Explain an often misunderstood camshaft specification. Lobe seperation.........112+4

[prorac1]

What does the +4 mean. And do you install it straight up, advanced 4 degrees, is there 4 degrees built in, does that mean its a 116? Im confused. Please explain. Thanks, Eric L

[Fbomb]

+4 means there's 4 degrees of advance ground into the intake lobe, so you have an LSA of 112 but the ICL (intake center line) is 108* And if you install it straight up then you will have 4 degrees of advance on the intake.

[prorac1]

Ok, so what changes will that make over a normal 112 cam?

[prorac1]

What if any advantages would there be to installing the cam anyother way than straight up?

[JoeliusZ28]

From my "camshaft basics" sticky in the intake/exhaust section

"...Advancing a cam means you are moving the valve events earlier in the cycle. If done when installing the cam you will be moving both the intake and exhaust events earlier in the cycle. This generally boosts low speed torque at the expense of peak HP. Retarding a cam does the opposite, it will improve peak power by delaying valve events, which will increase peak HP and move the peak HP rpm up, but at the expense of low-end power...."

[prorac1]

Thankyou Joel, I wasnt aware of that. I have a cam that I want to run in the new motor, but im still in the planing stages, lol. Its a 237/244 duration @ .050 with .582/.592 lift with 1.6 rockers. Open and closing points @ seat are
IVO- BTDC- 10.5
IVC- ABDC- 67.5
EVO- BBDC- 71.5
EVC- ATDC- 6.5

116 exh centerline
108 int centerline
112 + 4 Lobe seperation.

Its a custom grind from Futral motorsports that we have hangin around.

Whats everyones thoughts. Eric L

[prorac1]

And fwiw, heres the valve events @ .050

IVO 10.5
IVC 46.5
EVO 58.5
EVC 6.5

Eric L

[ThreeHonks]

what lobe is that on and who is the core made by. I will never use anything other that a Bullet billet core.

EDIT: pertaining to the advance. Install is straight up, "dot to dot" method. The advance is good for it. The cam was designed in a way where it needs the advance. most latemodel cams that I see all have about 4 degrees of advance ground into them.

4 degrees is not much at all anyway. You wouldnt even notice it, even if it was +0. By the time you take valve lash, rocker arm deflection, stud movement, and pushrod deflection, it will be a wash. Its all about what the VALVE sees, not what the cam is ground to be.

[JoeliusZ28]

JMO but if youre gonna go with that nasty of a cam, might as well man up and do a solid roller too. unless this is going on a 396 to tame it down.

[prorac1]

Its a hydraulic roller ground by futral motorsports. I still need to call them and find out if its a billet core (unless you know a way I can tell visually), and if the gear on it is compatible with my stock oil pump drive, etc. Thanks, Eric L

[prorac1]

And its a pretty good sized cam, but I wouldnt call it nasty. Its just a touch more agressive than I was looking at. Its a 383 so the extra cubes will help tame it down a little. We have it sitting around from another project so we figured we would throw that and the matching valve springs in. If we dont like the street manors ill drive it for a few months on the highway in 5th i figure and we will do a cam swap, lol. Sounds good in theory......................right, lol. Eric L

[ThreeHonks]

how old is this cam and what lobe is it on and who is the manufr?

.050" duration and lift numbers tell very little about how a cam is going to perform

[farmington]

Lobe separation is NOT adjustable. The separation is the actual degrees of difference in how the intake and exhaust lobes are ground. You can modify the installed centerline by advancing or retarding the positioning of the camshaft. Retarding the cam will bump up the top end and kill off a little bottom end and advancing will do the exact opposite.

[prorac1]

Thanks for the help guys. The cam was ground by Futral motorsports. What do you mean by what grind is it? Not sure on the exact age. I think around 4 or 5 years old. Compared to other custom grinds ive looked at, it looks to be comparable numbers valve event wise. Whats your thoughts gang? Eric L

[1BADAIR]

what lobes?