Degreeing a Cam... What does it do?

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crunchie12268

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#1

• Dec 19, 2004

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I have heard people talk about this, I just line up the dots on the timing chain. I know there are places on some timing chains where you can advance the timing and retard it.. is that what it means? If you degree your cam, then does advancing your distributor or retarding it make things different?

 

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veryslow5point0

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#2

• Dec 19, 2004

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i would also like to know.

 

HISSIN50

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#3

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degreeing the cam and spark timing are different. degreeing the cam is for the actual valve events. advanced is generally for better bottom end response (depends on the cam) - it also allows the cam to run more towards straight up as the timing chain stretches. this all has to do with the cam events in relation to the piston position.

one can get adjustable cam gears to achieve this.

 

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crunchie12268

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#4

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ok... yeah that makes sense, does it benefit you a lot more if you degree the cam? Is advancing the cam with the marks on the timing chain the same? Like 20* advance and so on

 

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87GT 306

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http://www.cranecams.com/?show=degreeingCamshaft

 

HISSIN50

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crunchie12268 said:

ok... yeah that makes sense, does it benefit you a lot more if you degree the cam? Is advancing the cam with the marks on the timing chain the same? Like 20* advance and so on

Click to expand...

a typical degree would be more like 4* advanced or retarded.

degreeing is a good idea, even if one does not wish to advance or retard the cam. this makes sure one gets the cam dialed in just as desired (sometimes straight up, is not straight up).

 

5spd GT

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#7

• Dec 19, 2004

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Degreeing the cam is a form of checking to see if your valve events are in check...to match what the cam is supposed to do...

As Hissin said: Advanced is for more bottom end/Retarted is for more power up top...

Here is the website I used to degree my cam in...it is actually pretty easy to do...the degreeing kits are around $80 bucks off of Summit...

Especially if your looking at getting a custom cam - If you do not degree the custom cam in...you don't get the custom effect (or chance of it)...


http://www.holley.com/HiOctn/TechServ/TechInfo/IECCTech8.html

 

Michael Yount

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#8

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Example - if you were to install an E cam dot to dot it should turn out that the intake valve is opening to .050" lift at exactly 0 degrees - top dead center. If you were to install a degree wheel and actually measure where it opened you might find that the dot to dot install was actually resulting in the intake valve opening as much as 4 to 6 degrees either before or after tdc. This is because of tolerance stacking in the manufacture of all the parts that impact this measurement - how the cam is ground, how the hole (cam pin) is placed in the cam, how the cam pin hole is placed in the cam gear, how the dot is placed on the the cam gear, how the slot is cut in the crank gear, how the slot is cut in the crank, how parallel the camshaft is to the crankshaft, etc. Very slight errors in each of these areas can allow a dot to dot install to be as much as 4 to 6 degrees off of where it's supposed to be. With an adjustable gearset, and a degree wheel and dial indicator, you can install the cam so that the intake valve is opening within 1 degree of when it's supposed to according to the cam card. That's what degreeing the cam is. And any aftermarket cam, or careful assembly of a stock cam, should be accomplished that way.

Cam timing determines when the valves open and close relative to crankshaft/piston position. Ignition timing determines when the spark plug fires relative to crank position/piston position. Two entirely different things.

 

Michael Yount

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#9

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By the way - advancing cam timing for more bottom end and retarding it for more top end are generalizations that shouldn't be generalizations. It's really tough to know what's gonna happen when you change cam timing unless you have a model to help you predict it, or you try it and see what happens. There are lots of cases where advancing or retarding helped or hurt the entire power/torque curve. So we should be on a mission to stop telling folks you advance cam timing for more bottom; retard for more topend - it's simply not true in every case, and it's not true often enough to even use it as a rule of thumb.

 

HISSIN50

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#10

• Dec 20, 2004

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Michael Yount said:

By the way - advancing cam timing for more bottom end and retarding it for more top end are generalizations that shouldn't be generalizations.

Click to expand...

Michael, i am not sure if this was directed at me and what i said in my first post - here is the quote of what i said:

" advanced is generally for better bottom end response (depends on the cam)"

i knew this was not always the case, which is why i prefaced my statement with terms like 'generally' and 'depends'. i however did not know that this was so often not true (i thought it was most of the time). thanks for the clarification.

 

Michael Yount

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#11

• Dec 20, 2004

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Not aimed at you - aimed at all of us; I don't think that qualifying it by "generally" is even valid any longer. I'd say "occasionally - but not so often to make it worth mentioning...".

 

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crunchie12268

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#12

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so it is possible to degree a cam with the heads on? I think I am going to do that when I get my Heads and Cam. So with timing gears, I can adjust things easier? I would like to get some but they are pricey. Any opinions on what I should do?

 

1990Coupe

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#13

• Dec 20, 2004

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Ok i didnt put the cam in my other car, i had a friend do it who is way good with that kinda stuff. but with my new car, i wanna do the cam myself. With all the stuff ive done, it doesnt look hard or challenging at all.. Im going to purchase the crane cams degree kit that has all the tools i would need... can i do the cam install with the engine in the car?? i mean i know i can put the cam in the car no problem, i mean can i fit the degree wheel and all the other stuff i need on the engine to degree the cam while its still in the bay??

 

Michael Yount

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#14

• Dec 20, 2004

• #14

Yes you can degree with the cam in the car - I've helped Stangers do that.

Crunchie - heads on or off it doesn't matter; you can degree the cam either way. Same with p to v clearance - you can check that with heads on/off (clay) or with heads on - drop valve method. Most folks don't use gear drives - you need an indexed timing gear/chain set. It has a crank gear that has multiple slots so you can select usually in 2 degree increments up to 8 degrees advanced or 8 degrees retarded relative to 'straight up'. Be sure to degree the cam BEFORE checking p to v; cam timing impacts p to v clearance. All things equal, advancing the cam timing reduces intake valve clearance and reduces exhaust valve clearance. Retarding changes things the other way - more int. clearance, less exh. clearance. Here's a link with more info on another way to measure p to v with the heads on.

http://www.diyporting.com/PVC.html

Highly recommended that you do both - you'll learn so much about how your engine works.

 

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crunchie12268

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#15

• Dec 20, 2004

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so the drop valve method is a way to measure the Piston to valve cleareness??? that is cool! So I should do that before picking my cam?

 

Michael Yount

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#16

• Dec 20, 2004

• #16

Yes - if you're ordering a custom cam and do a drop valve map every 5 degrees or so from 20 before to 20 after tdc, the cam grinder can use that to be sure you don't have p to v issues. With an off the shelf, it'll be difficult to do much more than guess based on what others have had work, and then use the process to measure.

 

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crunchie12268

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#17

• Dec 20, 2004

• #17

It all makes sense...... I am going to go start my car up and rev it to 7K to see if I get any valve float.


Ahh, maybe tomorrow.