Degreeing reground cam...

I've installed a .520 lift cam in my engine that I'm putting together. It is a regrind by Compcams. After degreeing it using the "centerline" method and the .050 valve lift (open and close) degree method...it only looks to be 1 degree off (retarded) with my new timing set and engine setup. Is this possible? I had the idea that it would be around 5-7 degrees advanced.

If the cam specs would be useful, they are found in Burbank95sc's post from around a year ago (for sale ad) I'll attach the picture later today.

Here's the Specs

You can't use the centerline method because the lobes are not symmetrical. The open side of the lobe is different than the closing side.

You have to use the duration method.

And in the end youll probably leave it in as is anyways :O)

The "duration method" is what Crane Cams recommends, correct? As found here:
http://www.cranecams.com/?show=article&id=3

I tried both ways and got results very close to each other (within 1.5 degrees)

Here are the valve opening and closing (measured at .050 tappet lift) that I got for the intake and exhaust valves

Intake: open: 4 ATDC close: 38 ABDC
Exhaust: open: 42.5 BBDC close: 1 BTDC

With these values, is it possible to look at and compare to the cam card and see what needs to be done? I have a feeling that I'm making this more complicated than it actually is.

DamonSlowpokeBaumann said:

And in the end youll probably leave it in as is anyways :O)

Click to expand...

Now what is that supposed to mean?

With these values, is it possible to look at and compare to the cam card and see what needs to be done? I have a feeling that I'm making this more complicated than it actually is.

Click to expand...

Thats what I mean.

Seriously though never a bad idea to degree a cam. I personally dont wanna be bothered and if by chance my cam isnt exactly where it should be....Then there is the timing chain issue! (And whos to say where you find th4 timing to be is 100% correct or wether it will hurt or improve performmance)

Then after degreeing the cam..modifying the timing chain to be able to actually modify cam as installed....Ya have to wonder....MAYBE I should have bought a new grind...Then of course that could be off....

Now back in the day when engineering tolerences in manufacturing componants were not on the ball this was a larger issue.

Now I wonder what people have noticed when degreeing thier stock SC cams...because that is just what will help you the most in my opinion. Dont think they can regrind thr cam timing

DamonSlowpokeBaumann said:

Then after degreeing the cam..modifying the timing chain to be able to actually modify cam as installed....Ya have to wonder....MAYBE I should have bought a new grind...Then of course that could be off....

Now I wonder what people have noticed when degreeing thier stock SC cams...because that is just what will help you the most in my opinion. Dont think they can regrind thr cam timing

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Do you mean modify the cam or crank sprockets to properly degree the cam? I don't think there's much you can do the the actual timing chain.

There is a bit more that goes into using a reground camshaft versus a new grind, but when you're talking a $200 difference, it may be worthwhile.

Modify the crank gear by cutting a new keyway in place. Me..I'd just put it in

The main benefit we have to degreeing the cam when we put it in is that when XR7Dave is scratching his head why it isn't working the way he expected when tuning it, we can mention, oh yeah, the cam was off when I put it in. Then he can slap you for telling him that now, and he goes back to adjusting all the tables in the SCT software.

Really, unless it is way off, there isn't a need to worry.

I put a new cam in my motor. Was supposed to come out 4 degrees advanced... I checked it 4 times, ended up just 1 degree advanced. Not perfect, but good enough.

how did you verify top dead center? That has to be spot on exact. How are you measuring lift? If anything moves, or you didn't set tdc correctly, you'll never get a good reading.

My dad and I made a positive stop for the piston (the heads are already on) out of an old spark plug and a bolt. We busted the porcelain out of the plug, welded a nut on the outer end, and threaded a headless bolt in from the other end. Using a locknut on the outside to keep the bolt even more steady when screwed into the head. I then guessitmated where TDC was, turned the crank a little to back the piston down into the bore, inserted the positive stop, turned the crank until the piston touched the stop, took a degree wheel reading turned the crank the opposite way until the piston touched it again, took the other degree wheel reading and re-set the degree wheel pointer to exactly halfway between the two readings. I did the process four or five times to make sure I was accurate...and because it was fun.

I'm fairly certain that I'm degreeing the cam correctly, I guess I'm just questioning what I should be getting for readings! I can take the readings and everything, but I'm just not 100% sure that I know what they SHOULD be.

Well Mike, it's reassuring to know that it doesn't have to be right on the money....just when is "too far off". I mainly concerned that it WORKS when I put it all together. It'd be nice to be at the optimum position, but my thoughts are that if the measurements I make are 1 degree off, then the new keyway is 1 or 2 degrees off, there went all the sweat to get it perfect anyway. I remember the guy that I bought it from saying that they didn't degree it correctly or something when he installed it, and I don't want to put this motor together (that's been a 4 YEAR LONG PROCESS!) and it not run correctly.

