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Using a degree wheel to degree in your L series cams

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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.

 

DegreewheelLarge.jpg

 

IndicatorLarge.jpg

 

Pistonstop2Medium.jpg

 

 

 

 

 

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.

 

FindingTDCCustom2.jpg

 

 

 

 

 

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.

 

Intakeclsed050Custom.jpg

 

 

 

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…

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Guest jonnycowboy

Awesome tutorial... I vote this as a sticky!!!

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Great read! Correct me if I am wrong but our cam sprockets don't allow for degree adjustments, it would take a special sprocket to really "degree" our cams. .So would you be just checking to see if you installed the cam correctly??

I did this procedure on my Kawasaki 1000 when I installed Web cams but they had slotted sprockets. This is not a job you just jump into but much to my surprise though, the folks at Web were very helpful and walked me thru the procedure to check my lobe centers.It came down to simple math and reading the dial indicator.

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Great read! Correct me if I am wrong but our cam sprockets don't allow for degree adjustments' date=' it would take a special sprocket to really "degree" our cams. .So would you be just checking to see if you installed the cam correctly??

I did this procedure on my Kawasaki 1000 when I installed Web cams but they had slotted sprockets. This is not a job you just jump into but much to my surprise though, the folks at Web were very helpful and walked me thru the procedure to check my lobe centers.It came down to simple math and reading the dial indicator.[/quote']

 

 

they do make adjustable cam gears for the L series motors. just an extra 300 bucks ontop of what you would initially spend to do it.

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They're not that expensive.

 

The Nissan Comp one is the cheapest I think. It also isn't infinitely adjustable. It has 8 holes and each one is 1 degree different. Gets you close though.

http://www.courtesyparts.com/Merchant2/merchant.mvc?Screen=CTGY&Store_Code=CP&Category_Code=s30_nismo_adjustablecam

 

The Arizona Z Car slotted type, for only ~$20 more. I've heard tell from various racers that you need to keep on top of the bolts and make sure they don't loosen up, but it is the more precise way to adjust it: http://www.arizonazcar.com/sprock.html

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I was fortunate enough to have a very nice degree wheel built into my ATI damper. With the head off, I found the exact TDC with the dial indicator. I then draped the chain on the lower sprocket and fabricated a more rigid pointer out of 3/16 steel rod, grinding the tip down to a nice point. I could then finish installing the head and have a pointer which could take a slight bump and not be affected, which didn’t happen anyways, but it’s a nice insurance policy.

 

100_0047.JPG

 

I also used the t-stat housing for the plate mount. I suppose I could use some flush tapered screws, but the bolt heads really don’t hamper the indicator base.

 

100_0048.JPG

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Hi

I have a 20 mm x 20 mm x 180mm block of cutting board between the chain and curved guide at the moment.

The chain maybe a bit worn but I have also had the head shaved a lot too

Ive got to fix this slack chain some how.

Does anybody know where to buy a custom sprocket setup that sits in place of the cover plate on the front of a L series head?

Ive seen it some time ago on the net but cant find it now.

I have also looked at removing links from the chain

I could buy a smaller chain for a L18 engine and fit that there would be some redrilling of the chain guide etc

 

Help !

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I'm using the Arizone Zcar adjustable gear on mine and have had no loosening of the bolts. I did snug them up pretty tight initially tho. I also turn my car around 7800 between shifts, so I'm sure it gets a work out. The arizona zcar unit is nice and worth the money.

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Since the aftermarket cams we prefer use and sell in our Cam kits are from Rebello, I thought we should also post some details and pics of the Rebello cam adjustment procedure since it is little different than the typical lash adjustment, well, the point where the feeler gauge is used is different, the rest of the lash adjustment procedure is the same as you would use for most other cams including OE.

 

Rebello cam lash adjustment.

