Cam degreeing. I totally don't understand.

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i would think there is a whole degree whweel kit out there with the piston stop set up wheel,and dial indicator.
 
I would think its a crucial step in optimal tuning getting that mechanical valve timing dead on.
 
Dartswinger70 said:
An issue I am thinking of is these newer outsourced parts, what if the "dots " are marked wrong. i have always ran mine dot to dot, but have degreed cams in tech school I have done it before but it was many years ago, and I probably didn't truly understand what i was doing. The teacher was like "good work" I said " i still dont know what i did...:)
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I've seen dots wrong, and dots missing, or even more confusing: the combination of triangles, squares and circles instead of dots.

Degreeing is just ensuring that valve events happen when they're supposed to. With symmetric cam lobes, the 'centerline' of a lobe is easy to find by measuring a known lifter displacement on either side of the lobe, and then splitting the difference to give a value that corresponds to the center of the lobe at a given crankshaft orientation.

Look at it this way, if the intake valve is supposed to close at 70 degrees ABDC (usually the most important number), and is an advertised 295 (@.002 lifter dispalcement) lobe - the intake valve must open 295 degrees before, which is 45 BTDC. So, 45 degrees, plus 180 from TDC to BDC, plus 70 = 295. Follow?
Now, to get intake centerline (mid point between the ends of the 295 degree) you can go from 45 plus 147.5 (295/2 = 147.5) which gets you 147.5-45 = 102.5 ATDC. Or alternatively, 180+70-147.5=102.5. The 180 is the degrees between TDC and BDC.

Basically, you're relating where the center of the intake lobe is back to the angle of the crankshaft at that point in rotation. Make sense?

In order to KNOW that your valve events are accurate, you must degree the cam. Dots can move, chains can have slack, lifter bores can be off of centerline, etc.
 
66fs said:
True, but how close is close enough?
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Depends on PTV clearance. Stock lifts and durations? Probably never be an issue even at +-8-10 degrees. Might feel different at either extreme, but it'll run.

More lift and duration and higher compression? Lots easier for +-10 degrees to cause concerns, and it'll be more apparent in power curve in the end too. Bigger potential, bigger effect.
 
I think people fuss too much about 'exact' cam position. Dot to dot, 4* adv or 4* retarded etc...
Unless you are building an exact duplicate that was dyno tested & the cam position varied to get best HP, it is just a guessing game.
David Vizard makes a very good point about cam position: the closer the cam specs are to being perfect for that parts combination, the more HP will be lost if the cam position is not optimised. The opposite applies.....
For the average Joe [ or John or Jill.. ], I would install it dot to dot. After the engine has been run, you can change the cam position to see what, if any, difference it makes.
 
moparmat2000 said:
If your using something like a roll master billet gear and chain setup you would think something like that would be dead on dot to dot.
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The quality of the chain set really doesn't correlate with how accurate the installation will be. That's because whoever makes the timing set may cut their sets a tick off from the camshaft and crankshaft. The camshaft keyway might be a little off from the crank keyway. Both could be off from the cam and crank sprocket. There's a lot of room for error when you're talking about 360 DEGREES of rotation. That right there is exactly why you should degree every single camshaft. Every one.

Now, if you use the same BRAND camshaft and timing set, you do reduce your chances of being of somewhat. Even then, since we're talking about degrees, there's a chance for discrepancy.
 
Bewy said:
I think people fuss too much about 'exact' cam position. Dot to dot, 4* adv or 4* retarded etc...
Unless you are building an exact duplicate that was dyno tested & the cam position varied to get best HP, it is just a guessing game.
David Vizard makes a very good point about cam position: the closer the cam specs are to being perfect for that parts combination, the more HP will be lost if the cam position is not optimised. The opposite applies.....
For the average Joe [ or John or Jill.. ], I would install it dot to dot. After the engine has been run, you can change the cam position to see what, if any, difference it makes.
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I don't and I can give you great example of why. I built a 454 Chevy for a guy years ago. I used a Comp billet set on a Comp solid flat tappet. I put the wheel on it. Came up 12 degrees retarded. TWELVE. The number after eleven and before thirteen. TWELVE. That's been about 25 years ago and I still have a hard time believing it. But it was right. I duplicated it five or six times. It took an offset bushing in the cam sprocket along with the nine keyway crank gear to get it right, but I did and it ran like the dung who flung. That right there taught me to check them all and if somebody doesn't want to pay me to do it, I'll load their junk on their truck.
 
Like said these days it applies because of all the foreign out sourced parts they dont care when they make it if IT works right its going to THE USA...:)
 
RustyRatRod said:
I don't and I can give you great example of why. I built a 454 Chevy for a guy years ago. I used a Comp billet set on a Comp solid flat tappet. I put the wheel on it. Came up 12 degrees retarded. TWELVE. The number after eleven and before thirteen. TWELVE. That's been about 25 years ago and I still have a hard time believing it. But it was right. I duplicated it five or six times. It took an offset bushing in the cam sprocket along with the nine keyway crank gear to get it right, but I did and it ran like the dung who flung. That right there taught me to check them all and if somebody doesn't want to pay me to do it, I'll load their junk on their truck.
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indeed. There is a thread in the BB section where things were lined up, cam was 8* retarded. It's in correctly now and the report is the car runs a BUNCH better. There are times this pops up when installing.

Just spend the time to degree the cam so you know it's installed where it should be.
 
crackedback said:
indeed. There is a thread in the BB section where things were lined up, cam was 8* retarded. It's in correctly now and the report is the car runs a BUNCH better. There are times this pops up when installing.