So, after looking at my cam card and my readings, what do you guys that have done this before think about just leaving the cam where it is? Should I make any other measurements concerning it at this time?

The cam will function fine within a reasonable range of it's design. Your power band will be affected but it will be within 5 hp within the 1500-5500rpm range. You will not likely be able to make a keyway that will be precise to within 1 degree anyway.

If the cam calls for a 4 deg advance, I would consider 7 deg a max advance and 0 deg a max retard before doing something about it. Retard will increase your top end at the expense of low end and advance will do the opposite. There are many other factors that will have a MUCH bigger impact on the end result than a couple degrees of cam timing.

damn im just lame I set cam timing by which one makes the most cranking compression using off set keyways from a different engine i have layn around

XR7 Dave said:

If the cam calls for a 4 deg advance, I would consider 7 deg a max advance and 0 deg a max retard before doing something about it.

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When the "cam calls for an 4 degree advance" - is that the amount you found you need to get the cam timed as recommended on the cam card? So whatever the cam manufacturer recommends, you say if you end up with 4 degrees retard or 3 degrees advance of that recommendation, then you're okay? (In which case I'd be 1 degree retard of the cam specs)

Thanks for the help guys

mannysc said:

damn im just lame I set cam timing by which one makes the most cranking compression using off set keyways from a different engine i have layn around

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We've got an all-star cast on this thread! I feel honored!

Manny, why not just make your own offset keys with that scrap hunk of metal you found out by the highway? - I would have expected a more ingenious solution from you. So you just stick with whatever provides the most cranking compression, which would be advanced as possible, right?

DrFishbone said:

When the "cam calls for an 4 degree advance" - is that the amount you found you need to get the cam timed as recommended on the cam card? So whatever the cam manufacturer recommends, you say if you end up with 4 degrees retard or 3 degrees advance of that recommendation, then you're okay? (In which case I'd be 1 degree retard of the cam specs)

Thanks for the help guys

Click to expand...

I wouldn't take it quite so literally. A 1-degree difference is hard to tell when you are aligning these sprockets and such. The cam card doesn't really tell you where you must align the cam. It is just telling you that the listed opening and closing points are based on the cam being installed a certain way. In this case, it says the points are based on the cam being installed at 109 degrees, right on the intake centerline. Now, you can advance or retard the cam by any amount you see fit, but that is your decision. I think you can do so by a few means, namely 1) aligning the sprocket with a different chain link (only for large adjustments), 2) Using an offset keyway, and 3) using an adjustable sprocket (I don't know if there is one for this engine). Dave's post pointed out what the general effects of advancing or retarding a cam are. To find maximum power would be an iterative process based on picking a point, tuning and dyno-testing, adjusting the cam, re-tuning, re-testing, and so on. Nobody wants to pull the front cover off umpteen times unless they are racing for some serious money, so "close" will do just fine for 99.99% of us. Then you can just tune it as it stands, making sure that your tuner knows approximately what the advance or retard is.

Anybody feel free to correct me if I'm wrong in the details here.

hell yeah as advanced as possible i like bottom end and yes I have made keyways out of scrap. Im cheap

its a olde david vizard trick he is my idol

Like I said...Just put it in!

DamonSlowpokeBaumann said:

And in the end youll probably leave it in as is anyways :O)

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I bet you're wondering how long this will go on until I say "I'll just leave it like it is!", huh Damon? Like you said, I probably will and like S Mazza said, I don't want to take the front cover off (ever) again on this motor, so I want to make sure I know what's going on before continuing. I think I'm almost there

just close yer eyes and ignore it . install it forget about it lol

I have not degreed a cam in yrs ever since i read david vizards books on engine hp ive just did what i said and ive been very happy with it but im no racer just like a very resposive street engine ill settle for my low 13 sec sc any faster ill break sumthin any slower ill shoot the car

DrFishbone said:

When the "cam calls for an 4 degree advance" - is that the amount you found you need to get the cam timed as recommended on the cam card? So whatever the cam manufacturer recommends, you say if you end up with 4 degrees retard or 3 degrees advance of that recommendation, then you're okay? (In which case I'd be 1 degree retard of the cam specs)

Thanks for the help guys

Click to expand...

The situation where a cam would be installed outside of the range of 0-7deg advance is very rare. Most cams are ground 4 deg advance because that works best in most situations. The cam listed above is ground roughly 3 deg advanced (and according to your results, actually 2 deg).