get why anyone would think that Racer Brown should have discovered something in the 70's, this thing would be common knowledge and NOBODY else but Sunbelt would have thought "Hey, that's a pretty good idea! Let's do THAT!" in the intervening 40 years. That strikes me as not likely.

Edited by JMortensen, 06 November 2010 - 09:03 AM.

[dapiper]

I am using that cam now. I have cam card but scanner is on fritz. I can take pix and post as JPG, but as I recall it's a hassle to post. Can someone remind me how?

[Tony D]

"NOBODY else but Sunbelt would have thought "Hey, that's a pretty good idea! Let's do THAT!" in the intervening 40 years. "

Never said that, sometimes your attitude is...poor.
That's the most charitable I can be at this point.

Never said it, you're just plain being an ass misstating it like that.

[TimZ]

Mine were sold to me with the description "snaps the valve open, closes it slowly" and I was told that it would be less likely to float the valves, etc. But I just like to argue no matter what the point is... I was however shown the actual lobe when told it was asymmetric.

Just checked Delta cams website, they advertise asymmetrical lobes as well and describe what makes a cam asymmetric:
http://www.deltacam.com/tech.php


I think the fact that the open and close rates might be similar is not a defining characteristic of a symmetric cam. The symmetry of the cam relates to the symmetry of the lobe. Maybe the reason that asymmetrical cams work better is because symmetrical cams have asymmetric open and closing characteristics. Certainly would seem to be the case, wouldn't it Tim? If your cam with obviously different ramps has similar lift and closing rates, seems kind of impossible for a cam with symmetrical lobes to do the same, and if the goal of most of these cams is to open the valve faster and close it slower, then a symmetrical cam would open the valve slower and close it faster.

Regardless of any of that, I don't get why anyone would think that Racer Brown should have discovered something in the 70's, this thing would be common knowledge and NOBODY else but Sunbelt would have thought "Hey, that's a pretty good idea! Let's do THAT!" in the intervening 40 years. That strikes me as not likely.

This position just doesn't make sense - you are saying that it only matters what the cam lobe looks like, not how it effects the opening and closing of the valves. If you can't tell anything about the performance of the cam by talking about its "symmetry" then there is no point in talking about it at all. You might as well be talking about what font was used to stamp the cam code onto it.

You missed the salient point in the Delta Cams definition -
"Usually, the contour on both sides of the lobe is the same (the contour, or profile, controls the acceleration of the valve)"

...it's the shape of the lobe that results in a given acceleration at the valve that they are referring to, not just the shape of the lobe, devoid of any other information. The "profile" as stated refers to the motion at the valve, not just the visual characteristics of the lobe. So, if the shape of the lobe results in the same valve motion on the opening and closing sides, then it is symmetrical. No other definition is worth talking about.

Edited by TimZ, 07 November 2010 - 07:55 AM.

[CarolinaTZ]

I appreciate you guys chiming in...I definitely learned some things. I'll be installing new stem seals soon and will look more closely at the condition of the cam. In the meantime dapiper (small world, David) has offered to send me the specs on this cam which will help me know what I have. texis30O, I saw your youtube videos...both of them...a year or 2 ago...before I even had this car. Very cool videos...looks like a very nice - and fast - Z you have there! Do you know what cam you have?

Joe

[JMortensen]

This position just doesn't make sense - you are saying that it only matters what the cam lobe looks like, not how it effects the opening and closing of the valves. If you can't tell anything about the performance of the cam by talking about its "symmetry" then there is no point in talking about it at all. You might as well be talking about what font was used to stamp the cam code onto it.

You missed the salient point in the Delta Cams definition -
"Usually, the contour on both sides of the lobe is the same (the contour, or profile, controls the acceleration of the valve)"

...it's the shape of the lobe that results in a given acceleration at the valve that they are referring to, not just the shape of the lobe, devoid of any other information. The "profile" as stated refers to the motion at the valve, not just the visual characteristics of the lobe. So, if the shape of the lobe results in the same valve motion on the opening and closing sides, then it is symmetrical. No other definition is worth talking about.

