Cams for superchargers

[CaysE]

Surely this has got to be the best place on the Internet to ask this question. :beer:

I have an SVT Focus which is getting a Jackson SC installed. Stiegemeier will be porting and rebuilding it, and I have a ported head, high flow cat and 3" exhaust. Stock valves, stock bottom end. I don't know much about cam profiles though and will need a custom grind.

If I understand things right, n/a cams have some overlap to help evacuate exhaust gasses, but you want less overlap with an s/c. Is this correct? What should I be aiming for, in general?

 

[AntiHeightPunk]

modular powerhouse makes custom cams, if your gettinv custom cams call them and talk to them

 

[hammerhead2]

Normally speaking yes N/A cams will have more overlap. The blower cams tend to have about 8-14 degrees more exhaust duration than intake and usually range from 112-116 on lobe seperation, depending on motor setup, blower type, boost ect. The reason you see less overlap on FI motors is to avoid bleeding off boost.

 

[sn95leen]

Surely this has got to be the best place on the Internet to ask this question. :beer:

Wrong. Other than being able to provide recommendations on who can grind a cam for you, no one on here is really gonna know enough to give you anything more than a "guess" as to what cam to look into. There may be a handful @ best, but I have yet to see any on here.

If I understand things right, n/a cams have some overlap to help evacuate exhaust gasses, but you want less overlap with an s/c. Is this correct? What should I be aiming for, in general?

You won't be able to understand what to aim for overnight, or by the time you've found a custom grinder and he's ground your profile ... leave it up to your custom grinder, they're really the only person who won't be guessing for specs.

Good luck.

 

[meaty mac]

Normally speaking yes N/A cams will have more overlap. The blower cams tend to have about 8-14 degrees more exhaust duration than intake and usually range from 112-116 on lobe seperation, depending on motor setup, blower type, boost ect. The reason you see less overlap on FI motors is to avoid bleeding off boost.

Good post.
I will add that the intended purpose is relevant.
On a street driven 4V, an intake centerline of say 117 degrees may be used to keep the overlap reasonable for improved idle.
Race cars would change the centerline for more top end power.
Your best bet would be to check out the bigger cam makers out there as i dont think that you'll have to go the custom route. good luck :beer:

 

[CaysE]

Not looking to learn overnight; just looking to learn.

Can someone explain lobe separation?

 

[69gt4speed]

Look here it is the degrees from top of intake cam to top of exhaust cam. It's fixed on a ohv or sohc engine by the cam grinder. On a dohc you can by using adj. sprockets or pulleys adj. the seperation degrees. With stock sprockets or pulleys might be able to file the keys a lil if they use bolts to actually hold the cam to sprocket or pulley. Otherwise again the cam grinder can grind the angle you want. On a dohc v6 or v8 it sometimes needs to be exactly phased in the same, bank to bank also. As you see the wider the angle or more degrees the less overlap w same lobe duration.

adj. sprockets/pulleys for a focus
http://www.turbozx3.com/images/FC-CamsGear.jpg

 

[69gt4speed]

btw not real thrilled on some of those slot designs per my dsm friends, some can slip. At the least I'd loctite them w the blue after you get what you want.

Usually per most ppls 2v theory w s/c 10 to 20 deg more exhaust duration and more lobe seperation. On a dohc 4.6 most s/c cams are 114 seperation w 112 for n/a. The idea is the s/c will force in air and fuel easy enough, getting gasses out needs more time or deg as it doesn't have the s/c to help. I can tell you on a modded street dsm duration is about 272 duration adv. But many 4v heads flow more on exhaust % wise than than a 2v so duration on exhaust is equal or lil less. I'd look at the crower stage 1 for zetec comparing to a dsm turbo 272 2.0 street setup. Call them at least. Too much cam duration sucks imo, don't need it on a 4v to make power. Won't idle etc.

 

[CaysE]

...

That picture is great man; thanks! :rockon:

Nobody makes cams for the SVT Zetec... regular Zetec cams don't fit the head, and this is pretty much a guessing game as I'm fairly certain nobody has attempted regrinds for positive displacement on this motor.

To throw another wrench in the mix, the intake cam uses VCT, so I'd only be able to adjust the exhaust side.

I think I need to get some real numbers on the SVTf cams and VCT before I start talking with someone who would do the work.

 

[meaty mac]

Call them at least. Too much cam duration sucks imo, don't need it on a 4v to make power. Won't idle etc.

+1 4V engines are far more sensitive to changes in duration than to increases in lift