hammertime

iTrader: (1)

Ok, I've read and re-read everything Patrick has said, and I really like the idea of adding power across the board. My requirements differ only slightly, in that my car is not a daily driver. I'm not trying to improve on his setup (how can I?) just trying to tailor my own cam, using what I think I've learned.

IVC near 43-46* for peak power near 6200-6300 & not fighting the LS6 intake (or FAST if I upgrade later)
EVO near 40-45* for longer power stroke, good for torque
I'm shooting for 108 LSA, 108 ICL to make good torque with just a bit more duration overall. So here is what I've come up with:

_______________________________________0.006 __ 0.050 __ 0.200
Intake Duration - ID________________________281 __ 231 __ 156 2128 Lobe
Exhaust Duration - ED______________________277 __ 227 __ 153 2127 Lobe
Lobe Center Angle - LCA (also known as LSA)__108 __ 108 __ 108
Intake Centerline - ICL_____________________108 __ 108 __ 108


Intake Valve opens - IVO____________________32.5 __ 7.5 __ -30 BTDC (- indicates ATDC)
Intake Valve closes - IVC____________________68.5 __ 43.5 __ 6 ABDC
Exhaust Valve Opens - EVO__________________66.5 __ 41.5 __ 4.5 BBDC
Exhaust Valve Closes - EVC__________________30.5 __ 5.5 __ -31.5 ATDC (- indicates BTDC)
Exhaust Centerline - ECL_____________________108 __ 108 __ 108
Overlap____________________________________63 __ 13 __ -61.5 degrees

Because of the narrow lobe separation, it still has 13 degrees overlap at .050. Traditional splits would have 6-8 more degrees of exhaust duration, so that would only add more overlap. Is a cam like this going to make good power across the board and still be able to breathe through a good exhaust system?

:flame suit on: so lets hear what the cam guru's think!

EDIT: I should add, I'm thinking 60cc chambers and .040" Cometics should give a static compression of 11.25:1 and dynamic compression of 8.67:1.

hammertime

iTrader: (1)

Wow - 126 views and not a single reply? Has interest in this idea waned already?

camaroextra

iTrader: (10)

Thats very interesting lol.

No iv been wanting to get a custom grind too, i was thinkg 230's on a 110, but the 108 intrigues me, The more i see it, the tight LSA's are very streetable an are making great driveable power

Patrick G

iTrader: (14)

That cam will make very good mid-range torque and will peak around 6200 rpm. The only potential problem I see is that your overlap is biased a degree or two to the exhaust side of TDC. That means your motor will run out of breath faster after peak power. If you're wanting to keep your shifts below 6800 rpm, then this is a good thing. But if you want to spin your motor to 7000 or above, you'll want to have your overlap biased to the intake side of TDC. The best way to do that is to run the same intake lobe and ICL, but add 8 degrees to the exhaust lobe (giving you a 4 degree forward split).

Good looking cam though!

PREDATOR-Z

0.050
228/230,108/108


6>IVO
42>IVC
43>EVO
7>EVC
108>ECL
13>Overlap*

There ya go

BADFNZ

iTrader: (19)

Patrick, I always see you talk about having the overlap biased on one side or another. How do you determine that? I have the VE calculator but can never figure out where the overlap is biased to.

2c5s

iTrader: (11)

You take the split between adv. duration and divide it by 4. Then subtract any advance.

224/228 +1

4 divide by 4 = 1 - 1 = 0

224/228 + 0

4 divide by 4 = 1 - 0 = 1

Well, that's how it was explained to me.

hammertime

iTrader: (1)

Thanks, Pat. I'll be running the stock bottom end when the time comes, so I think keeping it at 6800 or below would be in my best interest. Even at that point, I'm a bit concerned about the rod bolts.

As for the overlap bias, I'm still not 100% sure I get that 2c5s. Looks like you are subtracting the intake duration from the exhaust at .050", not advertised (not that it usually makes much difference). But how do you read the end result?

Example from cam I proposed...
227-231 = -4
-4/4 = -1
-1 - 0 = -1

Does a negative number reflect exhaust bias, while a positive number shows an intake bias?

Thanks for all the replies.

Patrick G

iTrader: (14)

You can't look at the split between intake and exhaust to see where the cam is making its overlap relative to TDC, you have to look specifically at the EVC and the IVO.

Look at this cam: 224/228 112LSA

When you install the cam straight up with no advance:
IVO 0
IVC 44
EVO 46
EVC 2
This cam has its overlap biased 1 degree to the intake side of TDC (IVO - EVC)/2

Take the same 224/228 cam and install it 4 degrees advanced and you have the following:
IVO 4
IVC 40
EVO 50
EVC -2
This cam has its overlap biased 3 degree to the exhaust side of TDC (IVO - EVC)/2