degreeing cam shafts (real hidden HP)

[wheatlandbrawler]

well as some of you might have noticed by my build i am a do it your selfer, all the way down to my engine and trans builds. when i built my first engine i did the age old line up your marks at top dead center bolt it togeather and go.... man was i wrong. after an afternoon of hanging out at A.E.M. the local race shop. and dyno spot a guy took in a circle burner engine that he built at home but wanted to see the numbers it was layin down. it was your standard circle burner claimer engine, nothing really fancy. so they fire it up for its first pull, and the thing was huffin just to make 386hp..... so imidiately everyone goes into trouble shooting mode... they go in pull the valve covers off, and distributor pull out the timing light and go to checking everything over. everything within reach seems to be fine. they button it up and make another pull this time with a little more timing in it..... it started detonating and made 372hp. so not only is this guy sweating a little bit but the shop owner is a little confused. so he asks what would prove to be the question of all questions. "did you degree your cam shaft in?" and the guy said no.

(remind you i have never degreed mine in either) so they got out the degree wheel a dial indicator and piston stop with a calculator and got it degreed in according to the cam card.

they made a pull after degreeing the cam in and it yeilded huge results i was simply amazed. it went from making 386hp to 447hp this was after feeding it some timing through out the pulls as well but i was amazed. i imediately went home and bought a degree wheel.

so i got my cam degreed in now. its so much easier then it looks. so i recomend doing it if you havnt!

[wheatlandbrawler]

oh i also left out a bit of vital information... they had to put a crank gear on it with pre cut advance and retard keyways. essentially degreeing your cam in is only to make sure that everything lines up where it is supposed to. and if not make adjustments accordingly.

[Marv D]

Today's quality timing sets are 'usually' dead on and degreeing is simply a check to make sure nothing screwed up in the factory. Like wheatlands story shows,, it DOES happen.

I will say using only Cloyes timing sets (for fixed gears) for the last couple of decades, I've never found one off enough I could find with a 16" degree wheel. But that doesn't mean Cloyes isn't capable of having the same issues as everyone else. Just I've had great luck with Cloyes.

That said,, be very cautious in which method you use to degree the cam. The 'crown' of the lobe (chasing down both sides down from max lift) will give you the degree of the point of max lift of the 'crown' of the lobe. On cams that the lobe is symmetrical that works fine. BUT many of today cams are asymmetrical in the upper end performance grinds (flat tappet OR roller) With more aggressive opening ramps and softer closing ramps, the 'crown' doesn't really tell you crap about the opening and closing timing. But IF that's what that cam grinder suggests, USE IT!!!

Many custom cam grinders will tell you to degree the cam using nothing but intake tappet OPENING 0.050". In other words, if the cam card says the #1 intake tappet lifts 0.050" at 20° BTDC,, you degree the cam to be 0.050" open at 20° before,,, and pay NO ATTENTION to anything else. Not lift, not crown of the lobe, closing.... nothing. Usually they have ran the cam through a CamDr report and KNOW what everything else is going to be IF you set it to intake opening.

Others will tell you to to use the 'lift at top dead center' method. This one is pretty screwy if you ask me, but some cam grinders like Cam Innovations demand you use it. It's a heck of a lot easier if your using a timing set like the Cloyes Hex-adjust,, but in general you bring the motor it TDC #1 and you 'should have' some prescribed intake tappet lift (like 0.1001 or whatever) They will generally tell you that TDC is some degree after the intake lobe center-line. Helps zero in on the very specific and accurate lift they call out.

AND LASTLY,, the 'mean' of the 0.050" opening and closing to determine DURATION center-line. Pretty self explanatory,, degree of 0.050" opening, + degree of 0.050" before closing,, add two together and divide by 2,, you have CENTERLINE of that lobe. Adjust as necessary to match cam card.

Wow, hows that for taking a simple subject and making it complicated!!! Which to use??? Good question. Ask a dozen engine builders and a dozen cam grinders and you can get any one of these as an answer. Above all else, follow the cam grinders instruction!!!!!! If they say use one method (such as Lunati says use the crown of the lobe method,, Comp says use the mean of the opening + closing /2) USE IT!! Never hurts to check every aspect of the cam so you 'know' the accuracy of the cam card and the grind. But always start with the manufacturers instructed degreeing method. There may well be good reason to.

IMO.. it's more about the intake valve CLOSING!!!! Cylinder pressure is all about mechanical compression ratio, and that intake valve closing. I use the intake valve opening 0.050" method as a starting point, and then check the intake valve CLOSING. If it checks the cam card,, fine. If not I'll let the opening event go a few degrees if necessary to get that intake valve closed EXACTLY on time.

but, that's just my 2¢

[wheatlandbrawler]

that should clarify the "how and why" as to if you need to do it or not. when i asked why it should be checked mark said " with todays cams being mass produced and some guys running common grinds blanks that are ground at the end of the day may have a looser tolerance in comparison to the one that was ground fresh in the morning" ? hell i didnt know much about it. but i found out it is incredibily easy despite how hard it sounds. and mine ended up checking out perfect. but it is a cautionary measure that is worth checking in my opinion.

thanks for your two cents marv, i was prayin no body would ask me how to do it cuz i didnt want to type that much hahaha. if all that info is only 2 cents id love to see what a dollar could get a guy. hahahahahaha

[82Cecil]

I'm running a budget grind, so I checked mine for the first time when I was changing heads last Dec. It was on the money. I took a lot of pains with it to be sure of the readings.

I agree, it is absolutely worth the effort to know.

[chris mc bride]

Being dragracer and mainly crewchief for alcohol funny car and dragster.I can tell you there is no such thing as a wasted move when checking specs for any engine part.I never install a cam without degreeing it in anything.Cpl of reasons for one I know where its at,I know if I want to change it later i will know where it will be at.Another reason for degreeing it is sometimes you want more top or bottomend power this can be done by moving the cam.Normally 4 degrees is good for 500 rpm shift in powerband.Advanc it for bottm end and retard it for topend power.