Even sometime MM&FF photographer...
Even sometime MM&FF photographer Justin Cesler, self-described as someone "so awesome that if you met him, you'd puke," couldn't figure out how to degree our camshaft-at first.
If there's an elusive animal in the amateur performance world, then degreeing a cam is it. Few know how to do it, and even fewer understand the benefits.
If you're following our 347 build from the previous issue, then you already know we're assembling a cost-effective, home-built stroker for our SSP coupe. Not long after the short-block was finished, Editor Smith strolled into our well-equipped air-conditioned shop to check up on his sophomore associate editor and the progression of the engine build. He asked if I checked for piston-to-valve clearance (which I hadn't yet), and I replied with a casual, "That's next." His next question caused a lump to creep up my throat: "Did you degree the cam?"
Since I didn't know how or why to degree a cam, it was a great opportunity to not only teach myself (read: call someone with knowledge and experience), but to also relay my newfound knowledge to you, our loyal readers. You can share this knowledge with your buddies and increase your cool factor a degree or two.
So, why degree your camshaft? Well, in bygone days of big "three-quarter race cams," engine builders relied on one-off grinds by less-than-precise cam-grinding equipment. Therefore, you had to index your cam to the proper degree-meaning the intake cam lobe would be in perfect relation to the location of the piston on the intake stroke.
In other words, it's a way to maximize camshaft-timing advance beyond what the camshaft manufacturer includes in the profile. This allows air to begin filling the cylinder earlier, causing better cylinder filling, and allowing more torque production.
Now you know why to degree your cam, but what benefits will it provide?
"Degreeing your cam may add a few horsepower," says Ron Robart of Fox Lake Power Products. "And it can move the power band to a different portion of the rpm range." In other words, advancing the cam in our 347 may give us a little better power curve through the mid-range, but we would lose a little up top.
The bottom line remains the same-degreeing your cam sounds cool, looks cool, and can help you make more power. We're in.
The first step is to determine...
The first step is to determine top-dead center (TDC) and then bolt the degree wheel to the crankshaft.
Though a piston stop is preferred,...
Though a piston stop is preferred, a dial indicator will work fine. Just make sure it's mounted straight and touches the very center of the piston. Rotate the engine a full revolution in both directions to be sure you have achieved TDC, and set the dial indicator to zero.
Fashion a pointer out of some...
Fashion a pointer out of some baling wire or a metal clothes hanger. Bolt it to the block and bend it to point at zero (TDC) on the degree wheel.
Since we didn't know what...
Since we didn't know what we were doing, we called on Greg Lovell of AntiVenom. The Tampa-based shop made its name hating Vipers and building LS-powered race cars, but mostly hating Vipers. Lovell began our lesson by setting our dial indicator atop a solid lifter that was inserted into the lifter bore.
Lovell zeroed the indicator...
Lovell zeroed the indicator and rotated the engine a couple of revolutions to make sure the dial indicator was stable and accurate. Check accuracy by measuring overall lift and comparing it to your cam card.
Lovell then rotated the engine...
Lovell then rotated the engine clockwise until the indicator read 0.006 inch. This is the measurement that our cam card gave us to determine valve timing.
On the intake side, the first...
On the intake side, the first reading should match the opening measurement on your cam card. The close should be equal to 180 minus your second reading. Your exhaust side should be opposite-the close reading should match, and your open reading should be 180 minus the number on the card. Shown here are our open and close readings for the exhaust side.
Our card reads 30 degrees...
Our card reads 30 degrees on the close side, and our degree wheel reads 29 degrees-only 1 degree off. Our open reading is 102. Since 180 minus 102 is 78, that's our reading. This is also good because our card reads 79 degrees. Though off by 1 degree, we're going to call ours straight up. Since we like the cam profile the way it is, we'll give it a chance.
Believe it or not, the next...
Believe it or not, the next step is the easy part. Just pick up an adjustable timing chain set like the one you see here from Comp Cams (PN 3135KT; $191.29). By indexing either the crankshaft gear, you can achieve advanced or retarded cam timing. Once you reinstall the timing set, recheck cam timing until you achieve the number of degrees advance or retard that you desire. Be sure to recheck piston-to-valve clearance when you're done.