OK,

Threw this over to the people at pro-touring and they either didnt care or couldnt figure it out. So thought I would test the knowledge of this board. I am trying to determine what the cam specs are on the cam in my engine. It is NOT STOCK and the last owner doesnt know what is in it. Someone said you can figure out the specs using a degree wheel and some math. Would love to know how to do this without ripping the motor apart to get to the cam, pulling it out and reading the number off the back of it. Anyone know how to determine the specs? COME ON, KNOW SOMEONE ON THIS BOARDS GOTTA HAVE THE KNOW HOW.

Thanks in advance.

Mark

not hard... Attach a degree wheel and zero the pointer to tdc. (need directions for this, too?)
Stick a dial indicator on the head, with the pointer on the pushrod side oil hole in the #1 intake rocker, zero it. (if the intake is off, use the lifter.)
turn the engine till the intake starts to open and the dial reads .050" note the reading. Turn till the dail indicator peaks and starts down, that peak reading was your lobe lift. Lobe lift x stock rocker ratio is your gross lift.
Keep turning to .050" closing and note.

Add (360 minus opening reading) to the closing reading, that's your intake duration at .050".

Intake centerline is 1/2 duration minus (360 minus opening reading)

Move the dial indicator to the exhaust and repeat.

Now you know duration and lift & intake and exhaust centerlines. To figure lobe separation, subtract the intake centerline from the exhuast centerline.

Was this a test?

Hey JIM M You the man!!! Thanks for the lesson. I really dont want to rip apart the motor if I dont have to. I got a set of trick flow 23 degree heads and am going to be swapping them onto my engine. If the cam that is in there is a 268 comp cam, I am very happy and wont have to tear down further. I am hoping I can just do the head change without breaking the pan seal, removing the radiator and so on to change cams. Thanks again for being so thorough. I probably will find out the cam I have without pulling the intake.

OK gonna ask the obvious. How do I attach the degree wheel and zero the pointer to TDC?

Thanks I really appreciate it.

when you buy a good degree wheel it comes with all the info you need.
FINDING TOP DEAD CENTER

There are three alternative ways to find Top Dead Center (TDC): (1) positive stop, (2) dial indicator, or (3) positive stop through the spark plug hole with heads installed. Bolt a pointer to cylinder block. If cylinder heads are removed, use either a positive stop or dial indicator.

Find approximate highest point of piston travel,and tighten degree wheel with TDC (0) mark in line with pointer. Then, securely mount positive stop or dial indicator to top of block. Rotate engine clockwise until piston touches. Stop. Check readings on degree wheel.

Then rotate engine counter-clockwise until piston touches. Stop again. Check reading on degree wheel. TDC is halfway between the stop readings. If preferred, use specific dial indicator reading on a dial indicator to obtain the same result as using a positive stop.

The method used with cylinder heads installed is accomplished by using Tavia's #08065 or #08068, adjustable Top Dead Center Stop. Screw it into the spark plug hole so that it will extend ½". Then follow the procedure used with positive stop method.

CHECKING CAMSHAFT TIMING

Install camshaft, timing gears, timing chain, and align timing marks in usual manner using factory timing marks. Install pointer and degree wheel. Find TDC using one of the three methods described above. Insert intake and exhaust lifters for cylinder being checked. Mount dial indicator (or an indicator with 1" of travel recommended) securely to the cylinder block, keeping indicator stem aligned with travel of lifter.

Starting with intake lifter, rotate engine (using flywheel or flywheel end of crankshaft, so as not to disturb degree wheel), until lifter is on heel of cam lobe or all the way down. Set dial indicator on top of lifter, compressing stem of dial indicator at least .020 of travel. Adjust dial so needle points to "0".

Rotate engine in normal running direction until dial indicator needle reaches checking clearance or tappet clearance recommended by camshaft manufacturer (usually listed on timing card supplied with camshaft). Note reading on degree wheel. This should correspond with the manufacturer's intake opens specifications.

Continue rotating engine in same direction until dial indicator reaches checking clearance (lifter in closing position). Note reading on degree wheel again. This should correspond with manufacturer's intake closes specifications. Exhaust lifter timing should be checked following the same procedures.

If readings do not correspond with manufacturer's specifications, repeat complete procedure. If readings repeat, correct timing by the use of off-set cam bushing or off-set key, depending on make of engine.

Keep in mind, the degree wheel is only as accurate as the person using it, and proper camshaft installation requires proper degree wheel use.


OR USE THIS METHOD:


Step 1. Align the timing sprocket dots for straight up. The cam sprocket dot should be at 6 o'clock and the crank sprocket dot at 12 o'clock high. [This is the easiest way to get the sprockets aligned because they are close to one another. It can als be performed with both at 12 o'clock.] Use a straight edge to help with the alignment. Take your time. When the crank key and sprocket and cam key and sprocket are in proper position slide both toward the engine in matching increments. At some point, the tight fit will require taping with a plastic hammer. Light taps... alternate between the crank and cam gears and avoid hitting the chain. If the gear is too tight a fit to start, heat the gears and chain in the oven. Raising the temperature to 130 degrees will make a big difference. Also, put a light coating of anti-seize on the cam hub and crank hub. This will aid assembly and permit removal if you need to pull the assembly apart to advance or retard the cam.[I used a true roller timing set. with 3 key ways; the sprocket was installed on all three to verify the accuracy of the set. It proved to be accurate on all keyways. I chose the middle keyway to give me the 106 degrees specified by Comp Cams. Note that the 270H and other Comp Cam grinds are manufactured with 4 degrees advance. Lobe separation angle is customarily 110 degrees with these grinds.] Once the sprockets are in place, double check the dot alignment by rotating the crank a few times to verify alignment. If everything checks out, proceed to Step 2.

