Why degree camshafts

Its purpose is to operate the intake and exhaust valves in the correct timing with the piston as it sequences thru the four strokes. In the old days, the first four cycle engine had very short valve timing, but rightfully so because these were slow speed engines. The engineers of the late 's were only concerned with harnessing power of the gasoline and air explosions in an internal combustion engine to propel an automobile, hopefully, a little faster than a horse.

They were merely concerned with getting the engines to run at slow speeds. Even in their wildest inspirations they would never have believed that a quarter or half century later, with better structures, these same engines would be revved five times as fast and produce many times more power.

The old valve timing then was: Intake valve opens at T. Also, the exhaust valve opens at B. The burnt gases, due to their high pressure, virtually expel themselves, and the piston drives the last of the gases out; the exhaust valve closes at T.

These early engines had Oo overlap or no overlap whatsoever. By experimentation, the more progressive cam engineers of the 's and 's discovered that the midrange and high-speed power could be greatly improved by lengthened valve timing. The stretching of the intake valve timing allowed the engine to breathe deeper and take in greater amounts of air and fuel, thus creating a more powerful explosion in the combustion chamber.

An important advantage gained from lengthened valve timing is that the greatly expanded gases are eliminated more efficiently and virtually by their own pressure.

Lengthening of valve timing in the gasoline engine brought on accidental overlapping of the intake and exhaust valve events. Both intake and exhaust valves are slightly open at T. In the early days, this unintentional overlapping was at first considered detrimental. But much later, it was discovered that a mild scavenging effect was obtained from the overlap event when the exhaust actually pulled some of the intake charge in.

In the early 's, Iskenderian introduced the first long duration cams which took full advantage of an extra long overlap period to super scavenge the combustion chamber and create in effect a fifth cycle in the four cycle engine. This is purposely done to give the relatively slow opening valve a head start on the piston so at T. As the piston reaches and passes T. The burnt exhaust gases in the header pipe contain a great deal of column inertia.

At high engine speeds, a noticeable scavenging phenomenon occurs when this column inertia actually helps draw in the intake charge during the short overlap period. Had the intake valve been prematurely closed at B. Some 70 degrees after B.

Just before reaching T. As the piston reaches T. This seemingly loss of useful power is offset by the fact that the hot exhaust gases now leave the cylinder by virtue of their own pressure, thereby reducing the effort on the engine's part to expel the burnt gases on the upward stroke of the piston.

The piston completes its descent and once again rises in the cylinder to continue the exhaust stroke. Some 30o after reaching T. This completes one sequence of the 4 strokes. You should now understand the relation of piston movement to valve operation and are ready to learn the procedures for checking valve timing Cam degreeing. Because Iskenderian Cams are manufactured with such high precision you can install them on the stock timing marks without any further checking; however, for those who wish to learn how to properly check and verify valve timing, we recommend the following procedure.

The purpose of checking or degreeing-in the camshaft in the engine block is to determine whether or not the camshaft is installed in the correct relationship or phasing with the crankshaft. However, the most important step in phasing a camshaft is finding absolute T. Trying to operate an engine without this vital marker is like trying to read a tachometer without an indicator needle. The T. Quite often, we have observed racers at Bonneville, drag strips and circle tracks who neglected to provide themselves with a T.

All stock engines have a stationary pointer affixed to the block, and a T. But, these racers lost the original pointer when they changed to an aluminum timing gear cover. Or, on supercharged engines, when they changed to a steel crankshaft drive hub, they lost the original T.

Now, here is their predicament: they now have no way of accurately setting their spark lead or valve timing. Had this engine been accurately calibrated for T.

Thus, a possible winner became a loser. It is a common error to miss T. Inasmuch as this inaccuracy will substantially affect subsequent timing, the following procedure is suggested to correct this error.

Split the difference your error in degrees by moving the degree wheel radially on the crankshaft. After you have made the adjustment, come around with the crankshaft as before, stopping. When you get exactly the same degree readings. NOTE: The exact travel of. Any check point between. The most practical way of locating T.

No dial indicator is required for this procedure. First, let's see how it's done, utilizing the degree wheel. Even without the degree wheel, you can and always should calibrate the T. By using Step No. Squirrel has spoken on this thread. I am sure he will correctly say what I am saying.

Joined: Dec 6, Posts: 1, Profile Page. Don't run gears. I ended up retarding the cam a couple degrees on my Chevy II to make sure I had enough valve clearance. Most street cams have some advance built in. Joined: Sep 22, Posts: 1, Profile Page.

The "Why Do It" question should be answered with the reasons behind camshaft degreeing in. When building a performance engine there is an attempt to reduce all of the variables inside the engine. This includes balancing rods,pistons,maintaining a specific deck height,making sure the head chambers are all the same and more.