Rebello has their cams ground with what Dave Rebello calls a, “tight lash lobe profile”. That just means the lash clearance is a little tighter than what we are used to seeing, and Rebello cams should have the lash checked/set at the valve stem, NOT under cam lobe as most other aftermarket/OE cams are done. The easiest way to do this is using a feeler gauge between the tip of the rocker arm and the lash pad. The trick here is the ears on the top of the lash pad prevents using standard feeler gauges, so unless you have special narrow feeler gauges, you will have to modify a set of feeler gauges just for this using a pair aviation tin snips. Since Feeler gauge sets are quite inexpensive, (can be had for under $10), this shouldn’t be a big deal if you after just shelling out big $$$ for a custom head and Rebello cam kit… (or maybe we could just supply that special feeler gauge in the cam kits that we sell?... Hmmmm..)

 

Here are couple pics of a custom P-90A head we just built for a customer in the UK with his Rebello cam showing where to check/set the Rebello valve lash.

 

 

Lash2Large.jpg

 

Lash1Medium.jpg

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Paul, what is the advantage of this approach to setting the valve lash?

 

Daniel,

 

 

My best guess for why Rebello camshafts need to be adjusted at the valve stem vs at the cam lobe, like most other aftermarket cams, is because the opening and closing ramps of the cam are ground in such away requiring such a tight lash clearance that it is easier to get more accurate lash adjustment at the valve stem than it would be at the cam lobe, (approx 1.5 times more accurate due to the rocker ratio).

 

 

That’s my best guess.

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UPDATE! degreeing a Rebello cam…..

 

 

Since the aftermarket cams we prefer use and sell in our Cam kits are from Rebello, I thought we should also post some details and pics on how to degree in your Rebello cam since this procedure is entirely different than the typical cam degreeing procedure posted above. You will only need a degree wheel to find TDC for cylinder number 1 and to verify that the piston hasn’t moved while degreeing in the Rebello cam and you will need 2 dial indicators. When you first read through this, it may sound complex and confusing, but its not really. After you take it all in, you’ll find that this procedure is really quite simple.

 

First off, I’m going to assume that you already have your timing gear installed and that you set up the shiny links and all that jazz, i.e. the cam timing should be close and the valves “shouldn’t” crash into the pistons while you rotate the crankshaft getting all set up and that you have set your valve lash to the proper specs as well.

 

Now you will need to set up BOTH dial indicators so that each one is resting on an intake and exhaust retainer respectively, (see pic below showing one dial indicator set up as described). Now there are several ways to go about the next step, but this is probably the easiest with the least math involved. Rotate the crankshaft so that bot the intake and exhaust valves for number 1 cylinder are on their seats, i.e. closed. Now “zero” the dial indicators.

 

Next, you will need the number 1 cylinder at TDC of valve overlap, both cam lobes pointing down approx equally. This is the end of the exhaust stroke, beginning of the intake stroke, or put another way, NOT TDC of the firing stroke. (see pic below of both valves open). If your intake and exhaust lobes for the number one cylinder are pointing up equally, then you are on the wrong TDC, just rotate the engine through one more “crankshaft” revolution, (this ends up being one-half cam revolution), and you will be set. Remember, you will need the piston to be EXACTLY at TDC as described at the very beginning of this thread using the degree wheel and piston stop to find TDC.

 

