asymmetrical vs symmetrical cams on L28

[turbogrill]

Hi,

 

Any one have any clues? 

Will an asymmetrical benefit when the exhaust is restricted such as not having headers?

I suspect there is more to it than that.

 

(I refer a asymmetrical cam as being exhaust duration differs from intake duration.)

 

 

I am comparing these cams Schneider cams (click the image for full size):

 

 

  

 

Engine is Megasquirted L28, headers and N47 head. (Stock 8.3 comp)

 

It's for a racer so really don't care about <3000 RPM.

 

I have been trying to figure out how important a symmetrical vs asymmetrical cam is for the L28 engines, google doesn't give much.

Edited August 26, 2016 by turbogrill

[Tony D]

Asymmetrical Cams refer to how the ramps are ground. 

Please change your title and terminology to 'Split-Duration' which is what you are asking about.

 

Split Duration Cams are very good at what they do. Look up "Split Duration Cams" and not Asymetric" and you should find a lot more out that what your original parameters  were.... For a 'racer' there are advantages for torque...Serious Racers will have a cam cut for their engine, it doesn't cost any more and the advantages are manyfold. 

 

Power is in the Head. Always has been. Get induction and cam right and you're golden. Don't just buy off the shelf.

[Brad-ManQ45]

I may be wr9ng and if so I'm sure TonyD or someone else will correct me - but I believe the stock cams ARE assymetrical...

[WhitleyTune]

Generally speaking, more exhaust duration is going to lose you some torque under the peak and move it to above the peak. What are your full engine specs and your racing class? Whether you run more exhaust duration depends entirely on the engines intended use and level of modification. Or are you just after some general cam spec knowledge? 

 

Modern valve lift profile design means we can optimize valve event time-area without needing to increase duration though, so a modern design might act like a dual pattern without you having any idea from the basic cams specs like the ones you have shown.  

 

Historically, aftermarket cam grinders have used dual pattern cams for years. With old cam design it was easier to stretch the duration of a master-plate profile to increase time-area than producing a complete new profile. That's why you see most L series cams are dual pattern, it is old tech, metal master plates and manual ground cams. Not saying they are bad or won't make power, but there are definite improvements with modern designs and manufacturing. 

 

The L series, like any other motor, responds well to proper valve event timing. The stock L28 cam is a turd and has no overlap. Its been a while since I cam doctored one but If they are dual pattern, its small and not going to alter performance to any great deal. The problem with the shelf aftermarket cams is they aren't wide ranged enough to really suit all the motors that are out there.  I will be offering new L series camshaft designs in the near future, CNC ground to any specification required. 

Edited August 29, 2016 by WhitleyTune

[turbogrill]

Hi,

 

Thank you for the information and the clarification of the lingo!

Could you say that a dual cam profile might give you a more "exptionential" power curve compared to a little more linear power curve from single cams?

So a dual cam might have higher peak but lower avg hp?

 

Example (taken out of the blue):

- Dual profile. Avg HP 3000-6000 RPM: 190, Peak HP: 260

- Single profile. Avg HP 3000-6000 RPM: 220, Peak HP: 240

 

Generally speaking, more exhaust duration is going to lose you some torque under the peak and move it to above the peak. What are your full engine specs and your racing class? Whether you run more exhaust duration depends entirely on the engines intended use and level of modification. Or are you just after some general cam spec knowledge?

Given my requirements are road racing, 3000-7000 RPM. What specs determines what cam to use and how? Is it compression? Head flow? Headers? Fuel delivery?

[Tony D]

Yes