More information to peruse:

Stock Cam - 264 degrees
Intake: 22 BTDC / 62 ABDC
Exhaust: 61 BBDC / 19 ATDC

#101 Grind - 272 degrees
Intake: 10 BTDC / 39 ABDC
Exhaust: 41 BBDC / 8 ATDC

#293 Grind - 248 degrees
Intake: 10 BTDC / 38 ABDC
Exhaust: 40 BBDC / 8 ATDC

I'm getting some drawing paper out and seeing if I can chart overlap and other charecteristics.

BTW, the tech rep told me the #101 would probably work better with 11.0 compression. The #293 needs a bit more compression to make the power we're looking for.

 

Jellyfish brought up a very good point to always consider when messing with cams. Camshaft Centerline Timing.
Also when measured it's inportant to take valve lash and the amount of lift into cosideration when measuring the events in an assembled engine. Also degreeing the cams to a specific centerline would be very helpful to achieve a specific powerband.

Centerline is calculated from the following example:
Per the supplied data above, the stock intake cam is as follows.

Intake Opens 22 BTDC + Intake Closes 62 ABDC + 180 = 264(this is the duration) 264/2 = 132 132-22 = 110
Centeline is 110 Deg

Some of the numbers is the above data from Web Cam don't match up for the events and duration.

I know there will be lots of questions around centerliner vs. lobe seperation. Rather than write a book, I attached a link to a very nicely written tutorial on cam timing.

Hope this helps your decision, and most of all let of know how "seat of the pants" result.

http://www.compcams.com/Technical/TimingTutorial/

 

Oh no not another post with math.....

 

.


I thought it was me, both cams are almost identical in the timing events. How can the duration be so different???

It was driving me nuts, I am glad somebody saw it too. Does anybody have an explanation???

 

From what I see by graphing both these cams is that #293 is a fairly high intensity "small" cam, giving about the same 050 duration as the #101 but considerably less total duration @ 0 lift. I would think the #293 would be better for building more low end in a lower compression motor. It would bleed off less cylinder pressure but have a good amount of flow.

It would be interesting to see both of these cams plotted, I would guess they would be very close with about the same area under the curve. The #293 with less total duration, little higher lift and more aggressive ramp. vs. The #101 with more total duration, less intensity, a tad less lift, but about the same duration @ .050. Some flow actually happens below .050 lift but not much. The extended total duration can lower low speed cylinder pressure a bit.

I agree totally with the centerline commentary, I know that is where most of the interesting stuff happens.

When I did some graphing, I do belive that the timing specs provided were stated at the .050 lash setting. I attempted to build the data, but I was not successful.

I do think the #101 grind might bleed a bit of compression off, but with a 11.5 to 1 or 12.0 to 1 compression ratio, would still make adequate low end power and the mid range would be better than the #293.

Of course, this is simply my opinion.



DJFields, you have the ability to plot this information, it would be greatly appreciated. If you have a fax machine, I'll have them fax you all hte cam data.

 

You are a brave one for tackling this cam thread Marty! Please guys keep the post's coming. don't be shy !!

 

Jellyfish,

One thing I have NEVER been accused of is being shy!

Just one of those things where we need to find out more information. I always thought that's what these forums were for, pooling our resources, knowledge, intuition, su****ions and "how to clean" recipes!

Seriously though, I just wanted to start a meaningful discussion. It has been awhile since I've made any cam selections and this is the first time I've ever worked on a single cyliner with more than say 3.5 horsepower!

 

Thats pretty cool, I have been reading about cams since you started the thread. Most of it applies to cars though. It is just as you say pooling of knowledge and resources. Not the least Marty I was trying to encourage other members to jump in too with thier .02 cents.

It's funny how all the articles talk abouth cams as Voodoo or
Black magic hahah

If earth was a crank would midnight be TDC??? when the moon and sun are visible at the same time is that Overlap??? haha I am Nuts!! Why be normal!!

 

I just found out something. Web cams likes to get your cams and then build the grind on them.

Guess what? KACR is still there!

Just thought y'all would like to know.

 

Thanks guys,
Has anyone installed performance cams yet? If so is the KACR still an issue. If it is no longer there, are there any starting problems? I am thinking 330cc big bore and cams at the same time!