Degreeing a camshaft

[1930]

I have been asking around on different forums but cant seem to get a yes or no answer or am having a hard time interpreting the responses I receive. Maybe I havent ask the question the right way.

Id like to know if it is possible to degree a camshaft without a cam card or grind number for the cam.

I have one in my truck now, I plan to replace it but I would like to play around with it before chucking it, Id like to learn how to get the very most out of the cam, Id like to dial it in with the crank so that it gives me optimal results.

Is this possible with having any more information about the cam other than what I have mentioned above which is virtually nothing other than it fits in my 225 cam journals.

Yes or no answer please.

If the answer is yes can someone get me started on how I need to go about doing this. I have the head on the engine and would like to do what I need to do while it is still on if possible.

 

[krazykuda]

Yes, you can tell what a cam is by degreeing. It is the only way to properly tell what a cam is because some manufacturers measure their cams differently. lIt's going to take me a few minutes to write it up for you.


The best way to compare cams is to degree them yourself, so it is measured the same way and is "apples to apples"...

 

[krazykuda]

Ok, the first thing to do is to find top dead center (TDC). This is the highest point that the piston reaches in the stroke.

Mount a degree wheel on the crankshaft/vibration damper (you may have to remove the pulley). Make an indicator out of bending a steel wire coat hanger and use another open hole nearby to mount it.

Then get a dead stop tool that fits through the spark plug hole and you can screw another (inside screw) down a little bit. Then turn the engine over slowly by hand until the piston hits the dead stop tool. If if doesn't stop, then screw the inner screw down a few more turns until you can. Then record that reading from the indicator that you made for the degree wheel. Reverse the crankshaft now until it hits the stop tool again and record the readings. Average those two readings and that is your TDC.

Now reset your degree wheel or indicator to read "0" at TDC on the crankshaft. DO NOT LET THE DEGREE WHEEL MOVE AFTER THIS OR YOU WILL HAVE TO DO IT OVER!

Congratulations, you have now found true TDC!

 

[Darter6]

If it is stock, factory, you may be able to get the specs you need from a factory service manual for your make and model.

 

[pishta]

To find cam duration, use dial indicator and zero out on puhrod. turn until the pushrod starts to move and note when it hits .050 on the upstroke, note degree wheel value, keep turning and look for .050 on the downstroke and note value . Take total crank duration between .050s and that's your duration of said lifter, intake or exhaust. You can now find centerline as you know duration, devide by 2 to get opposing intake/exhaust lobe centerlines, and now you can use one centerline to determine lift at cam by multiply by rocker ratio to get valve lift. Iirc, the duration is like 240 on a stock six intake, very conservative when the 'roadrunner' cam was a 284/.484 lift.

 

[krazykuda]

Now you must have the head on and the rocker arms. I would recommend using a solid lifter and adjustable pushrod to measure the cam specs. Install the cam, lifter, pushrod, and rocker arm.

Now set up a dial indicator on the valve spring retainer making sure that you are as close to parallel with the valve stem angle as you can get. Do intake and exhaust valves separately.

Intake:

Turn the engine over for a full cycle and watch your dial indicator. Set the dial indicator to (0) at when the valve is fully closed. Make sure that you have enough travel in the dial indicator to accomodate the maximum lift of your cam or at least .600" if you do not know.

Now turn the engine over until the dial indicator just starts to move. If you can stop just as it reads .001", then stop there and record the reading from the dial indicator ((.001") and the angle on the degree wheel where it is at that lift. You may want to also try to stop at .002", .005", and take some more readings. Definately stop at .050" lift and record that angle on the degree wheel. You may want to record readings from .025" and every additional .025" after that to get a good idea of the ramp speed of the cam.

DO NOT REVERSE THE DIRECTION THAT YOU SPIN THE CRANKSHAFT DURING THIS PROCESS as the timing chain slack may induce some error in your readings. ALWAYS ROTATE THE CRANKSHAFT IN THE DIRECTION OF SPIN WHILE DEGREEING A CAM. Never reverse!

If you pass up a reading, spin the crankshaft two revolutions and catch it on the next time.

Now map the readings as you go back down; .450", .425", .400", .375", .....050", 025", .010", .005", .002", 001", then as close as you can to (0).

Now you can take those readings and find out your cam size. Take the reading from .001" and add 180 and the reading at .001 on the way down. That total is your total or "advertised" duration.

Now take the two readings from .050" on the way up and down and add them together (in some cases you may need to add 180, and some not depending on how big the cam is). Now this is your duration @ .050" which is a standard that most cam grinders use to rate their cams. This is called your duration @ .050".

You now can take the duration @ .050 and divide it by 2. then subtract that reading from your degree wheel reading for lift .050" to find the "Lobe Center" or center line of the intake lobe. (Usually somewhere between 114° and 104° after top dead center for most cams). I would not recommend using any readings under .005" to calculate lobe center. You may also recheck by doing the same for any other "set" of points (same lift open as closed) for lobe center to check your accuracy.

Now do the same thing for exhaust valve.

 

[1930]

Thanks very much for everyones comments, I have not yet read all of the posts yet so cant comment directly on specifics but the efforts so far are very much appreciated.

 

[1930]

Thanks again, some more questions, please bear with me....

How does doing this tell me if my cam and crank are in the best relation with each other, in other words assuming that the dots cannot be trusted and I am off one way or another a tooth +.

As far as what I am reading above it has been explained to me how to measure the camshaft to see what the specs are which is info I plan to use now.

I may be mistaken but I thought the term degreeing in a cam meant to get the cam and crank in optimal relation to one another so that the vacuum pump ( engine ) operates most efficiently with peak vacuum/exhaust.

Also my engine is 1986 hydraulic engine, it is recommended that I get a solid lifter and pushrod which is easy enough for me cause I know of several early slants in salvage yards but would pushrod length be the same/does it matter and would using a used solid lifter from a different engine be Ok to do considering it hasnt been worn in too match my cam?

BTW in case its not known I am having very low vacuum readings on my newly re-built engine, at this point we are believing it is due to cam and crank not being aligned properly regardless of where the dots are lining up so this is where I am at with my attempts to figure what the heck is going on.

I plan to get a different cam, not sure yet what I am going with, either a re-grind or a custom grind or an off the shelfer.

I also plan to get a higher quality timing set, at this point though taking my time and learning what I can about these engines and enjoying myself. I am in no rush.