How to degree your L-series cam....

[BRAAP]

I was asked via PM to describe in more detail what a degree wheel is and does, so I took the liberty of using a current mildly hot N/A L-28 build that we are building here at Rusch Motorsports to use as the example, but substituted in arbitrary cam specs for clarification. For those of you reading this to learn how to do this on your own engine, do not use the cam specs listed here, these specs are for an arbitrary Turbo cam, and yours will most certainly be different.

If you are going to be degreeing the cam, Those “shiny” links on the timing chain and the notched cam sprocket should only be used for installing the cam so that the valves don’t crash into the pistons, not for timing the cam, especially for aftermarket cams as those marks no are pretty much worthless as I am sure the cam grinder isn’t going to grind the cam for all those marks and the planets to line up, they intended for the end user to actually degree in their cam using a degree wheel.

Also, when taking all measurements with the dial indicator, remember to always take those readings rotating the crankshaft in the same direction every time, and that direction should always be in the direction of engine rotation while it is running, i.e. facing the front of the engine, the crank rotates clockwise.

1) Tools needed….You will need a degree wheel, (top pic), a way to mount that degree to the crank snout. You will need a pointer of some sort that can be attached anywhere on the front of the engine but can reach the degree wheel. I use a piece of coat hanger, one for L-series and one for SBC engines. You will also need a dial indicator, (second and third pic, note the steel plate on the bottom right…), I use a mag base mount for my dial indicator and just bolt on a piece of steel plate on the head to hold the dial indicator over the valve to be checked. I typically compress the dial indicator.500” with the valve on its seat. You will also need a piston stop, (see bottom pic), and you will need your cam specs.

2) After you get the degree wheel attached to the crank snout, you will need to positively identify TDC. Do NOT trust the TDC mark on the damper used for timing your ignition. You cannot trust it to be 100% accurate and if the inertia ring has spun, it will be WAY off, and the damper should be thrown away. Using this method to find TDC, you can verify that your damper inertia ring hasn’t spun. Also, if your timing pointer is off a little bit, you can even slot the timing pointer tab to be dead nuts on as well. Rotate the crank so that you know for sure the #1 piston is NOT at TDC. Insert the “piston stop” into the spark plug hole far enough that you know the piston will contact it on its way up the bore before hitting TDC, (see fourth pic “ABOVE”). Now slowly rotate the crank till the crank stops, that will be the piston contacting the “piston stop”. Do NOT force the piston any further up! Set the degree wheel to “0” degrees TDC at this point without rotating the crankshaft. (See the top pic BELOW). Now rotate the crank the other direction till it contacts the piston stop again which in this case ended up registering 57 degrees. (see second pic down.) Half way between this point and “0” on the degree wheel is ACTUAL TDC, which is 28.5 degrees in this example. Now remove the piston stop and rotate the crank too that 28.5 degrees, (see third pic down), and now carefully readjust the degree wheel to read TDC without disturbing the crankshaft. If you feel that you accidentally moved the crank even in the slightest, then start all over again. When you are finished, you will be at TDC referenced by the fourth pic down.

3) Now with TDC being set, the dial indicator set up on the head in contact with the valve retainer to be measured, your manufactures cam card handy, you can degree in your camshaft. There are several ways to approach this. The most popular ways being the “intake centerline” method, the “lobe separation centerline” method, “intake closed at the .050” point” method and others. Most engine builders agree that of all the valve events, (intake open, intake closed, exhaust open and exhaust closed), that the intake closure point is the most critical. There isn’t enough space nor do I have the time to go into the details of why that is in this post. I’ll save that for another post. For this example, I’ll use the intake closure at .050” valve lift as it will be accurate enough for 85% of the projects being built. The “Intake centerline” or “lobe separation centerline” methods are more accurate, but is also more involved. For the this arbitrary cam, the intake closure point at .050” lift is 72 degrees “After Bottom Center”. So, rotate the crankshaft in the direction of engine rotation till the intake valve is on the closing ramp and when the dial indicator reads .050” from the valve being on its seat, the degree wheel should read 72 degrees ABC, (see pics below). If the cam timing is within a couple degrees of manufactures suggested, the engine will run just fine and you wont be able to “feel” any difference, though you might be able to actually measure the difference on a dyno, and depending on the engine package as a whole, may perform better in the range you intend to drive with other than manufacture suggested cam timing specs.

The processes involved in degreeing your cam can be taken to several levels of extreme. There are engine builders that will take into account bearing clearances on the rod journals with oil pressure present, heated block and internal parts when finding TDC, etc. Before you go to such extremes, you have to ask yourself this…Are you building a Nextel cup engine, Formula one engine, Indy car, or just a hot L-series that if the cam timing is off a degree or 2 you wont feel or notice it anyhow?....

That is your quick Rusch Motorsports tutorial on how to degree your L-series cam. Hope this helps…

[beandip]

Paul, Thanks vary much . This post should be in the Technical section. Other wise it will be berried in a day or so. Gary

[g72s20]

Thankyou Paul,

This is a must for any do-it-yourselfers around here, and there is nothing like good photos to show just what is going on.

Thanks again!

Jim.:classic:

[BRAAP]

Paul, Thanks vary much . This post should be in the Technical section. Other wise it will be berried in a day or so. Gary

Gary,

By “technical section”, do you mean, “car forums” “S-30 Z series” “Engine and drive train” section?

HybridZ has been our home for several years, (recently just found this forum), and I have written many other very in-depth tech articles and how-to’s regarding the L-series that I’m sure would be of benefit to the guys and gals on this forum as well.

Thanks,

Paul Ruschman

[Gav240z]

Hi Paul, thanks for the article really appreciate you taking the time to place it on the forums. I have been actively reading your posts on hybridz.org for some time however I haven't posted much on hybridz.org just yet.

There is a section of this site dedicated to technical articles, which I believe is reviewed by the admin not 100% sure since I've never posted a how-to.

[BRAAP]

Glad my massive consumption of band width has been beneficial. Thank you.

As for the Technical forum here… Hmmm. The only forum I could find with the word “technical” in its title is this one. If there is another one, could one of you guys please link me to it?

Thanks,

Paul (possibly blind) Ruschman :-)

[Zedrally]

Hi Paul,

http://www.classiczcars.com/forums/forumdisplay.php?f=129 is the location.

From memory it was locked by the moderator to keep the forum un-contaiminated.

MOM

Edit: Look like the mods have moved it for you....