Russ Collins RC 388 camshaft Identification

Nessism wrote: Those Webcam specs are measured at .050" valve lift. Most likely the Russ Collins cams are not.

On the spec page Web gives both "advertised" and 0.050 duration. For the 118 grind it's
Advertised Duration: 286°
Duration @ 0.050": 245°

So yes, the numbers are very different at 0.050. But I used the advertised number because I'm guessing it's more similar to how the others are measured? The yoshimura sheet says they are measured at 1mm, so 0.039.

Edit: I see, the open/close angles for the 118 (17.5/47.5) appear to be at 0.050, and that is what I used for the overlap. I don't really know. The RC spec sheet says 0.050 for cam adjustment....

Don't know if this could help, but I still have the booklet that came with the Web cams that were used in my current motor, (from back in 1989). The written in #'s were for that build.

I have no idea what these following numbers mean but I found the following formula. @.050 the opening value plus the closing value plus 180 equals total duration. Thus 43 +83+180=306. the duration seams correct. Why so much duration with a small lift? Again just reading on the internet more duration is good at higher RPM as it allows more time to fill the chamber, but higher duration at lower RPM, the valve is open to long reducing Compression pressure. Wouldn't smaller lift (less flow rate) correct the longer duration at lower RPM? But Why what is the reason? I'm talking why beyond my knowledge. just adding information to fuel thought.

Lower lift is easier on valve train parts like the valves, seats, springs, etc.

Mikaw, alternative cam selection is a mystery to me too. Seems people in the know of the subject always have a preference, ditto's religion and politics. I only restore back to original, makes it easier for sure. I know it's something i need to learn about though!

Another important variable is the amount of overlap; that is, how many crank degrees are both valves open at the same time. As I understand it, greater overlap is useful for scavenging at really high rpm, but comes at the expense of a rough idle and lower cylinder pressure, especially at lower rpm.
It is all very complex, and partly voodoo.

Nessism wrote: Lower lift is easier on valve train parts like the valves, seats, springs, etc.

Thank you. So would the smaller lift fix the longer duration problem at lower RPM and help keep the compression up? In theory if what your saying that its easier on the components then if my hypothesizes is right also, this would be a cam that will increase performance at lower RPM while also being better for the valve components. If all that is true it sounds like a Win, Win.

Again I'm only throwing out ideas, Shows how much we miss the experience of Larry

Asphalt900 have you had a chance to check the lift on yours? Did the head it was in have any clearance cuts?

Missing LC for sure, but I bet Zed1015 and APEJay could school us on the matter.

Mikaw wrote:

Nessism wrote: Lower lift is easier on valve train parts like the valves, seats, springs, etc.

Thank you. So would the smaller lift fix the longer duration problem at lower RPM and help keep the compression up? In theory if what your saying that its easier on the components then if my hypothesizes is right also, this would be a cam that will increase performance at lower RPM while also being better for the valve components. If all that is true it sounds like a Win, Win.

No, it's the duration which bleeds off compression and makes using high compression pistons viable. The high duration will cause a rough idle.

Mikaw i didn't even take a measurement before i sent them back to the owner of the engine, SORRY. He just brings me engines he purchases and i re-do them to original form. But Yes the typical bucket relief and x's ground off the camcover. The bucket bores for the head must of had some residual blast media in them because bores are in piss-poor shape. He dropped off this engine and picked-up the one i finished. Drove 13HRS and back 13HRS and still had enough energy to set it in the frame when he got home. And he is 70YRS old. I'll never complain again about being only 56, Ha.

Asphalt900 would you mind if we used this thread to learn about cam profiles and how the effect engines? Id like to learn more.


Also Could you reach out to him and find out if he would sell the cams?

No Problem, i'm all for fostering higher education. I'm sure the gent with the cams will sell them, probably see them on ebay soon. I posted the box of parts back to him on the 2nd so i would assume he has received them. I'll get an item # when i chat with him.