[Blown06]

I'm not a cam guy, but looking for a small education here. When people talk about advancing or retarding the cam, they are referring to the location of the intake lobe center line in ref to crank degrees...right?

If installing it according the cam card, then it is said "it was installed straight up" What are the effects of moving the cam back or forward? If my cam was currently installed 5* advanced compared to the ICL on the card.........what would I be looking to happen if I backed it up to "straight up"? What scenarios encourage one to move the cam and what are the desired effects and what are the real world effects?

Also, when a cam has advance ground into it, what does that actually mean? For example, a cam was ground on a 116* + 5*adv ICL. Why wouldn't it just be a advertised as a 111* ICL? (did I go in the right direction there?)

My numbers above are hypothetical. I'm just looking for some education. Please correct me if any of my terminology or numbers are incorrect.

 

[Ace0406]

Advancing and retarding of cam just changes the power in rpm ranges. If you adv cam it will make its peaks at lower rpm and if retarding peaks at higher rpm. By no way will it give you more power!

 

[pcnsd]

I have found that anytime there is a possible adjustment, that there is a sweet spot for that adjustment. I read in A Graham Bells 4T book much of what is stated above, but that has not been my personal experience. In my case advancing the cam raised both peak HP and peak torque in the target range and continuing to advance the cam timing continued to raise both outputs until... it didn't. Then I backed it up one spot. Advancing the cam timing will raise your DCR and change the compression degrees vs power degree duration bias of the camshaft. In Don Terrills book 'The HP Chain", he provides a formula to suggest placement of the ICL based on a number of inputs including DCR, IVO degrees, fuel type and manufacturers LSA. I have found it to be pretty close.

In answer to your question about ground in advance. It goes to the difference in meaning between LSA and ICL.

LSA (116)* is the distance in degrees from lobe centerline to cam TDC (0) with zero advance
ICL (111*) is the distance in degrees from lobe centerline to cam TDC (0) with the advance dialed in. At zero advance this would be 116*. Changing the cam advance does not change the LSA.

Regards,
Paul

 

[MaxFlow]

ICL + ECL )/2 = LSA

 

[joel f]

Advancing and retarding of cam just changes the power in rpm ranges. If you adv cam it will make its peaks at lower rpm and if retarding peaks at higher rpm.

 

[Hollister pullers]

I just literally did this change this week and pulled Friday. I retarded the cam 5 degrees and gained RPM, minimum 600. The motor always felt like it leveled off. Be sure to check VTPC if you have a large cam.

 

[tempname]

Advancing and retarding of cam just changes the power in rpm ranges. If you adv cam it will make its peaks at lower rpm and if retarding peaks at higher rpm. By no way will it give you more power!

I had a cam that picked up a bunch down low and up high when I retarded it 4 degrees. I was blown away. This thread could go very technical, and probably should. But each individual valve event has its role. I'm not smart enough to understand them, but when you advance or retard, you move all of the events.

 

[jmarkaudio]

There is power in advancing or retarding the cam to find what the individual engine wants. One of the cams I had in my SB2 engine made more power at 8˚ advance... Of all the cam events I think the intake valve closing point has the most influence.

 

[Ace0406]

Never have seen changing cam degree increase power a lot talking more than 5 hp. Maybe when you do change and see an increase that would tell me maybe the cam isn't the correct one? or cIose. Changing valve lash (seeing gains)tells me that also.think the reason I am stuck on it is because when guys over rev engines the cam dowel bends and retards itself. power band moves up a couple in rpm range. My experience. take how you want it.

 

[Mike Beck]

If you have enough valve to piston clearance, experiment and see what it likes. I didn't have that option, had to install the cam where I had enough exhaust valve to piston clearance, didn't feel like taking it all apart and cutting the pistons further.

 

[Graphic Man]

a dyno and a belt drive makes it a lot easier to fine and put the power where you want it

 

[Chris Uratchko]

Never have seen changing cam degree increase power a lot talking more than 5 hp. .

So if I had a cam with a theoretical centerline of 102 degrees, and put it at 115 degrees.... it would only change the hp by 5?

This whole discussion to me, is only more evidence that we are talking in camshaft grinding jargon, and not engine jargon.

Does an engine know what advancing or retarding is? Certainly not.

Advancing or Retarding the cam changes 'everything' in the open and close events....

Do I want an earlier or later.... IVC IVO EVC EVO.... if I advance the cam I have changed 4 events in the engine and manipulated the overlap.

I can't think of a more unclear picture and an unknown learning experience other than... my engine made more power by doing this.

 

[Widow_Maker]

So if I had a cam with a theoretical centerline of 102 degrees, and put it at 115 degrees.... it would only change the hp by 5?

This whole discussion to me, is only more evidence that we are talking in camshaft grinding jargon, and not engine jargon.

Does an engine know what advancing or retarding is? Certainly not.

Advancing or Retarding the cam changes 'everything' in the open and close events....

Do I want an earlier or later.... IVC IVO EVC EVO.... if I advance the cam I have changed 4 events in the engine and manipulated the overlap.

I can't think of a more unclear picture and an unknown learning experience other than... my engine made more power by doing this.

I find more and more that the majority of enthusiasts do not understand valve events.

 

[markadams]

If you have enough valve to piston clearance, experiment and see what it likes. I didn't have that option, had to install the cam where I had enough exhaust valve to piston clearance, didn't feel like taking it all apart and cutting the pistons further.

Same here Mike.

 

[Chris Uratchko]

I find more and more that the majority of enthusiasts do not understand valve events.

Certainly it's worth advancing or retarding the cam on the dyno for best power.... but this is not the way we learn.

Engine builders need to focus on individual events... this is where the learning process takes off.

 

[tomato]

Can advancing/ retarding bring the intake port to more beneficial air speeds sooner or later making the motor more efficient?

 

[dragracer300]

In my case the cam was a little to big for where i wanted to run it so advancing it 4 degrees brought the power band more into the rpm range i wanted.

 

[Uncle Paul]

I find more and more that the majority of enthusiasts do not understand valve events.

I find the majority don't know how to degree a cam in and as you started do not know what the numbers mean.

 

[buschracing]

Certainly it's worth advancing or retarding the cam on the dyno for best power.... but this is not the way we learn.

Engine builders need to focus on individual events... this is where the learning process takes off.

exactly...you just changed all the events, so which change did the engine benefit from the most? how do you know?

to get the real answer gets very expensive...lol