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Discussion Starter · #1 · (Edited)
I figured this might help some folks out. There is a thread here somewhere on this, but it's not so straight forward and the pictures are missing. This process was done with the Comp Cams degreeing kit I got from Summit. Without further ado, I present to you a quick how-to on degreeing your GSC S1 camshafts...

This is assuming the motor is out of course, valve lash set to spec.

Have timing belt installed, set crankshaft and both cams to first cylinder TDC as per the repair manual. So cams with their arrows pointing at the indentations on the backing plate and the crank sprocket indentation pointing to the dot on your oil pump. You can leave the crank damper off for this. You will need some kind of space between the crank bolt and the crank sprocket. I used a huge aluminum washer/spacer. Try to centre the degree wheel as best you can since it has a large inner diameter and you want it to be concentric with the crank.

You can see here the piece of copper wire bolted on to the water pump where you normally bolt down the timing cover. Bend it with some pliers until it shows over the 0 degree TDC mark on your wheel. It gets set to mark the 0 degree for true top dead centre in a moment.





Now to find number 1 piston TRUE TDC, get a piston stop (I was impatient so I used a ratchet extension and it worked fine) and put it down spark plug number 1. A piston stop will ensure there's no wiggling but I found that with the piece I used, it was pretty obvious still where TDC was. Use the depth gauge on top of the piston stop. The big arm that comes in the kit threads perfectly into the small holes between the valve covers, over the spark plug holes. I used the one behind the first spark plug to give me room to work.

Rotate the crank clockwise until you hit TDC, note where this is on the degree wheel. Turn it some more, slowly until it's about to move away from this value on the depth gauge. Note this spot on the degree wheel. Go halfway between these two numbers on the degree wheel and you've got True TDC. I did this a few times just to make sure I was measuring correctly. Adjust your piece of wire or the degree wheel accordingly. It doesn't hurt to double check. I got lucky and was right dead on to start with.





Now set up your rig to place the depth gauge over the first bucket on the intake side at TDC. Have it compressed more than .040" because it will read negatively as the bucket moves away from the gauge. Some say it's hard but It's actually pretty easy. Use the inner front corner of the bucket so the cam lobe doesn't interfere and try to get the angle as close to the valve's path as possible. Make sure you have the cam rotated such that it is not yet acting on the bucket (flat part of the cam facing bucket), then set this point on the dial to zero.

*Note: In another thread, a member tried to use trigonometry (I think) to compensate for the angle of the dial not being perpendicular to the bucket. I asked Greg at GSC about this and he told me not to bother. In the grand scheme with thermal expansion, timing belt stretch, etc. the minute amount you would adjust for makes no difference. (Edit: Just make sure to have it straight on as possible to the lifter and check both your valve opening and closing events. The closer you are to having your measurement straight on, the closer your duration will be to 228. The worse your angle, the smaller the duration. If you have a dial with a longer needle available, this can help get a better angle.)

*Note 2: Some instructions make reference to setting the front bucket to zero lash. Do NOT bother on these cams. Kelford's site (who buys their blanks from the same foundry as GSC) addresses this point. We are just interested in finding when the valve is .040" open so the lash isn't really important, and we found TTDC without touching the valves, so no need for zero lash.



Turn the crank clockwise until the dial goes backwards to .060" (subtracting .040" from 0) and note where you are on the crank degree wheel.

*Note: Always turn the crank clockwise because that's where the tension is on the belt. If you wiggle "back and forth" you change the relation between crank and cams because you're loosening up on the tension and it won't just pull the cams back in sync.

This is just for reference, but mine was at 4 deg BTDC. The cam card specifies for 6 deg BTDC. So set the degree wheel to 6 deg ahead of TDC like here...



Now go up to your cam bolts, loosen them, put a socket and breaker bar (the longer it is, the more control you will have) and carefully move it (clockwise in my case to advance timing) until your dial hits .060" lift (or drop, if you want to get technical.) Here you can hopefully see that the dial is at .060" and the degree wheel reads 6 deg BTDC. Also, be sure to record your valve closing time. You should have a duration (amount of degrees between opening and closing) that matches your cam card. If not, the depth gauge is not on straight enough.



Blue loctite 242 your cam bolts and torque them down to spec. You're done here. Rotate it once or twice to make sure that when the dial hits .060" the crank degree wheel is hitting 6 degrees BTDC (which is 6 notches before the 0 TDC mark.) Disassemble your dial rig and move it over to the exhaust side.

From straight up, my intake was 4deg BTDC, exhaust was 45deg BBDC. The specs call for 6deg BTDC and 50deg BBDC, respectively so there was a change of 2deg on the intake side and 5deg on the exhaust side.

