Contour Enthusiasts Group Archives Forums Modifications Duratec Performance Cams: SVT vs. Regular

Found this interesting (from the SHO Shop catalog update):
"Before moving onto exhaust lets look at the camshafts. They were designed by Roush for SVT. When measured on Cam Doctor they offer exactly the same lift and duration as generic 2.5L. What makes them unique is a lobe separation angle. The camshafts are manufactured by wedging a lobe onto steel tube. This design allows one to retard or advance lobeâ??s location. It appears that Roush simply increased overlap between intake and exhaust cams, moving power band further up in RPM range. We are also evaluating several lobe profiles that we have used successfully on SHO engines. When testing is complete we will release them for sale."

So it's just the lobe separation angle that's different. Interesting. I wondered when Warmonger made his measurements why he could not see a difference in the lobes (lift/duration), now I see why.

I'm also curious to see what kind of cam profiles they come up with (or will it be just vaporware?)

-Lance

I think this was discussed many times when it was established that the only difference re SVT cams was the overlap, by about 4-6 degrees up Vs stock.The 'Presta' 'coposite camshafts make it easy to do tis as the components are 'splined' to each other before a broach is drawn thru the hollow shaft expanding and locking the part to the shaft,same lobes etc as stoc just put in at more overlap cam positions before expanding/locking the parts....pity they dont come apart as easy!

Originally posted by Terry Haines:

---

...pity they dont come apart as easy!

---

They do come apart pretty easy... it's just getting it done in a reuseable fashion that's so hard! My girlfriend *helped* me remove part of one of my spare sets of regular 2.5 cams. When she told me, I flew out to the garage to inspect the damage... Thank God it wasn't one of the three SVT sets I have sitting out there waiting for install. I'm building a box to hold them all in my office tonight... not only to support them from warping, but more importantly to keep people from knocking them over!

This explanation doesn't make sense. We are not talking about a single camshaft that functions both intake and exhaust cams like the overhead valve cam in block engines.

Since the intake and exhaust lobes are on seperate shafts, increasing overlap would be done by degreeing one or the other of the two shafts. That is the overlap or split could be changed merly by how each individual camshaft is installed.

It is common on the OHV engines (Chevy 350 for example) to increase overlap by changing the angle between the intake and exhaust lobes. Known as the "split". The character of the cam can be greatly altered by changing the split while the lobes stay the same. Mild RV cams are often 114 degrees split while hotter cams are often mote like 108 or 110 degrees.

Variable valve timing in modern engines alters this split while running depending on commands from the PCM. It is common to alter only the intake cams on performance oriented engines or sometimes to alter only the exhaust cams on emissions oriented engines.

Without getting into a huge discussion on valve timing something about changing the overlap on the Duratec from the above explanation doesn't ring true. Am I missing something?

Changing the cam lobe position vs. the actual cam gear is what you're missing. Since the cam gear is the interface between cam position sensor and the ECU to fire the ignition modules (along with using the crank position sensor as well). By changing only the lobe position, the cam gear position stays the same, as well as being able to position the secondary lobe even further apart. Since our engines do not offer variable valve timing, the physical orientation aspect of older engines still holds true, even with two cams per head to play with.

I guess I'll remain confused. I still don't see it.

How about this..the rod portion of the cam and the cam gear on both cams will have to be in the same place due to the link length of the chain. Without adjustable cam gears, cam timing is fixed. So, to change the timing without adjustable gears, you have to alter where the lobe on the cam is in relation to the gear.
With the way Ford constructs these cams they slide the lobes on to the tube, then before the tube is "swelled" to hold the lobes they change the orientation a bit in order to alter the timing.
I belive this was done in the interests of cost as Ford could make a "new" cam by just adjusting pre-existing tooling and parts.
At least thats how I interpret this discussion.

Whats really interesting is that SHO cams are built the same way and many of them are failing[lobes coming loose from shaft and opening valves at the wrong time] and destroying engines. Geuss what, Ford is'nt warrantying them either! Imagine that. "Ford we have a better idea"

Couldn't just the relationship between the sprogket asnd shaft be changed. I see Jim's point. Why move 6 lobes when you can move one sprocket?

Originally posted by Contouraholic:

---

Couldn't just the relationship between the sprogket asnd shaft be changed. I see Jim's point. Why move 6 lobes when you can move one sprocket?

---

Sure!! Thats the easy way to do it. Did Ford take the easy and CHEAPER route or did they take the more expensive route?