animuL

iTrader: (3)

I'm down to the last decision before I order a new TSP 408 long block... the cam. My goal is to have something that idles close to stock yet doesn't sacrifice too much on power. The car is a 98 Vette and has complete stock exhaust including manifolds and mufflers. Do you think a TSP Torquer V2 (232/234 .595/.598 on 115LSA) would idle fairly smooth and to the untrained ear seem stock? I know its hardly an apples to apples comparison but I see the stock C6 Zr1 Vettes and that would be an ideal idle for me but I notice while it has similar duration, its got less lift and a lot bigger lsa (211/230 .558/.552 122.5 LSA). I'm a bit worried that having a little smaller engine (408 vs 427) that I may prefer a customized version of the Torquer V2 with greater lsa like 120. What do you guys think? I know I am sacrificing horsepower but I hardly ever race and if I do, there's always nitrous.

Thanks!

Fred Flintstone

iTrader: (1)

pat g is the guy to ask. send him a pm.

animuL

iTrader: (3)

Will do, thanks!

Russ K

iTrader: (1)

I had Geof at EPS spec a Cam Motion 234/242 117+2 .602/.615 cam for my TSP 418. I had a G5X3 114 cam, but I'm tired of the low RPM, light throttle surge and the valve clatter due to the XER lobes.

This new cam will have 4* overlap vs 10* on the G5X3. Also will be quieter due to Geof's lobe design.

But with your stock manifolds/exhaust, I'm sure that you need to have less intake duration and possibly a wider LSA then the TSP cam your talking about. Also I'm sure that TSP uses XER (noisy) lobes.

Russ Kemp

animuL

iTrader: (3)

Any idea what Geofs lobe design is similar to: xe, xfi? Overlap on a torque v2 on 118lsa would be -3* correct?

JakeFusion

iTrader: (7)

EPS lobe is equivalent in power to XE-R (which is above XFI, RPM, HUC, LXL) and a step down from LSL or LSK. It's equivalent in ramp "jerk" to the LXL on the valve open and much less than LSK and LSL and XE-R, and less violent than the XE-R or LSL on the close, but more so than LXL.

JakeFusion

iTrader: (7)

Also, EPS lobes aren't ground on Comp cores anymore. Geoff uses Cam Motion, which is made of a superior alloy with a better heat treating process. The down-side is you pay more for a better camshaft.

animuL

iTrader: (3)

Thanks for that info its helping. Im finding that most stock cams have overlap in the -20* range but its difficult to pin down at what point it becomes lopey. Some say 0* sounds smooth as can be while others say its mild lope.

JakeFusion

iTrader: (7)

Specs of the LS7 cam - this would be like stock in a 408 as well.

211/230 0.591"/0.591" 120 LSA

animuL

iTrader: (3)

I made a little spread sheet that calculates total overlap to help compare with other known setups. https://docs.google.com/spreadsheet/...1SWdSY0E#gid=0

When I change the Torquer V2 to a 118lsa it yields the same overlap as the LS7 which has a nice smooth idle IMO. I know this is really simplified way of looking at cams but based on that I'm thinking it looks like a good choice for my 408.

JakeFusion

iTrader: (7)

LS7 is -19.5

TV2 is -5 at 118 LSA.

Not even close.

Here is the equation: ((Int+Exh)/2)-(2*LSA)

animuL

iTrader: (3)

Hmmm, are you using lift at .050"? I am looking at lift at .004" or .006" in this spread sheet. Data I am getting is coming from image search for TSP cam cards and for GM I'm using this: http://corvetteactioncenter.com/spec...l#.UWhnj6fBM2d

DietCoke

iTrader: (18)

If you don't want lope, get a lingenfelter GT11 and call it a day. Proven camshaft, with negative overlap and great idle characteristics that makes big power

JakeFusion

iTrader: (7)

I am using it at .050. The size at .006 won't tell you much.

JakeFusion

iTrader: (7)

Good suggestion. LPE makes a lot of great stealthy drivers with big cubes.

animuL

iTrader: (3)

Interesting, I was told the exact opposite: that idle quality depends a lot on what happens from .004 or .005 to .050. I'm starting to plug in the values for .050 and seeing big differences. Would this have to do with ramp rates / lobe profiles?

JakeFusion

iTrader: (7)

I've been told that too. But that matters when looking at various lobes. Say a 224/228 cam... one has super aggressive ramp rates - it'll idle better than one with lazy lobes.

Same can be said if you have lazy lobes on the 224/228 and aggressive lobeso n the 230/232 - maybe the 230 idles about the same. But the problem is you spend so little time just off the seat @ .006", you have to look at .050" duration and really even .200" duration too to get a picture for overall idle/drivability quality.

animuL

iTrader: (3)

When we are saying duration at .006 and .050 we are talking duration from when the valve is opened .006 or .050 until when it is .006 or .050 from being closed right? So you spend more time going from .006 to .006 than from .050 to .050. Not trying to question you really just trying to understand.

animuL

iTrader: (3)

BTW, I am ordering a long block from TSP so thats why I am so fixiated on their cams.

I updated my spread sheet: https://docs.google.com/spreadsheet/...1SWdSY0E#gid=0

I put my MS3 that in my Camaro for reference because I know what it sounds like and its too much for me... now I see why.

comparing overlap at two different heights I figure the cam I want will have larger duration at .050 than other options, yet lower overlap. The cam that seems to stick out is the 228R at 118lsa. It has more duration and lots more lift than stock hi-hp LS cams yet overlap is not nearly as much as some of the big cams. Maybe lose 5-10 hp over the Torquer V2??

JakeFusion

iTrader: (7)

Overlap is power at the expense of everything else.

Now for your other question, the way I understand it is this:

The duration numbers @ .00x" is not valve lift. It is lobe lift. The lifter starts to ride the cam lobe and where it begins to open the valve is around .006" or so of cam lobe lift. At .050" of cam lobe you have less duration. This is how you get ramp rate in degrees. It is more duration at .006" and less at .050 and even less at .200" - look at a cam and you see why. The lobe becomes smaller as you move away from the cam core. When you look at "square lobes" you can see why they are aggressive. They come off fast and don't fall off much. Solid rollers are like this. Overlap at .050" gives you a pretty good idea of the median overlap for the entire profile.

Now, what is overlap exactly? Overlap is the "5th" cycle in the power stroke where the intake and exhaust valve are open at the same time, thus allowing the exhaust pulse to suck in fresh air for greater volumetric efficiency. This is why it makes more power with higher RPMs. It helps keep the air coming in. At lower RPMs, you have a problem of unburnt fuel and partial cylinder filling due to the low vacuum that the valves hanging open causes. You don't build enough cylinder pressure for decent driving, torque, or brake boost. This is why high overlap cams need more compression also. And that's a function of the intake valve closing point and installed centerline. Usually, big cams with lots of overlap "bleed" off compression or really, they just don't create enough cylinder pressure because the valves hang open longer. ICL plays a part in this, but the rule of thumb is, more compression with more overlap to keep cylinder pressures up for drivability, torque, and brake boost.