Another cam thread.
10-02-2012 | 10:45 AM
#41
Nealy any place will do custom grinds. I also kind of disagree with the notion that a lower LSA will provide more low end torque as a general statement. What a lower LSA does is it changes the powerband from a plateau shape to a mountain shape with the peak numbers coming in lower than the "peak" of the higher LSA. If you're talking about moving the curve down to a lower RPM range uniformly, then you're talking advance. Lower LSAs also come with lower vacuum and typically higher overlap which comes with it's own emissions implications.
Here is a good read about the effects of LSA's. A lower LSA will definitely feel much more snappy at lower rpms. That is why LS9 cam guys complain about the soggy low end. Yes, the LS9 cam will idle like a dream and pull some serious vacuum but I wouldn't want that cam with a stock stall. It is just a balancing act like all the other parts in your combo.
10-02-2012 | 03:25 PM
#42
Staging Lane
Joined: Sep 2012
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TECH AND TUNING TIPS QUESTIONS AND ANSWERS CALL 407
If a cam has a 1400 - 5500 with a 116 LSA, then the 112 LSA will likely be something like 1400-5200, but will peak higher and peak at a lower RPM. To move the entire powerband down you need to advance the timing. Cylinder pressure through means of aggressive ramp and lift play a much bigger part in total gains. Like you said, the balance between lift, duration, advance and LSA are all important factors but people tend to look too much at LSA and make an assessment. A short duration, high lift cam with fairly aggressive ramp rates will build more torque and will also be peakier from the start. Narrowing the LSA will make the power even peakier and in increasing overlap, you will hurt idle quality, vacuum and make it more difficult to pass emissions. Again, a good tune will help with all of this. Anything lower than a 113 LSA is a little low for my personal tastes on a high lift short duration cam for a daily driver.
Lobe Separation - Lobe separation is the distance in camshaft degrees that the intake and exhaust lobe centerlines are spread apart. This separation changes cylinder pressure and determines where peak torque will occur within the engine’s RPM and power range. Tight lobe separations, such as 106°/108° or shorter, will increase cylinder pressure, causing peak torque to build earlier in the RPM range and peak-out in a short amount of time. This is great for dirt track racing, so the car comes out of the corner hard. The shorter lobe separation will also give that rough idle everyone loves to hear. A broader lobe separation, such as 112°/114° or wider, will reduce cylinder pressure. This causes the torque peak to come in later in the RPM range, but also allows the torque to build over a wider RPM range, giving you more mid-range and top-end power. This type of lobe separation is needed in many applications, such as fuel injected, nitrous and blower applications. Broader separation angles produce increased idle vacuum for more stable, cleaner, idles and better low end performance. They allow for easier tuning, as well.
10-02-2012 | 03:40 PM
#43
Teching In
Joined: Mar 2012
Posts: 28
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Attached below is a picture of what I would tow on a regular basis. It was a 21ft sea devil. My tranny temps hit 205 degrees last summer because we had the bed loaded with weekend gear and there was four people inside the truck. My stage 3 pro series TC drove like stock until I hammered down on it. I used my truck and never had any issues with towing or racing. However, I still say install the TC first, then regear. Add the cam later on when you can afford pushrods, valve strings, etc.
Last edited by tcr0148; 10-03-2012 at 11:09 AM.
10-02-2012 | 04:49 PM
#44
Don't know where you are getting the overlap argument from. A 212/218 cam wouldn't have overlap until around a 107 lsa. I only see benefits from running an LSA around 112 degrees in a towing application. But that is just me.
10-02-2012 | 05:37 PM
#45
Staging Lane
Joined: Sep 2012
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There is overlap on nearly every cam, but it happens to be negative on most modern vehicles with emissions regulations. While not exact, (((intake + exhaust)/4)-LSA)*2 or (Intake+Exhaust)/2-(2xLSA) will get you close. I can't remember off the top of my head, but -4* overlap is about as much as you can go and still pass a sniffer with a PERFECT tune. I prefer to stay a little higher to keep me safe. The stock LM7 cam with a 191/190 114 has -37.5 overlap and a reverse split so it is way over-conservative for a sniffer that is looking for unburnt fuel. Negative overlap is also better with part-throttle efficiency.
10-08-2012 | 08:19 AM
#47
Staging Lane
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I am not too sure about the 799 springs, but the most commonly recommended are PAC 1218 or Comp 918 (comps less so because of some breakages). With a low lift 212/218 I'd personally stick with LS6 springs. The 212/218 or comparable is the most commonly recommended truck cam so no complaints there.
10-23-2012 | 12:00 AM
#48
i have a 212/218 high lift on 112+2 in my cc and it actually does really well as a dd and roll racer, havent taken to track yet but all in all i love it may throw in a 2600 converter for ***** and giggles but who knows.
