How To Set Cam Timing On Chevy 350

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Perfect Timing

The Nuts of Degreeing in a Camshaft

You just opened the box containing that new monster cam you bought for your hot rod and y'all tin can inappreciably wait to simply slide that babe in place. Piece of cake, y'all reason. It's going to brand your auto rump and shake like a Pro Stocker, and it's certain to produce more power than any other machine on your block. But is installing it actually a no-brainer? Non exactly. If yous install the cam correctly the starting time time, you will reap all of its rewards. If you don't, you'll exist driving a heap. How do y'all know if it'south installed correctly, you ask? Well, you can either rely on your keen ability to "see" within your engine and "read" the cam'south figures as they actually occur. Or you can degree it.

Degreeing a cam is a simple and effective way to ensure you've got the cam you were looking for and you've installed it correctly. Even with today'south cam companies using some of the best estimator-controlled cam grinding equipment available, in that location'southward notwithstanding the chance for operator error. The cam grinder could take machined the wrong lobes, or the packaging section could take put the wrong characterization on the box. Either fashion, you'd never know unless y'all degree the cam.

In that location's ofttimes defoliation almost what degreeing a cam really means. In its simplest definition, degreeing the cam is a ways of verifying the installed position of the cam relative to the crankshaft; i.eastward. "avant-garde, retarded, or direct-up," and it'south also a style to confirm that the cam was ground correctly. Degreeing a cam is non the aforementioned as advancing or retarding it as some people mistakenly believe. Degreeing the cam involves bolting a precisely-marked bike onto the crank or damper, which volition indicate crankshaft position, and so checking the cam lobes at a specified lift. Nearly caste wheels are numbered in 180-caste increments moving away from both sides of Top Expressionless Center (TDC). Although there are other ways to mark the degree wheel, such as 360 degrees from TDC and also in 90-degree increments, wheels marked 180 degrees on either side of TDC are generally the easiest to use.

FINDING TRUE TDC

This is the near important part of correctly degreeing your camshaft and if it'south not done properly, your results will be worthless. Fortunately, it's also the simplest part of the procedure. Start with the No. i piston approximately at TDC. This can be done past placing your finger over the No. 1 spark plug hole and turning the crank clockwise until air pushes out. Watch the damper for the TDC or 0-caste marking to come upward and end rotating the engine when TDC is indicated on the damper. Install the degree wheel and align a fixed pointer (coat hangar wire works well) with the TDC mark on the caste wheel mounted on the creepo snout or damper. Don't worry about getting it verbal nevertheless, that step is next. Now turn the creepo counterclockwise until the wheel reads about 90 degrees and thread a positive piston stop into the No. ane spark plug hole or strap a piston finish on the deck if the heads are off. Carefully plow the crank clockwise until you experience the piston touch the terminate. It helps to have a hole drilled in your piston stop to bleed off cylinder force per unit area every bit the piston moves up the bore. With the piston touching the stop, mark the degree cycle or write downward the number, i.east. 64 degrees. Next, reverse direction and rotate the crank counterclockwise until the piston touches the finish again and mark the cycle or write down that number, i.e. 70 degrees. The difference between these two readings is six degrees. Motion the wheel or wire half that distance (3 degrees) to indicate 67 degrees on the cycle. Switch direction again and rotate the crank clockwise, and if you lot did it right, the bike should point the same number when information technology touches the piston stop in either direction, i.e. 67 degrees in this case. One time you've got it stopping on the same point in either direction, the bicycle volition correctly indicate TDC with the piston stop removed. Practise Not Motility THE WIRE OR WHEEL AFTER THIS POINT.

THE EASIET METHOD: CHECKING LOBE CENTERLINE

There are two common ways to degree a cam. The easiest is the lobe centerline method. With this method you tin can find out if you've installed the cam correctly and, to a certain extent, check to run into if the manufacturer's grind is right. Without changing your degree wheel or pointer position, rotate the engine until you run across no move on the No. 1 intake lifter, pushrod, or rocker arm. Use the longest ratchet or breaker bar you can when turning the engine for shine movements. Brusque ratchets lead to jerky motions and inaccurate readings. You'll desire to install a i-inch dial indicator reading off the No. 1 intake lobe of the cam (2nd lobe in from the front on the commuter's side of the engine). If your engine is fully assembled, it's easiest to use a pushrod every bit an extension for your indicator (see photos). You'll also need to use a solid lifter lubricated with engine oil merely on the intake lobe; hydraulic lifters cannot exist trusted to read correctly. Turn the crank clockwise until the indicator reaches maximum lobe lift. Zero the indicator at max elevator bespeak and rotate the engine clockwise ii total revolutions to check that the guess returns to zero. If it does not return to zero, check your indicator/pushrod alignment to be sure information technology is not bounden. Starting at cipher, reverse direction and rotate the engine counterclockwise slowly until the indicator passes 0.050. Stop around 0.090 (this step will eliminate any chance of timing concatenation slack affecting your readings) and switch management to clockwise rotation. Slowly turn the creepo clockwise, watching the indicator and stop when information technology reaches exactly 0.050. Write downwards the reading on the degree wheel, i.e. 64 degrees. Go on rotating clockwise until you encounter the dial indicator reach zero and starting time moving over again towards 0.050. Slow down and stop exactly on 0.050. Write down this reading as well, i.east. 151 degrees. Add these two figures and separate the sum by two (64 + 151 = 215/two = 107.5) This indicates your installed intake lobe centerline position. If this figure closely matches (+/- 1 caste) the intake lobe centerline indicated on the timing card that came with your cam (i.east. 108 degrees), it is installed correctly. If it came up higher, say at 112 degrees, you've installed the cam retarded (4 degrees in this instance) or if the figure is lower, say 104, you've installed the cam 4 degrees advanced.