Now with piston at TDC, depending on how your adjustable cam sprocket operates, you will need to rotate the cam WITHOUT disturbing the crankshaft. This is where the degree wheel comes in handy. Keep a close on eye on it to verify that you have NOT altered the crank position or you will have to start over. Keeping an eye on the dial indicators, rotate the cam WITHOUT moving the crankshaft, until both the intake and exhaust valves are open the exact same amount. In engine building speak, this is called having the cam timed “straight up”. At this point you can re “zero” both dial indicators or just leave them alone. I recommend to just leave them alone but do make note of the reading you have on both indicators, (which should be the same on both). For this example, I’m going to use the specs for the Rebello .520” lift cam we ordered for Silent. Dave Rebello recommends for hot street L-series engines using this cam, to set it up between .025” and .030” advanced. “Ok, what the heck does that mean”, you are thinking right?. Well that means that the camshaft needs to be advanced till the intake valve is open between .025” and .030” MORE than the exhaust valve during valve overlap. SO, now all you have to do is rotate the camshaft WITHOUT disturbing the crankshaft, till the TOTAL amount of difference between the intake and exhaust valve opening is between .025” and .030”. You did make note of the dial indicators reading when both valves were open the same height, right? Just checking. This could mean that the intake valve opens up between .0125” and .015” more which would correspond to the exhaust valve closing that same .0125” to .015”, (that would give you the .025-.030” OVERALL difference in valve height that is needed), but being as these camshafts are ground with asymmetrical lobe profiles, chances are it wont be exactly that, but it will be close. No matter if the intake valve “moves” more or less than the exhaust valve, the important point is that the sum of both indicators ends up totaling between .025” and .030”, which would be ideal in this scenario. Now lock down the adjustable cam sprocket, verify that the crankshaft did NOT turn during all this, double check that your intake to exhaust opening spread is where you want it and you are set.

 

 

 

Both intake and exhaust valves off their seats during valve overlap…

ValveliftMedium.jpg

 

 

 

 

 

Dial indicator on the retainer…

IndicatorLarge.jpg

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Hi Paul,

Thanks for this great info, as I am going to need it.

You mentioned setting the cam up say 0.25" and 0.30" advanced for the cam mentioned above, what would my Rebello cam advanced be?

 

Cheers,

Ian

 

Ian,

Since you purchased your Rebello cam elsewhere, I don’t know where it needs to be set. If you send me all the info you have on your cam, I would be more than happy to contact Dave Rebello and get that info for you.

 

Thank you for allowing me to use pics of your Cylinder head for pics in this thread.

 

Paul

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Paul,

My Rebello cam came direct from Rebello Racing. All the info I have is:

Quote " the cam specs are quite deceiving as the duration at 0.50 is about 226 deg, but the cam makes power like one of our bigger cams due to the unique lobe design. The lift is .487"

The only other thing is the cam is a 63D cam kit.

 

If you can find out the info, thats great.

Cheers

Ian

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Paul,

My Rebello cam came direct from Rebello Racing. All the info I have is:

Quote " the cam specs are quite deceiving as the duration at 0.50 is about 226 deg, but the cam makes power like one of our bigger cams due to the unique lobe design. The lift is .487"

The only other thing is the cam is a 63D cam kit.

 

If you can find out the info, thats great.

Cheers

Ian

 

Ian,

I talked with Dave Rebello today and he told me, with your cam and your large displacement L-series, (3.1) to set your cam up between .010” and .020” advanced. If you want more high RPM breathing he said he would lean towards less advance, i.e. .010” or even a little less depending on where you want your powerband.

 

 

Paul Ruschman

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So why do we degree in our cams? In hopes of getting the most out of our cams, right?

The exact cam timing specs as listed on the cam card or given by the cam grinder are really nothing more than a starting point. For most of the street crowd, they will set their cam to these specs and leave it, which is usually just fine for 90% of cars/drivers.

 

For those of you that are into fine tuning your power band to get as close as you possibly can to your intended goals with the car, just remember that there is NO “set” cam timing figures for any particular cam that works best on all L-series build ups. Your “ideal” cam timing specs will vary for reasons such as gear ratios, gear spreads, track conditions, driver comfort levels in street applications etc. For those of you that are anal about extracting every last bit out of your engines, those figures quoted on the cam card are merely a starting point, and depending on your induction and exhaust system, head work, type of track or street driving you intend to do, gear ratios and gear spreads, etc, you will no doubt be playing with advancing and/or retarding the cam from that starting point to shift the power band around up or down the rev range to maximize the power where you’ll be using it most. Just like finding that ideal ignition timing curve, ideal fuel map, ideal gear ratios, etc, playing with cam timing specs is another tool in the engine tuners tool box, used to “dial in” the engine for maximum performance for its intended purpose.

 

 

 

Good luck,

Paul Ruschman

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