LS7 CAM HELP

[erikgunnar]

Dear Cam Gurus!

I have an LS7 engine today with a hydraulic cam 224/0.661 - 246/0.661 113+4. Overlap 9. 13:8 compression and E85.
Peak HP 624hp at 6550RPM

I will go to a Low Lash solid roller and no more overlap than todays 9.

Below are two cam options both with 9 overlap. Note that numbers below are HYD numbers. Low Lash numbers will be +6.

CAM 1
226/7.20 - 244/7.05 113+2

CAM 2
230/7.20 - 252/7.05 116+5

So my question 1

How will above cam differ from each other when it comes to:

• Max Power
• Peak Power rpm
• Torque Curve characteristic


Question 2

I read a lot regarding different LSA and there are plenty of shoot out tests showing how different LSA change the power and torque curve. But they all run tests by keeping duration the same on all cams and changing the LSA. Of course engine characters will change when you change overlap.

But can some one explain if I have two cams:

Identical lift
Identical overlap
One has shorter durations and tight LSA
One has longer durations and a wide LSA

What will be the difference on a 4.00 stroke 427 engine?

Many thanks in advance.

[wyrmrider]

Graph the lift curves minus the lash
have you upgraded your rockers
any work on the heads
do you have the Intensities of the two cams duration from .020 to .050
any changes to FI?

[erikgunnar]

Thanks.

Sorry I do not have the lobe info you ask me about. The two cams I put down was to be done by Cammotion. I have T&D shaft rockers and fully ported heads with out stall.

But in general what can we say about increasing the durations and widening LSA compared to shorter durations and more narrow LSA. Overlap kept the same.

I do not seem to find any info on that topic. Maybe only me asking this.

[CamKing]

You do not design a cam, around overlap. Overlap is nothing but a result of the duration and centerlines. It's the last thing you worry about.

As for your question, the cam with the shorter duration, and tighter LSA will make peak HP and peak torque, at a lower RPM, the torque curve will be peakier, and the power will fall off sooner.

[wyrmrider]

If you have head flows could you post them up
you need to start with piston demand (where it is and how it's pulling on the intake, your heads and how they match demand
your valve curtain for low lifts, your rocker ratios (what are they) then your cam events are plotted and as Mike said your overlap is a result- an output not an input
ah- usage and all the details like headers, gearing are also critical
picking a cam out of a catalogue does not work out unless you want to test several (or in my case many)

[erikgunnar]

HEAD FLOW

From 0,1 to 0,8
70-139-216-278-325-362-362-362

1.8 lifters

33 inch long headers 1.75

Gearing 3.91

Attached is the dyno with the 224/0.661 - 246/0.661 113+4 cam

Dyno C6 Z06.jpeg

[CGT]

HEAD FLOW

From 0,1 to 0,8
70-139-216-278-325-362-362-362

1.8 lifters

33 inch long headers 1.75

Gearing 3.91

Attached is the dyno with the 224/0.661 - 246/0.661 113+4 cam

Dyno C6 Z06.jpeg

That's a stout ls7 combo as is. I agree that you don't design a camshaft around overlap. Cam 1 would be shutting the intake valve(ivc) several degrees sooner than the stock LS7 CAM. 211-230 121. Cam 2 in about the same place as the stock cam. I would think your combo would favor a little bit later IVC. I think the valve events of cam 2 would be overall more favorable for your deal. Of the two, I would choose cam 2.

[erikgunnar]

Thanks for your input.

Could I increase overlap on cam 2 and still not get more bucking/revision compared to current cam?

Any one else?

[wyrmrider]

Hi
glad you are taking an interest in the details instead of calling some cam help line
First it's nice to know where the stock and current intake close- you don't start building compression till the intake closes completely- which is why I asked about .006 .050 does not get it close enough

you can only compare those two cams if they are of the same cam family from the specs given. (without plotting them or a Cam DOC)

if, for example
The shorter one was a really fast acting drag cam (short intensity number) and the longer one was a slower acting endurance cam the short one might act "bigger" in the engine and have more effective overlap and idle rougher, more reversion etc
example two
if the shorter one had Mike Jones inverse radius profiles it might act longer than the longer one
by more degrees than you are comparing in your examples
Bottom line is that .050 is a really gross measurement even if you adjust for lash (or 0 lash hyd)
so where in the rpm band do you want MORE
where are the HYD coming up short- plenty of threads here on ST about different oils
Not knowing what you are doing there is a big difference in what cam you want for a WOT (only) drag cam like for A COPO
and a cam that has to work at part throttle and off corners
1.8 lifters- that makes it easier
now to get a cam that waits to open as late as possible on the intake and close as early and easily as possible on the exhaust
one that closes when the last little bit of ram air velocity is moving through the intake valve as the piston is coming up after BDC one that opens the exhaust as late as possible to get the most power out while still blowing down the cylinder pressure before the piston starts up
lots of things for the camgrinder to consider and as you say you do not want the intake flowing in not backward or the exhaust flowing into the intake I take it you want this vehicle driveable

[CGT]

Thanks for your input.