Just spend the time to degree the cam so you know it's installed where it should be.
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I learned a lot when I degreed my cam. Yesterday I got to the ignition timing. With the cam degreed correctly and the timing re-set to specs, it is a new animal. I can't wait to get it on a track or dyno. I had a timing set that allowed the adjustment of 8 degrees, so it was easy.

Degreeing a Cam, or not.....
 
Dartswinger70 said:
so what type of performance issues would arise going dot to dot vs degreeing? has anyone experienced a "revelation" when degreeing as in the car **** and git way better than dot to dot?
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Let's say the probable range of dot to dot installation might be from 4* retarded to say 6* advanced. That is a range of 10 degrees and a possible range of pressure change, in a small-block, of say up to 15psi, which is HUGE. And, if your design was already borderline at straight up, then, like said, you could be into detonation. But if you were already at borderline too low, now you have a slug.
But it doesn't end there.
Retarding or advancing a cam, changes the power peak, some say 100 rpm over 4 degrees. If the powerpeak comes down, then the power will be less. If the peak goes up, the power could go up. This is because Horsepower is a mathematically derived equation of torque times rpm. More torque at a higher rpm always results in more power at that higher rpm.

So after all this talk, what are we actually talking about?
Well the 15 psi speaks for itself; at a design pressure of 160psi your iron headed engine is about maxed out, pressure wise.
An extra 6*of cam advance or ~9 psi psi will require best gas or more, and very likely special timing precautions. If you get into detonation, you will lose power. If you retard the ignition timing you will lose power. If you install thicker head gaskets you will lose power.

Still at a design of 160psi, if you cam comes in at 4* retard and you lose 6psi, you can make the switch to a lower octane gas alrighty, but at 156 psi the entire low-speed operating range will lose power, while the top end will be extended slightly, and you might pick up a few ponies, maybe up to half a cam's worth at most.

But here's the thing;
If you have engine tuning issues, and you have installed the timing set dot-to-dot, you have no idea where your cam-timing is, nor if it is the root cause of your tuning issues, or not. If you don't keep the cam-timing in the back of your mind, you might spend hours or days chasing your tail around and around.
I went thru that once with the Mopar 292/292/108 cam, and after moving the cam several times, I just got rid of it.

Having said all that:
if your engine is already assembled, installed, and it tuned ok, then forget about it. From tuned ok, to runs like a raped-ape, will not usually be found in the cam timing.
If anything, run a compression test.
 
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Say you put it together without putting a degree wheel on it. Start it and somethings off. You go through all the easy external things and you sit and stare at it, cursing yourself because you don’t really KNOW and you know what a PITA it is to pull the cover. It’s probably going to leak oil after! You are pulling your hair out!!!! Nope, not me, trust but verify. A friend of mine bought a hemi crank that had the keyway cut in the wrong place. The manufacturer was very leering of selling it, they had a number of them. but as long as you know. Not hard to overcome. Fast forward 10 years and two owners later? That can be a nightmare.
 
Checking the cam timing is usually the difference between "it should run better" and "damn it runs better than I thought it would". I have seen some really piggish rebuilt 440's that need 8,000,000 degrees of timing to run right and the owner swears "she's right here she needs to be, dot to dot".
 
Thanks for all the great information on the cam timeing, definitely haveing my new cam degreed . 340 4 speed. 107 LSA/ 102 CL
..hope it all works out.
 
I just degreed a bbc using a race cloyes 9 key timing set.
The zero mark was off 8 degrees retarded!
And almost all the advance keyways in the crank gear made it retard even more!
So just to check it
I put the gear on backwards in the advance 8 degree position that put it right where I wanted it.
I called cloyes, they said they were aware of some sets that were marked incorrectly.
He would have replaced it, but I liked the overall quality of the gears and chain and the tension of the chain, and I thought what if the replacement is the same or worse!
it took using a 4* degree offset key along with the 2* retard keyway to get it advanced the correct amount.
That took a ton more time then it should have.
But at least I know where the cam is installed.
ALWAYS DEGREE YOUR CAMSHAFT!
 
Maybe I have just been lucky. I have built quite a few engines in my day, and I have never degreed a cam. I have never had a problem, and every engine ran great. My current 340 is probably at least 75HP over stock, and it runs really well with a 'straight up' cam in it.
 
harrisonm said:
Maybe I have just been lucky. I have built quite a few engines in my day, and I have never degreed a cam. I have never had a problem, and every engine ran great. My current 340 is probably at least 75HP over stock, and it runs really well with a 'straight up' cam in
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How do you know its " Straight up?"
If you didn't degree it?
Dot to Dot doesn't mean Straight up.
Like the example I posted,
When I put it Dot to Dot it was 8 Degrees Retarded!
Most cams come with 4 Degrees of Advance built in, so in a Perfect World
Dot to Dot will be 4 Degrees Advanced from the LSA. (Ex. 110 LSA in at 106*)
Straight up means there's No Adv. Or Ret.
It's the Same number as the LSA.
with all the quality control problems,
Stack Tolerances...ect.
just lining up the dots rarely comes out right.
Sure it'll run in Most cases, But at its best or the intended use, Probably not.
 
I installed a cam dot to dot, and then checked the cam timing. It was off by more than 10 degrees (I don't remember how much but a 10 degree bushing would not correct it) from the grinders intake centerline. Had to "jump" the timing sprocket one tooth, and then bring the timing back with a offset bushing. The car didn't run as good as I thought it should. After looking at everything else, I decided to try a different cam. The only thing I changed was the cam. Kept the same timing set. The new cam fell in dead nuts to what the cam grinder said it should be at dot to dot and a "zero" bushing. Car ran much better. One of these days I will check the other timing events on the "bad" cam.
 
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