Advancing the camshaft essentially closes the intake valve earlier which in turn makes for an increase in the cranking compression.  This in turn increases the low end torque values.  Whereas advancing the camshaft works well for a naturally aspirated engine, on a boosted engine there is an increase in torque related directly to the increase in filling cylinder pressure.  This increase in filling cylinder pressure increases the torque without having to put additional advance on the camshaft to achieve the same thing as is done with a naturally aspirated setup.  There's actually much more to this but this is the simple explanation.

Lorena, Texas (South of Waco)

Chuck,

Depending on what you plan to do with the engine, drag race or town cruiser, I beleive on a previous post somewhere a couple years ago on the subject, it was stated that Normally advancing the cam will give better low end torque if you want a tire fryer. retarding will give more top end HP in the higher rpm range. Ted or John may be able to explain the scientifics of this.

55 Vicky & customline

58 Rack Dump, 55 F350 yard truck, 57 F100

59 & 61 P 400's, 58 F100 custom cab, 69 F100, 79 F150, 82 F600 ramp truck, 90 mustang conv 7 up, 94 Mustang, Should I continue?

Thanks Ted. I checked the timing marks as you instructed and came up with approximately 2-3 degrees advanced. Some health stuff has slowed down getting the engine fired back up so I have more time to worry and second guess my work.

57 Black Tbird 312/auto

On the overlap stroke, the exhaust valve is closing (coming up) while the intake valve is opening (going down).  Always rotate the engine in the direction it normally runs which is clockwise looking from the front.  There is a point where both valves are equally open and this point would be the split between the intake and exhaust lobe centerlines.  Assuming the camshaft is a symmetrical grind where both the intake and exhaust lobes have the same duration and lift, then the point where both rocker arms are level during the overlap stroke (both valves open an equal amount) will be a good indication of where the lobe centerline angle is.  The damper can then be used to determine how many degrees the camshaft is advanced or retarded depending upon where it sits in relation to TDC on the damper.  This method is not quite as accurate as when using a degree wheel and dial indicator but gets you close enough to realize if there is a major problem or not in the cam timing area.

Lorena, Texas (South of Waco)

Ted,



Could you go into more detail about which rockers; intake or exhaust, and how to move the crank to get this reading? I don't quite understand it. I used a degree wheel and dial indicator when doing my build but being it was the first time doing so, I would like to use this method to recheck my attempt. My engine is in the car but haven't finished enough of the install for the start up. Thanks.

57 Black Tbird 312/auto

If you’re relying on aligning the marks on the gears to time the camshaft and not using a degree wheel and dial indicator to accurately phase in the camshaft, it’s going to be pot luck on where the camshaft is actually installed.  Said another way, “If the camshaft is not setup with a degree wheel and dial indicator, you will not have a clue where it’s really installed other than the marks are aligned”.  Although checking the cam phasing is typically performed on the #1 cylinder, be sure to move the dial indicator that’s being used over to the #6 cylinder and also check both the intake and exhaust lobes.  The degree wheel reads TDC for both #1 and #6 so this is just a dial indicator movement from the tappets on one cylinder to the tappets of another.  If you get more than a 2° difference between the #1 and #6 cylinders on either the intake or exhaust lobe centerlines, do some rechecking.  If necessary check all the lobes on all cylinders.  There are some cams out there that are sloppy in this regard and now is a good time to catch any discrepancies in the cam grinding itself.

 

Also remember that a camshaft ground on 110° lobe centers installed straight up will actually be 110° intake lobe centerline.  This means that the exhaust will also measure at 110° exh lobe centerline.  If the intake lobe centerline calculates out at 108°, then the cam is 2° advanced and in this mode, the exhaust will read 112° exhaust lobe centerline.  The amount the camshaft is ground on doesn’t change but the phasing of that ground lobe centerline in relation to TDC does change. In the 2° advanced scenario, the 108° and 112° being added together and then divided by two still adds up to the original ground 110° lobe centerline.

 

There is a way to approximate what the cam timing is on an assembled engine without the aid of a degree wheel.  Assuming the damper is accurate at TDC, then the rockers on #1 or #6 cylinders can be caught when they are both slightly equally depressed and level (overlap mode) and then measuring the distance from TDC on the damper in degrees.  The damper marks sitting a given number of degrees before TDC would have the camshaft advanced that much while after TDC would have the camshaft retarded.

Lorena, Texas (South of Waco)

The last two "True Roller" sets that I used I had to set them 6* advanved to get them to the specs on the card.

   God Bless.   Tim                           http://yblockguy.com/

350ci Y-Block FED "Elwood", 301ci Y-Block Unibody LSR "Jake", 312ci Y-Block '58 F-100, 338ci Y-Block powered Model A Tudor

tim@yblockguy.com  Visalia, California    Just west of the Sequoias

While we are on the subject, I could use some advice too on my cam set-up. I'm also going to be running a modified VS-57 (SN-93) with about 5 lbs of boost. My cam is an Isky grind#301-S-903. 110 degree lobe seperation,290 degree duration, 0.290" cam lift and 0.435" valve lift. I also have the 9 way adjustable timing set and have never needed to use a degree wheel before, but I'll get one for this set-up if I have too....Way too much time and $$$ to take chances.

Rono

  Ron Lane,  Meridian, ID

Thanks Ted,

I will be setting it up with a degree wheel and dial indicator. I read on the forum that someone found a RPM 300 with a 108 centerline instead of the advertised 112. So I figured I would want to check the specs anyway. If all checks out correctly I'll probably go with the 2 degree advance. Chuck

Y's guys rule!
Looking for McCullouch VS57 brackets and parts. Also looking for 28 Chrysler series 72 parts. And early Hemi parts.

MoonShadow, 292 w/McCulloch, 28 Chrysler Roadster, 354 Hemi)
Manchester, New Hampshire

Chuck.  My recommendation is to install the camshaft either straight up or up to two degrees advanced.  This is best accomplished using a degree wheel and dial indicator.  Don’t rely on the crank gear keyway markings as stackups in the machining variances for the keys at the various locations can add up to a significant amount of error.

Lorena, Texas (South of Waco)