JMortensen

"We're gettin nowhere mighty fast, Cap'n!"

My points were that the computer does make it easier to design a cam, and that the bolded companies on the list make cams for L series and also own a machine which lets them easily check valve timing and valve speeds right at the valve, so they could easily make the changes necessary to get asymmetric valve timing if they didn't already have it on their stolen cam profiles. ISKY was not on the company's list. Maybe they use slide rules, but I doubt it. They're probably using some other software. For the last time, I think it's unlikely that every company that makes a cam with an asymmetric lobe and sells it as "opens quick closes soft" would have had one attempt at stealing someone else's design and then never bothered to update since the 1970s, especially since all of this technology has become available. With the knowledge that 6 of the common suppliers (common enough that I recognize their names from the list) have the technology to easily understand the effect of changes to the lobe shape at the valve, I just don't see them all sitting around trying to keep selling the cam profiles that they stole 40 years ago. I have no idea why you are so dead set on the notion that nearly all cam manufacturers are thieving morons, but I do not share your analysis, and I think the fact that they are buying this technology supports my argument. CarolinaTZ, I'm glad you got your cam identified.

Pretty simple test there... switch them and see if it's loose.

Read my last post again. The list has nothing to do with cam asymmetry.

Get a pyrometer and reinstall the bar. You can pull one end link at the track between sessions to see the difference with and without the bar. Without tire temps all we can give is relatively vague suggestions. EDIT--I do see that you have different struts front and rear. I can't imagine that being a good thing, especially since the Konis aren't really the "race" version.

I've conclusively proven you wrong about cam asymmetry. Do I now need to show you how cam manufacturing might have changed since 1980? Can you really not come up with the one tool that I'd bet $1000 that every cam manufacturer has in their shop which would make cam design a whole lot easier? I'll give you a hint. You're sitting at one. Again, took 2 minutes to search "camshaft design software" this link has 4 different suggestions for software http://www.eng-tips....d=163889&page=4 This one looks to be for large businesses. http://www.designofmachinery.com/Cam/ And here is a machine that can (among other things) measure the lift and duration of the cam at the valve on the engine. http://www.audietech...m-pro-plus.html EDIT- Here is a list of companies using this machine, I've bolded the ones which from memory make L series cams. There very well might be more: Bordeaux Dyno Cams Boubis Cams Brian Crower, Inc. Bullet Racing Cams Cam Motion Cam Tech - Australia Camcraft Performance Cams Camshaft Engineering Co. Camshaft Machine Colt Cams Crane Cams Crower Cams Demos Cams Dougherty Racing Cams Elgin Cams Erson Cams ESTAS - Germany Howards Cams Huggins Cams Hyperformance Camshaft Integral Cams Kent Cams - England Kelford Cams - New Zealand Kiwi Cams Ltd. Lunati Cams Megacycle Cams Precision Cams Schneider Racing Cams Spiros Cams Sure Cam Universal Crankshaft Wade Camshaft Web Cam I don't know what you've convinced yourself of regarding people and their relative stupidity as compared to you (although I've got a pretty good idea), but I'm convinced that there are a large number of people out there pursuing speed, and ones that get really serious about it will use their brains and sometimes their engineering degrees to much greater effect than you seem to want to give them credit for. In the meantime, I've got just a few minutes into proving my point about asymmetry, and just a couple more into showing how all those troglodytes that you show so much disdain for might have managed to figure out a little bit more about cam design than you're giving them credit for. If you're going to come back to this argument again, can you please provide some actual proof of something?

Glad we cleared that up.

People who use the term "symmetric cam" are talking first and foremost about the shape of the lobe, I think that is clear based on the links I posted. You're partially right though Tim. I assumed that the shape of the lift curves when plotted would be roughly analogous to the shape of the lobe. So when I said I had two cams that were asymmetric, I made that distinction based on the shape of the lobe, because "everyone knows how to tell an asymmetric cam". I learned something about my erroneous assumption about how the cams really act from your post and I appreciate the education. Regardless, the cam that acts like we are all describing with regards to timing is still going to have an asymmetric profile, with a fast lift ramp and a slow close ramp. Tony's assumption that Delta, Sunbelt, and Isky make asymmetrically timed cams for the L series and "others" use "old tech bumpstick profile" still strikes me as wrong and if I were one of those "other" cam manufacturers I'd be insulted by it. As you pointed out Tim, virtually every cam that you can find for an L series is asymmetrical. Don't you think it would be a strange thing to assume that every cam manufacturer had gone through and found the proper profile to get equal timing events on the open and close of the valve, and then make all of their cams a variation of that basic profile to maintain their symmetry, especially while simultaneously advertising that their asymmetric cam profile opens the valve quickly and closes it slowly? Are they all liars, or are they all too stupid to figure it out, while simultaneously being smart enough to ensure the symmetry of all of their L cams? No customer with a race car ever plotted it out and came back and said: "Hey, this thing actually opens and closes pretty evenly"? And no cam manufacturer ever cared enough to put their cam in a car with a degree wheel and a dial indicator and check what the thing actually does on the engine and then thought to himself: "Hey, what if we modified this thing to actually open the valve quickly and close it slowly, in the same way that works with our cars that don't have the curved rocker contact surface throwing the cam timing off?" None of those cam grinders ever put it through a computer model? Really? I dunno. It seems like you have to have an awfully low estimate of a lot of peoples' integrity or intelligence to believe such a thing.

