xanadu wrote:Sorry to hijack the thread, respond or not. Was curious as to what differences engine builders have seen with carburettor operation for a given tuned engine / say a 383 600HP engine with a cam installed on a 106ICL, then dialling the cam in on a 108icl or a 104icl. Is there much required in carb tuning for this adjustment, as in with the 106icl, the afr's on idle / cruise and WOT are good, has anyone seen a major change with icl changes?
Hope it's not too confusing...
That depends upon THAT particular engine as no two combinations will react the same.
Example; advancing the cam 4 degrees in one recent combination on the dyno made more TOP rpm horsepower, probably because the exhaust was lacking and it needed to open that valve sooner.
Cam card shows lobe separation of 108 deg with the intake centerline of 102 deg. Cam installed using the 102 deg as the centerline but the cam is actually 6 deg advanced because the 6 deg is ground into the cam. Is this the correct way of looking at this?
gramps wrote:Cam card shows lobe separation of 108 deg with the intake centerline of 102 deg. Cam installed using the 102 deg as the centerline but the cam is actually 6 deg advanced because the 6 deg is ground into the cam. Is this the correct way of looking at this?
Advance or Retard is the difference between LSA and intake centerline.
If the LSA is 108, and you install it on a 102 ICL, then the cam is 6 degrees advanced. How much you had to move the cam from the "dot-2-dot" location to get to the 102 ICL is irrelevant.
mopar
The short answer to your last question is yes
CamKing gave you the explanation
besides what the card says what does your cam grinder say?
how much of a PITA is it to change in the car or are you pulling the motor on a regular basis?
with a stick and a light car you could retard it to what the cam grinder recommends with a phone conversation
the cam card may be a one size fits all card unless the cam was custom ground for your application
If it was a custom grind with all your inputs considered- go with the card
You do need a baseline before any real changes
The camshaft is ground on a 111 degrees centerline, if it is installed on a 105 ICL, it will be advanced 6 degrees, is that where you want it to be????
When I turned 47 years old, I entered into my 5th decade of drag racing.
Greywolf
It's an off the shelf cam, he's got it installed on the dots, which only diverge from the cam card by two degrees
Let's see how it works, it might be just fine, if not he will have a baseline to work from
let us know how it works out Mopar
we used to race a stock Chevy with the stock cam retarded 8 degrees- wound the snot out of it
whatever works
Will do, it should be in the car in the next month or so (waiting on it to come back from Maryland where it's getting a cage and being used to develop a new rear swaybar).
I've never seen those type sets be anywhere near their advertised position, even on the Cloyes stuff. I usually use the Cloyes Quik-A-Just, but every now and then use a customer supplied multi keyway type. The last one I used had four positions that made no change at all, and to get it to 108 I ended up using the -6 keyway. The cam was a custom Comp ground straight up on 110.
gramps wrote:Cam card shows lobe separation of 108 deg with the intake centerline of 102 deg. Cam installed using the 102 deg as the centerline but the cam is actually 6 deg advanced because the 6 deg is ground into the cam. Is this the correct way of looking at this?
wyrmrider wrote:Greywolf
It's an off the shelf cam, he's got it installed on the dots, which only diverge from the cam card by two degrees
Let's see how it works, it might be just fine, if not he will have a baseline to work from
let us know how it works out Mopar
What am I missing here,
the cam card says it is ground on a 111 centerline;
it recommends to be installed on a 108 intake C/L, which would be 3 degrees advanced....????
If it is installed on a 105 intake C/L then it's 6 degrees advanced....???
If I'm incorrect, could someone please explain..
When I turned 47 years old, I entered into my 5th decade of drag racing.
Force Fed Mopar wrote:If you have a cam that recommends a 108 installed centerline, and it has a 105 centerline when installed straight up, do you go + or - on the adjustable timing gear set?
In this case, a 108 installed C/L would be 3 degrees advanced, (ground on a 111)
and,
if it has a 105 C/L when installed, then you are 6 degrees advanced.
would it not be????
When I turned 47 years old, I entered into my 5th decade of drag racing.
As I see it the cam was "Ground" with 111 degrees of lobe separation (this you cannot change), and it was also ground so that when you install it 0-0, the intake centerline should be 108 degrees. Again this is GROUND into the cam. So if all things are as the cam grinder intended the cam is 3 degrees advanced to crankshaft.
Now if you find that. after finding TDC precisely (with dead stop either side of TDC and then taking half the number of degrees and adjusting your degree wheel accordingly), your indicated intake centerline is 105 (again by taking a reading on either side of max lift of the intake lobe, adding those numbers together and dividing by two to get an accurate lobe centerline), then the cam is installed 6 degrees advanced to the crank.
If you do not do the establishment of TDC and Intake lobe centerline accurately, it all means nothing.
In any case it is not unusual for cam grinders to put in 3 degrees of cam advance (particularly for "shelf" cams that they expect simply to be installed 0-0). You will eventually lose this as the chain stretches. If it has an additional 3 degrees, and you can accurately ascertain this, then it simply means the motor will have a bit better low/mid range performance and perhaps lose a small incremental amount at the top end.
Almost all the cams that I sell have 4 degrees of advance built in when installed 0-0, as 90% go to people who would not know how to use a degree wheel. For the ones that do, I provide assistance to help them determine what the actual installed specifications are. You will really only know if advancing or retarding the cam makes any noticeable difference by doing a lot of testing at the track or on a dyno. Even then, gains shown on the dyno may not translate directly to the track.
As I said in an earlier message, install it and run it.
