2.2 'S' cams

[Scott Clarke]

EBS has factory original S cams for sale right now at something like $325/each. One hell of a deal.
-Scott

[ttweed]

Originally posted by fryardds
For instance the spec sheet says for 05-261 is:
Valve lift is .476/.450
Duration in deg. is 284/270
Duration @ .050 in deg. is 264/248
How do those compare to the stock 'S' cam?

Brian-
I think the stock S cams have 267i/235e duration and .459i/.356e lift, so that is a bigger cam that you have. It is what Webcam calls their "120/104" grind. The 911S grind is 05-061, not -261.

TT

[Rick Cabell]

All factory MFI cams are the same.
If you need a cam, send it to Dema Elgin.......end of story.....
It will be right!
Much cheaper than buying two new cams from whoever.

[fryardds]

Marco.

We haven't adjusted the pump at all and previous owner probably didn't either. As you say there is a real possilbility that the cam timing is off. Thanks for your input

Tom and Scott thanks also for the info. Now I can see what the differences are between the two cams. That is a good price, but Rick is right it is much more economical to regrind the hard welded cams back to 'S' specs. Rick do you prefer Elgin over Webcams? Thanks.

[Bobboloo]

Looks like an off-season top end rebuild. You and the rep from Webcams are saying the same thing. I really don't understand cam terminology and what the exact differences are, but she mentioned the overlap difference as a reason to up the compression. For my own knowlegde could you explain the differences in the specs. of the stock vs. the 05-261 cam.

My understanding of what happens with a motor that has overlap is that the intake valve hasn't finished closing when the crank turns around and the piston starts it compression stroke and consequently a little compression is lost to the intake port. At high RPM's this affect is lessened due to velocity. This allows for moving the maximum amount of air at high RPM's (HP) but at a cost of low RPM performance.

Here's the spec's on the cams for comparison. The lift is in inches and the duration is given in degrees as always.

___lift ____duration

.459/.396__267/235__S cam

.462/.403__281/251__906 cam

.476/.450__284/270__05-261 cam

As you can see the 05-261 is an even more aggressive cam than the 906 cam which is a race cam from the 906 and the 911R race cars.

Either the builder of the motor made a mistake and ordered the wrong cam. (easy to do with their numbers) or the previous owner didn't understand the consequences of the quest for more HP with a limited displacement.


Send them back to Webcam. They'll make it right.

Make sure to check the port size on your heads because if they were building on all out race motor they should have enlarged the ports. The easiest would be to check the intake as exhaust studs have a tendency to break when you remove their nuts.

The intake ports should measure 36mm for an S spec motor.

[Rick Cabell]

Elgin!

[fryardds]

Bobby,

Thanks for the info and explaination. Makes more sense now. The builder must have ordered the wrong cam because the owner thought they were 'S' cams. The intake ports are 36mm. I remember that measurement from when we had the throttle bodies rebuilt.

Thanks again Rick. Elgin it is.

[Chuck Miller]

This is an interesting thread for me …

I realize my situation is different but it will still be interesting to follow up on.

I have indeed put in the WebCam 120/104 grind in my 2.4-S to 2.7-RS conversion…

I did A LOT of homework before I decided to change out my S cams…

The governing factor in the decision was the 300cc increase and the 9.5 Adail/Mahle piston set…

Everything I've read and heard tells me I'm going in the right direction…

If I just rebuilt the 2.4 I believe I would have stayed with the S cams.

In about a month (I hope) we'll see…

I have kept my S cams just in case… (did the WebCam 120/104 regrind on some E cams)

BTW … I'm REALLY expecting a difference to the good from these cams...

Until then…

Cheers,

[Rick Cabell]

The word has been that you are not to touch MFI cams or you will go backwards.
Dema Elgin has made positive changes with the MFI cam. Chuck has gone forth with Web cam. I am anxiously awaiting Chuck's results.

[Bobboloo]

The word has been that you are not to touch MFI cams or you will go backwards.

This makes sense considering how the MFI motors are so sensative to exhaust changes. One would think that the same might hold true on the cams in that if the exhaust lobes aren't matched correctly to the intake ,for MFI use, that this could also upset the balance and cause flat spots not unlike what Brian found. Then again his flat spot could have been completely distributor related but it's something to think about.