Step 2. Hook up the Degreeing Wheel. Put TDC at 12 o'clock noon and fasten it on with the crank bolt. Also pick the right timing cover bolt hole to fasten your "coat hanger wire" degreeing wheel pointer. After cutting an appropriate length of wire, sharpen one end on a grinding wheel (or use a file) as this will provide an accurate pointer. Bend the wire so that it is at or near the 1 o'clock position on the crank. With my method, the wire will be repositioned several times. Go to Step 3.

Step 3. The piston stop. If the heads are on the block you must use a piston stop through the spark plug hole on the # 1 cylinder to locate TDC. [A spark plug piston stop requires a different procedure--not described here.] If you are rebuilding your engine or have the heads off so that you can see the pistons, a top of the block piston stop will be requred. These stops can be purchased from Crane, Comp Cams, Jegs, Summit, Powerhouse and local speed shops or simply fabricated from a piece of 3/16 inch steel. The steel strap must have three holes drilled into it. Two at each end to secure it to the head, and one in the middle. The stop will be positioned across the top of the cylinder bore and secured with the 5/8 inch head bolts with locking nuts. A whole in the middle of the strap should be fitted with a smaller bolt, e.g. 1/8 inch bolt with nuts and washers. Position the small bolt so that bolt head will contact the top of the piston. It is wide and will not mar the piston surface. Once the top of the block piston stop is screwed in with the bolt head protruding into the bore you are ready to find top dead center (TDC).

Step 4. Finding TDC. Rotate the crankshaft clockwise until the piston stops against the bolt head. Next, reposition the wire pointer to TDC on the degreeing wheel. Be accurate. Then, rotate the engine counter-clockwise (opposite direction) until it stops against the bolt head. Examine the pointer and compare it to the numbers embossed on the degreeing wheel. Divide the figure in half. [Example: degree wheel shows 32 degrees. Half of that sum is 16 degrees] Move the pointer to the half way point between the number and TDC on the wheel. [The pointer will be positioned to16 degrees.] Now, if your calculation is correct by turning the crank the opposite direction, clockwise, the stop should be on same number on the other side of TDC. [The piston should stop at 16 degrees]. If the two integers [e.g., 16] are the same you have found TDC. Now, remove the piston stop and turn the crank until TDC on the degreeing wheel aligns with the pointer. Do not disturb the pointer. [I also verified TDC by using a dial indicator on the number 1 cylinder.] Once you are certain that you have located top dead center, proceed to the step 5.

Step 5. Maximum Lift and Intake Centerline. Install an unoiled hydraulic lifter on #1 intake. Set up the dial indicator so that you can measure the amount of lift on the lifter. Everything needs to be perpendicular and properly aligned. The indicator shaft should sit on the lip of the lifter (not in the cup). Once this is properly aligned, rotate the crank clockwise until the lifter is on the bottom (base) of the cam lobe. This is the lowest point so the dial indicator can now be set to 0. Begin rotating the crank until you reach maximum lift (.313 on 270H). At maximum lift, reset the dial indicator to 0. Now rotate the crank in the opposite direction, smoothly and very slowly, stopping at .100" below maximum lift. Now, reverse rotation until the dial indicator reads .050" before maximum lift. Take a reading off the degreeing wheel and mark that number on the wheel (or use masking tape and write it down on the wheel). Continue rotating the crank past maximum lift until you reach .050" below it and stop. [You are taking readings on both sides of the cam lobe.] Read the wheel and note the number of degrees. Take these numbers (example, 1st reading, 62 degrees; second, 150 degrees ) and add them (62+150=212). Divide this number in half (212/2=106) and you will have confirmed the intake centerline (106). [Additional note: Go through this procedure twice to verify your numbers. Accuracy takes practice. For additional information on degreeing cams, consult the cam manufacture's degreeing instructions.]

[ 02-11-2005, 05:18 AM: Message edited by: dawg ]

Not sure if anyone else has mentioned this yet, but you need to use a solid FT lifter, not a hydraulic. A hydraulic will compress and throw your measurements off. When using the solid FT lifter make sure you set the lash at .000"

I would check .050" lift, but also check duration at .200" lift and duration at .006" lift. There are lots of cams with the same .050" lift -- the extra data points will help you nail down the correct lobe. The .006" measurement will be very close to the advertised duration number.

yes that it right
solid lifter is a must

A solid lifter is a good idea if you have one, but not necessary. If you set the dial indicator on the outside lip of the lifter it's a solid piece of steel and has nothing to do with the hydraulic part of the lifter.

Also don't forget that the NO. 1 intake is the second lifter in from the front. I had brain fade when doing the same thing you are doing and did the whole process three times. I kept coming up with 96 deg lobe center, and knew it had to be wrong. Then I noticed I was using the exhaust lifter..

Jack

if the engine is together, and the lifters are pumped up, on top of the pushrod will work fine. The itty bitty spring in the dail indicator won't compress the lifter.

I agree it couldn't be pushing more than an inch pound.

jack

or go to performancetrends.com and click on cam analyzer.