I'm not expecting huge gains here, but I paid good money for my cams and cam gears so I expect to get what the manufacturer intended for me to gain. This should (in theory) make my car run and idle optimally as the cam manufacturer intended. I'm not interested in a lopey idle setup that is sub-optimal. This was my first time doing this and I didn't find it that difficult. Hopefully, this helps someone else out and saves them the time I had to spend looking a bunch of stuff up. The Comp Cams kit worked perfectly. Greg at GSC is awesome for helping and responding to my emails about the cams/gears, etc. Here is a link to the youtube video by TwinsTurbo that really gave me a good visual.

http://www.youtube.com/watch?v=_MsqA-C3vGI

Enjoy!

-Eden.

Edit: Yay, 300th post!!!
 

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Discussion Starter · #2 · (Edited)
Additional Info:
So today I was rechecking things before I disassembled the rig since I hadn't checked the valve closing time. The exhaust side was bang on. Opened at 50deg BBDC, closed at 2deg BBDC. Then I checked my intake side and this is where my lesson comes in. It should open at 6deg BTDC, close at 42ABDC, giving a duration of 228 degrees. I can draw a wheel for people to see if it helps explain this. Anyway, mine opened today at 6BTDC but closed at 34ABDC, which opens correctly and closes 8 degrees too soon, shortening the duration to 222 degrees. However much you advance or retard the cam gear, the duration shouldn't change unless one of two things happened....

So I gave Greg at GSC a call and discussed it. He checked my grind code against his records and found that there is no reason why the cam itself should be giving me this error. After a lengthy discussion it slowly sank in for me. As the angle between the measuring gauge and the path of the lifter changes, the measurement you read and the true lift begin to differ. This made sense to me already and I figured it wouldn't matter because .040 I saw would be the same for the opening and closing of the valve... but this also means that the timing for opening and closing are being changed in a way that shortens the duration because you're getting this reading later than you should. (Since the hypothenuse is longer than perpendicular from the lifter.)

I got extra anal with my positioning of the dial and voila! It now opened at 7.5, closed at 39.5... Duration was back to 227 degrees (close enough.) So I centered my reading to open just a tad over 6degrees BTDC, and closing at about 41degrees ABDC. The remaining 1 degree of duration that's missing is very obviously a small remaining error in lining up the dial.

In hindsight, I take back my comment that it's "easy" to line the gauge up on the lifter. This also highlights the importance of measuring both opening and closing events. Or else if I had left it as it was, the timing would have been off by about 4 degrees (half of the missing duration since it was all the way over to the opening event, off by 8 for closing.) Hopefully this all makes sense. If not I can make a few pictures to illustrate the effect. Good luck for the few people who decide to take this on!
 

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Discussion Starter · #5 · (Edited)
I couldn't possibly tell you what gains I'll have since I will not be making adjustments on the dyno before vs after. The difference on the cam gear markings looks small compared to the adjustment on the crank pulley since they have a ratio of 2:1 degrees, so for the time it took to get these exactly to spec, I do not plan on setting them back and forth on the dyno. I'm so anal, that this took me a few hours to get exactly correct, give or take some measurement error, and that's with the engine out of the car on a stand, without the pressure of paying for dyno time :p I'll have some videos up later on showing the idle characteristics and whatnot, so you can compare with someone else who may have a video of the idle with cams installed straight up. Here's a pic of how small the adjustment looks on the cam gears themselves.

Intake (retarded 4 degrees)



Exhaust (advanced 5 degrees)

 

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Nice write-up .. Thanks for sharing
 

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Discussion Starter · #8 ·
Thanks guys, hopefully this will serve some people who wish to take on the endeavour. It's not overly difficult, but it can take some time to get it just right. I'm confident it will all have been worth it, considering the criteria and goals for my build. Besides, a little free horsepower (sorta) is always good :)
 

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Thanks guys, hopefully this will serve some people who wish to take on the endeavour. It's not overly difficult, but it can take some time to get it just right. I'm confident it will all have been worth it, considering the criteria and goals for my build. Besides, a little free horsepower (sorta) is always good :)
IMO, it should be a no-brainer to degree aftermarket cams, however, too many people prefer a lope over efficiency.
 

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Bookmarked and subscribed.
 

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Discussion Starter · #16 ·
My car is still at the fabricator. I was told "hopefully til..." basically yesterday. So, I'm expecting it back this week. Then I still need to break it in and then tune it. So the video should be coming soon :)
 

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great info, thanks! :bigthumb:
 

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Any updates?
 
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