freddyvette

Hey lamboworld,

Here's my cam.


and this is the dyno with very long stock pushrods, since been corrected. no re-dyno yet.



im interested to see what people have to say about my cam. I'm not really sure where it stands. would people recommend moving to a different cam?

lambo, I saw your cammotion cam that you have is listed for 1.7 rocker ratio. I'd give cammotion a call and see what they say about that cam for a 1.8 ratio application. as you can see yours is very similar to mine with a little bit different duration.

driveability is kind of shitty, but then again I'm super sensitive to bucking and lugging. I dont like those noises coming from my car.

thoughts? would love to hear them.

here are my other mods:

LS7 SDPC Short block
blueprinted (933 deck 54 quench)
Mahle -3cc pistons
Manley rods
Manley crank
4.130 bore
LME heads
LS7 lifters with 7.725 BTR pushrods
Ferrea hollow steel exh valve, stock intake
660 lift BTR springs with correct install height
Comp rocker bearing kit
ATI stock size balancer
Corsa cold air intake
MAMO MSD intake
Lightly ported LS7 TB
TSP 1 3/4 exhaust, catless midpipe
stock catbacks
Mantic twin disk
93 pump gas (daily driver)

Apocolipse

I like your cam...but it sure sinks up top quick which makes me wonder if something is up with your valvetrain stability.

freddyvette

Yes, that dyno was taken last year when it had stock pushrods that were way off. I have since replaced them to obtain about .080" preload.

Apocolipse

Ah okay - they were off as in too much preload or not enough?

barum

I make them myself. Yes, there are online calculators, but they are a bit reduced for my needs.

lamboworld

freddyvette

Way too much, which I heard can cause excessive lift that reduces controllability at higher RPM

I was referring to your post # 3 in this thread, it shows 1.7 rockers and less lift due to the lower ratio. The one I posted was specified for an LS7 to the manufacturer (cammotion) and thus different ramping lobes were used.

I was told by their engineering department that the ramps are steeper with a shorter base circle for an LS7 with a larger volume intake runner and combusion chamber.

barum

I've seen tests where smaller preload increases low end torque/power but loses on top and vice versa => higher preload increases top end torque/power, but loses down low. I try to aim to 0.100" preload with LSx hydraulic lifters.

As someone commented your dyno sheet, it looks a lot like stability issue which could indicate other dimensioning issues than just push rod length (like too little safety margin with spring rates or some nominal frequency issues).
This is interesting, it's the first time I've heard steeper ramps being selected just on the basis of an engine being LS7.

I theory when everything except the rocker ratio is kept the same, 1.8 ratio will have more spring force reserve than 1.7 ratio. Naturally the rocker inertia will be higher with 1.8 ratio assuming similar dimensioning, so in practice the difference will neglible.

However, LS7 valve guides are notorious of wearing out more rapidly than other oem designs, which is why it is highly advisable to use smoother ramps, at least if no roller rockers are utilized at the same time.

I'm having one 1.8 ratio Cam Motion cam "cam doctored" right now and will be comparing it to Comp LXL profiles with almost identical durations/lift. Will be interesting.

lamboworld

If you use the lift numbers on my cam card it works out to .650"/.652" with 1.8 Rockers. I spec'd this cam myself and Cam Motion knew that it was going in an LS7 with 1.8 rockers. I have talked to them many times and they have never mentioned to me that they are using different lobes on the LS7.

Here are the specific number that I gave them:

Spec Your Own Camshaft
(Intake Duration @ .050: 238, Intake Valve Lift: .650, Rocker Ratio Intake: 1.8, Exhaust Duration @ .050: 252, Exhaust Valve Lift: .652, Rocker Ratio Exhaust: 1.8, Lobe Separation: 114, Camshaft Advance: +3, Roller Lifter Wheel Diameter: .70, Options: Hydraulic, Induction Type: Naturally Aspirated, Camshaft Core Types: 3-Bolt, 8620 Steel Alloy Camshaft $449.00)


Lastly, my car is being finished today and I should have some results. My tuner has been street tuning it for drivability and he said that it drives great with hardly no surging. It has been very hot in NC and I am not sure how that will impact the dyno numbers. My tuner said that it was 97 in the dyno room at 11am yesterday and it is supposed to be just as hot today. I guess that the numbers will correct for the heat and humidity.

freddyvette

Ooh sounds like you're getting close. I have an itch to go out to tail of the dragon. Maybe we can find a stretch and compare? (i'm in hotlanta)