If your figures indicate that the cam is advanced or retarded and y'all take correctly aligned the marks on the timing gears showing the cam to be installed at "naught" or "straight up," then the cam was footing slightly off and you can right its installed position a number of ways. The easiest is by repositioning the crank gear of an adjustable timing chain set. Or you tin can drill the cam gear's dowel-pin hole and install outset bushings to adjust cam position. Of course the easiest method is besides the most expensive, but if you run a belt bulldoze, you lot can speedily and repeatedly adjust the cam position at any time, without getting messy.

CHECKING AT 0.050 METHOD

What the Intake Centerline Method cannot tell you is if the cam's duration was correctly ground at the factory. Although, if the lobe centerline came upwards exactly as the cam card called for, you tin can bet that it was ground correctly. If yous feel the demand to check further, do not change the position of the degree wheel or arrow. Rotate the engine clockwise until y'all see no movement at the lifter or pushrod. Zero it at this point, which is on the cam's base circle. Rotate the engine clockwise and stop exactly at 0.050 and take a reading on the degree wheel, i.e. 12 degrees before top expressionless center (BTDC). Go along rotating clockwise while counting the number of revolutions the indicator makes. Stop when max lobe lift is reached, usually betwixt 0.300-0.400 inch (3-4 revolutions on a i-inch indicator) and have a reading, i.due east. 0.312, to compare the lobe lift figure on the cam card. Keep turning the crank clockwise and count the number of revolutions the indicator makes. Tedious down after it passes zip on its final revolution and end at 0.050 exactly. If you miss 0.050 on the way downwards, stop and rotate counterclockwise past it to around 0.090 and then switch to clockwise rotation once more and stop at 0.050. Accept your concluding reading hither, i.e. 46 degrees after lesser expressionless middle (ABDC). Compare these figures to the cam carte du jour to come across if it was ground correctly and if you've installed it properly.

What if the cam was installed two degrees avant-garde or ground incorrectly? The readings would then exist every bit follows: xiv degrees (12 + 2 = 14) BTDC and 44 degrees (46 - 2 = 44) ABDC. The figures moved 2 degrees, only still have the same overall elapsing. Recollect that when you're degreeing a cam, you're actually reading degrees of crankshaft rotation. So if you lot advance the cam, the valves open up and close sooner in relation to the crank's position, and they open and close later on if you retard the cam.

Full duration at 0.050 tin can be calculated by adding the sum of your ii readings (12 + 46) or (14 + 44)--both equal 58--plus 180 degrees for crankshaft rotation because the cam spins at half the creepo's speed. This equals 238, which should lucifer the "duration @ 0.050" figure on the cam card. If this effigy is off past less than two degrees, don't worry, unless yous're a perfectionist. It won't even exist noticeable in the car.

HOW DO YOU READ THAT?

Degree wheels come in many dissimilar sizes, just they all take the aforementioned shape--round. They can be marked in several ways, with the most common being 180 degrees away from TDC as shown. Marking in this manner makes readings more sensible when degreeing the cam. Some of the professional wheels are marked off in 360-degree or xc-degree increments. These types of wheels look cool and are normally a much larger diameter lending to more accurate readings, but also require more than math to use and should be avoided past the occasional cam degreer.

Wheels like this Crane/Cam dynamics unit of measurement pictured also have shaded areas indicating lobe centerline, intake opening/closing, and exhaust opening/closing. All these areas assistance to more easily place the position of the cam so your readings don't become confused. Expect closely and you lot'll besides notice that the bottom one-half of the bicycle is numbered away from BDC on its inner shaded ring. This area is conspicuously marked as "intake closing-ABDC and exhaust opening-BBDC." This particular wheel also includes several useful cam-degreeing formulas right on its face. These formulas help y'all calculate overlap, intake and exhaust duration, intake centerline, and exhaust centerline.

Source: https://www.motortrend.com/how-to/0105sc-degreeing-camshaft/

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