My position makes perfect sense. The cam lobe is either symmetrical in shape or it is not. If I weren't talking about the cam lobe, and were actually talking about valve speeds or cam timing, I might refer to that as "valve speed symmetry" or "valve timing symmetry" but that is not what people are talking about when they say "asymmetrical camshaft." While your description of valve timing events might be more accurately called "symmetric", that has no bearing on the common meaning of the term asymmetric cam. The common definition refers to the shape of the lobe and the ramps. Some evidence follows. This took about a few minutes to look up on google. You can try and find some that say that asymmetric cam refers to valve speed or valve timing, but based on what I just found I think you'll be looking for a while.

http://www.hotrodder.com/kwkride/cambasic.html
"Asymmetrical - An Asymmetrical cam has opening and closing ramps that are different. These profiles are usually found on high performance cams and offer a high velocity opening and a lower velocity closing ramp in order to snap the valve open quickly and then set it back down more gently. "

http://www.cartechbooks.com/vstore/showdetl.cfm?st=0&st2=0&st3=0&CATID=23&Product_ID=3540&DID=6&chapter=10625
"If you are degreeing a cam with asymmetric cam lobes, you cannot use the lobe centerline method. After precisely setting the degree wheel to TDC as indicated in the text, mark the 0.050-inch timing figures on your degree wheel and verify them with your cam card"
Why can't you use the lobe centerline? Because the lobe isn't symmetrical.

http://www.hotrod.com/techarticles/camshaft_tips_definitions/index.html
"Definition: An asymmetrical camshaft features a lobe shape or profile that is different on the opening side than the closing side of the same lobe. For example, a camshaft could feature a very rapid valve opening profile, but when the valve is closing on the same lobe, the shape could be extremely smooth and gentle."

http://www.tildentechnologies.com/Technical/CamBasics.html
"Asymmetric Lobe - the opening and closing side of the cam are different"

http://books.google.com/books?id=bE111229meQC&pg=PA72&lpg=PA72&dq=asymmetric+cam+lobe&source=bl&ots=g634XxwfPU&sig=siK8162QqdHZJnfz0Fywus2CnkY&hl=en&ei=jU7XTL3HE5CosAO-zrSNCw&sa=X&oi=book_result&ct=result&resnum=2&ved=0CBYQ6AEwATgU#v=onepage&q=asymmetric%20cam%20lobe&f=true

http://www.circletrack.com/techarticles/ctrp_0701_camshaft_design_science/index.html
"An asymmetrical lobe refers to opening and closing ramps that are not identical."

Here's one that even refers to what you and Tony are talking about.
http://www.metricmechanic.com/catalog/dual-profile-asymmetrical-cam.php
"If you look at the BMW intake and exhaust cam lobes, they will appear to be a mirror image of one another and ground with an asymmetrical profile. When you plot out the lift curve on a piece of graph paper, you'll discover that the asymmetrical BMW lobe looks like a symmetrical bell shaped curve. The reason this phenomena occurs is because as the nose of the cam wipes across the curved foot of the rocker arm, the rocker arm ratio changes from a low of 0.9:1 to a high of 1.6:1 (with an average of 1.25:1). So, if we combine a fairly symmetrical lobe with BMW's variable rocker arm ratio we end up generating an asymmetrical cam map."

Is everybody else wrong, or are you and Tony wrong?

[TimZ]

I should have just taken Tony's position.

I'll just say this - from the context of the posts up until mine, it's really clear that everybody (including you, Jon) was talking about the symmetry of the valve opening/closing rates, and assuming that you could tell this by looking at the lobe shape and whether its symmetrical or not. You can't. Not on an L-series cam.

Many other engines do have valvetrain geometry that results in the shape of the lobe being analogous to the valve opening/closing profile, which is most likely why the links posted above made this generalization.

Regardless, trying to help CarolinaTZ ID his cam by telling him it's "asymmetrical" by your definition is pointless. I defy you to find an L-series cam that doesn't have asymmetrical lobes. There are, however, L-series cams that have symmetrical valve opening/closing profiles and those that have asymmetrical valve opening/closing profiles, and that's what everybody in this thread was referring to.

Mine were sold to me with the description "snaps the valve open, closes it slowly" and I was told that it would be less likely to float the valves, etc. But I just like to argue no matter what the point is... I was however shown the actual lobe when told it was asymmetric.