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?

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.

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

Bad math. You know it's bad when I correct it...

Maybe I'm reading it wrong. 114.3 - 114 = .3 mm 1mm = .040, so .3 mm is .012. Halve that and you're going to be out of center by .006" on each lug nut. I wouldn't think that would be so prone to failure. My inclination is that if someone is listing 4x114 wheels they're just being lazy and not putting the .3 on the end.

Would guess that the holes were there to finish welding the halo to the main hoop. Again John, very very nice. Can't wait to hear about the first track day.

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...

Wow, and I thought mine was going to be bad...

Been emailing some more with Glenn, and I think what would help is a look at the rear of his car. It has a HUGE diffuser on it and apparently a full undertray as well. He was a bit confused about what I was asking, but we finally worked it out. He ended up saying: "Dont put the [airdam] on the splitter, unless you are only interested in an air dam and are willing to forget about the downforce of that tray and the splitter." This makes perfect sense. You need air to the diffuser, so if you're running a diffuser, then an airdam isn't helping. Still leaves me wondering what to do since I can't run an undertray for autox but have no rules to follow for track days... He also said that they changed so much stuff on the car that the driver was having a hard time getting the most out of it. He thought they had another 3 seconds per lap in there but they broke in the first session after only 3 laps and still won outright. Impressive.

110V Mig, 60 gal 220V compressor, cheap ass metal band saw, nearly useless drill press, 12 ton press, and a cheap belt/disk sander about sums up my fabrication equipment. The one I regret is a 1 hp 3/4" chuck 20" drill press that I bought from a factory that was closing down in CA and it was about 350 lbs, so I didn't move it up to CA. I gave it to a buddy and he still has it, then I moved up here and actually started fabricating parts, so now that I could actually use it I no longer have it. Bought it for $150, would probably spend $500+ to replace it. Water under the bridge I guess, at least it went to a good home. My friend is far more mechanically inclined than I am and I owed him big time.

Emailed Mr. Bunch and got a long response. Here is the meat with regards to the airdam/spoiler combo: So it looks like he thinks it's better without.

Looks like the car that was fastest in the UTCC has my splitter on it. It's that crazy fast Hemi Challenger: http://grassrootsmot...m/utcc/updates/

There you go. And the 4 speeds came with 3.36 or 3.54 gearing, the T5 came with 3.54, and the 280ZX came with 3.90. If you have to shift to 3rd in the 4 speed, the T5, or the early 5 speed, you're going to lose time not only because of the shift but also because the 2nd to 3rd gap is so big relative to the close ratio transmissions. If I were choosing between the 4 speed and the T5 I'd go with the 4 speed. I believe it is lighter and the shifter is better. Might be that you can get a better shifter for the T5, dunno about that.

Not all of them. In fact very few of them are LSD. Do a search, read my sticky in this forum you'll find what you need.

The easier move is to buy a 3.54 or 3.36 (rare) rear end and swap the LSD into it. I've done a writeup on it and it's in the FAQ section. Very simple compared to swapping gears.

That spring recommendation sounds familiar. The machinist I used warned that some aftermarket springs were WAY too stiff, I can't recall if he was worried about Crane or ISKY, but I told him I had already ordered springs and he had me all set to return them. He checked the Schneiders on his spring dyno and told me they were just about perfect for what he liked in terms of seat pressure and installed them. Slover and Gerolamy were the two names I heard most when it came to porting Datsun heads. I came into Datsuns through 510 guys, and those two shops were kind of mythical. Rebello as well, but I heard about Slover and Gerolamy first.

I hate the wide gears on the T5 and the Nissan 4 speeds, and went with a 280ZX box from 1980 which has a slightly closer 5th than the later 81-83, and has tighter 1-4 ratios than the 76 or 77 up to 79 (yes, 1st year of ZX too) transmissions. Don't change the trans and forget about the diff though. The close ratio transmission really requires that you have a fairly low rear end ratio. 3.9 or lower preferably. The really serious guys like the comp boxes. The less shifting you have to do the better. If you can shift it into second and hit the top speed you expect (say 70 mph) that is probably the best you can do. Basically get off the line, shift to 2nd, and forget about shifting. Left foot stays on the brake, right on the gas, and you 're good to go until the end of the run. You can use a calculator like the one below to figure it all out: http://webspace.webring.com/people/cz/z_design_studio/