Could I increase overlap on cam 2 and still not get more bucking/revision compared to current cam?

Any one else?

E38 PCM I assume? Very tuneable, yet, they all can only be "so good" as far as driveability. There are a lot of variables going into driveabilty, and alot of people tolerate different levels of hiccups. But I personally would think that any of the cams listed, could be made to drive well with that PCM.

[wyrmrider]

from another thread
"We install a cam like 234/244 @ .050" in a pretty healthy 10:1 engine with decent heads and intake 400 + hp engine."
Is this the camshaft you are referring to? (234-244 @.050" 112LSA .488"-.510" valve lift) ?
I had a mid 9:1 355 idle fine at 800 rpm on stock converter with a 230/236 113 lsa cam, hyd roller but was an efi car.
experts answer was
If your 234/244 @.050", is 292/296 @.006",
than my 234/242 @.050" 280/288 @.006"

notice that the same intake duration @.050 and 12 degrees shorter at .006
if we assume that the LCAs are the same (and you have 8 degrees different on the exhaust lobe)
or if we split the difference Mike's shorter seat duration cam has 10 degrees less overlap at .006 eventhough the .050's are about the same
now this is not exactly accurate with different intake and exhaust profiles and asymetrical lobes but you get the idea
provide the info for both of these as appropriate
http://jonescams.com/road-race/
http://jonescams.com/street-performance/
and let's see what he comes up with

[erikgunnar]

Thanks for a great input.

I use the car for 40% daily driver, 60% track days and 10% drag racing.

With the current cam and 3.42 gearing it did 10:80sec. Will change to 3.90 gearing.

WHERE I AM NOW:
I have the HYD cam and 1:8 rockers

at 0.50 = 224/0.661 - 246/0.661 113+4 cam
At 0,004 = 280 and 303
At 0.200 = 149 and 167

Performance as per dyno chart.
The cam is on the limit for me with bucking/revision up to 1600rpm. I can drive it on 6 gear from 1000 rpm when i load it but in first/second gear on super light load it does buck. No tuning can change it so pls do not advice this. Please.

WHERE I WANT TO GO:
I want a Low Lash Solid Roller ( who can make it apart from Cammotion?) and I have 1:8 shaft rockers and solid roller lifters set.

I want the max cam I can have but still no more bucking or revision compared to current cam.
Has to work with my ported OEM LS7 heads. 13:8 comp and E85

I am thinking that the real advantage by going solid is lift and rev. So I feel that is what to use to get me to the next level. Lift and rev!

My suggestions was the 2 cams i presented but you guys probably have great ideas that can make me chose a better cam.

Please bring it on!

Many thanks in advance.

[CGT]

http://www.compcams.com/Technical/Catal ... atalog.pdf

I believe the LSA and LSB lobe profiles would be good choices.

[ptuomov]

Dumb question, but are individual throttle bodies an option, if the car currently has a plenum manifold?

[statsystems]

Thanks for a great input.

I use the car for 40% daily driver, 60% track days and 10% drag racing.

With the current cam and 3.42 gearing it did 10:80sec. Will change to 3.90 gearing.

WHERE I AM NOW:
I have the HYD cam and 1:8 rockers

at 0.50 = 224/0.661 - 246/0.661 113+4 cam
At 0,004 = 280 and 303
At 0.200 = 149 and 167

Performance as per dyno chart.
The cam is on the limit for me with bucking/revision up to 1600rpm. I can drive it on 6 gear from 1000 rpm when i load it but in first/second gear on super light load it does buck. No tuning can change it so pls do not advice this. Please.

WHERE I WANT TO GO:
I want a Low Lash Solid Roller ( who can make it apart from Cammotion?) and I have 1:8 shaft rockers and solid roller lifters set.

I want the max cam I can have but still no more bucking or revision compared to current cam.
Has to work with my ported OEM LS7 heads. 13:8 comp and E85

I am thinking that the real advantage by going solid is lift and rev. So I feel that is what to use to get me to the next level. Lift and rev!

My suggestions was the 2 cams i presented but you guys probably have great ideas that can make me chose a better cam.

Please bring it on!

Many thanks in advance.

That change in gearing all by itself will help with the bucking.