Degreeing in the cam confirms that the cam is ground as specified and that it will be installed for the best performance as the builder sees fit. By the use of advance and retard "keys" and other methods to move the cam timing around,maxium performance can be obtained and then also repeated if desired.

Its just another tool to reduce the variables in engine building. Personally I check all of my cams on my Cam Dr machine as I have found some "differences" shall we say in manufactures specs. Hope this helps,Oldmics. Oldmics , Feb 16, Well said Oldmics, that's a great description as why we check cam installation with a degree wheel To see if we got what we asked for or what they specked for us from the cam grinder Joined: Mar 18, Posts: 1, Profile Page.

King ford , Feb 16, I don't think that the novice engine builder or even the more experienced engine builder such as myself has enough knowledge to select the proper cam for a given build. I know a veteran builder who spends endless time on the dino and has tried hundreds of cam combinations for the NASCAR spec late model stock car engines with 2x carb setups. I believe he has by far gotten the most hp out of this combination that I have seen in a long time.

If you ask him what cam to run he probably could get you close but that last 20 to 30 hp that makes the diff can only be found on the dino.

The cam degree fazing is one of the ways that it's found along with many other fine adjustments found only in the dino proses. All these things have to complement each other and one of them out of spec can diminish the end results. Most reputable cam grinders can get you close for your street application if you listen to there recommendations and give them correct info when asking for a cam recommendation.

Competition however is a hole nother ball game and will require the expert dino guy to get all that is available from any combo. Dino tuning is priceless in my book for competition engine building Joined: Apr 12, Posts: 1, Profile Page. Joined: Nov 23, Posts: 5, Profile Page.

There are many here that can probably figure the proper set up in their sleep. For many of the rest of us it's something rarely done. Generally speaking a cam manufacturers tech line is helpful for those that do not do this every day.

Sorry for crappy pic. Joined: Sep 17, Posts: 9, Profile Page. An old tip from Edelbrock Get a set of offset cam keys or bushings and try different advances. Check compression with a compression gauge. Whatever setting gives the most compression will work best for street use, by giving you the most low end torque. Advance the cam for better low speed performance, retard for high speed performance.

You can actually "rock" the torque curve about its mid point this way. Rusty O'Toole , Feb 16, Truck64 likes this. Joined: Apr 28, Posts: 6, Profile Page. The problem with the centerline method is it has you finding the theoretical point of peak lift in relation to crank rotation. This method makes the assumption that the lobe or valve motion you are checking is symmetrical; with its opening side being the exact same shape as the closing side of the lobe.

Most modern cam lobes are asymmetrical, with the opening side of the lobe being much more aggressive and the closing side being gentler. Therefore when you attempt to locate the middle or centerline of the asymmetrical lobe there is an automatic error. Also, the centerline method does not really indicate if your camshaft was properly produced, as no confirmation of the duration at any given point. Our method will verify correct valve opening and closing and duration.

Looking for a more in-depth course on How to Degree a Cam? The High Performance Academy has a courses that covers this specific topic in a huge amount of detail. The lessons are delivered via high quality, online video. Dealer Enquiries. Toggle Navigation 0. Home Camshafts Please select your engine model below to view our range of catalogue camshafts. Chrysler Hemi 6 Cylinder. Ford EE cc 1. Holden Straight Six.

Rover 3. BMW B Harley-Davidson Harley V-Rod. Toyota 1UZ-FE 4. Such as: Cam or crank gears are incorrectly marked. Keyways are out of position on gears. Keyway in the crankshaft is miss-indexed.

Degree wheel 2. Metric or imperial dial indicator and method of mounting it to the head or block 3. Positive stop TDC finding tool either the spark plug type or a block mounted type 4. Rigidly mounted pointer to indicate degree wheel position Mounting the Degree Wheel Attach the degree wheel to the flywheel or to the front pulley of the engine ensuring that you still have a method of manually rotating the engine.

Attach the pointer to the engine ensuring that it is rigid and won't move if you accidentally bump it. Next, adjust your pointer to the zero TDC position on the degree wheel. It is essential at this point that you have some means of rotating the crank that will not interfere with the degree wheel. The crank can be rotated from either the front or the flywheel end.

The greater the leverage, the smoother you can rotate the crank for timing checks. Do not use the starter for turning the engine while degreeing. Now that the Degree Wheel has been set at approximate TDC, and a means for turning the crank provided, you're ready to install and set the piston stop. Turn the crankshaft in the normal direction of rotation to lower the piston enough in the cylinder to move the degree wheel degrees, screw in the piston stop until it contacts the piston, Turn the engine in the normal direction of rotation until the piston comes back up and touches the piston stop.

Make a note of what degree the pointer is on the degree wheel. Turn the engine in the opposite direction until the piston comes back up and touches the piston stop again.

Add these two numbers together then divide them in half. The total would be 36 degrees.