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  #31 (permalink)  
Old 12-11-2006, 01:29 PM
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You can skimp on the intake clearance because the piston is running from the valve so the exhaust is one to watch because the piston is chasing the vavle.


.050 is okay with intakes, .100 with exhaust is better but .085 has worked. If you float the valves then......BANG.

With a 106 LCA installed straight up, you should have seen 106 on the degree wheel. You might need to check again. If 100 is what you verified, you would have a 6 degree's advance.

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  #32 (permalink)  
Old 12-11-2006, 08:25 PM
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Well this is the first time I have ever degreed in a cam, so I could have done it wrong. I have always just installed them straight up without checking anything, but they have all been mild cams also.

As far as the LSA, I can't tell you what it is on the cam, because I was never told. I was told to install it on the 106 and the 108 centerline, depending on which day of the week it was. The procedure I followed was:

Install cam straight up. I rotated cam to max lift on intake lobe of #1 cylinder. I zeroed the dial indicator. I rotated the crank clockwise until the lift dropped .050" on the dial indicator. I recorded the reading on the degree wheel, and then found max lift again. Re-zero'd dial indicator and went counterclockwise with the crank until I again was down .050 on the dial indicator. Recorded this reading on the degree wheel. I added the two recordings and divided by two. This is what I understand to be the centerline of the cam. If I recall, I came up with 100.25, which I rounded down to 100. I honestly don't recall which way I went on the crank gear, but I went 3 notches one way or the other. I re-did this procedure and got 106 the next time.

Did I screw this up, or was I on target here?
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Old 12-12-2006, 11:13 AM
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That doesn't sound right to me.

I find the max lift of the cam, then find TCD on the piston. If I'm installing straight up, I'll turn the crank to the centerline,101, 104. 106, 108, 110, 112, 114 or whatever. then install the belt, chain or gears. If I wanna go advanced, I subtract that amount from the LCA. 106 installed 4 degree's advance is 102. Install the belt, chain, gears, ect...

Just to verify it's right, find max cam lift by measuring a set amount, doesn't matter how you find it really, .050 is sometimes confusing with .050 tappet rise, I use .010 because it takes less time. Sometimes I just watch the needle till it starts going back down and back it up the crank a little bit. That doesn't really work as well with roller cams though because the nose is pretty flat giving a few degree's of dwell. It's less accurate. After finding the max lift, read the wheel. Should say what is on your card. Beware on custom race type grinds, the lobes are not always the same on both side. So the centerline is not spot on with max lift. Some grinds will lift the valve very fast and slow it down just before max lift, some will lift slowly and go past the centerline with lift then drop the valve suddenly while others will go fast and slow it down right before it hit's the seat. Some will launch the vavle off the nose. That's why it's best to measure at least .050 down both side of the lobe. .

It's fool proof to find TDC with a piston stop, then find the cam lobe centerline by measuring a set amount on both side of the lobe, divide by two, then divide by two again. That no. should be what's on your card.

I hate that cam companys tell you they have ground the cam with advance "Built In". It get's confusing when you want to install 4 degree's but the cam company has already done that and you need to install straight up. I hate when someone else compensates for me. You end up compensating for their compensating. Why don't they just tell you what the real centerline is ans let you figure it out?
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Old 12-12-2006, 04:43 PM
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The way I read it, the two methods achieve the same thing. Instead of relying on the cam manufacture's indicated centerline, with my method I found the centerline myself (I think), by finding the point where max lift is. With a roller cam, max lift can be for 10 crank degrees (for round numbers). The centerline should be the center of where max lift is achieved. By letting the lifter drop .050 in each direction, you can find that perfect centerline IF the lobe is symmetrical. If it's not then that whole theory gets thrown out of the window, and goes along with what you were saying about setting the valve down slowly or opening it quickly.

When you install the cam straight up (only one way I know to do this), you align the dots on the timing chain and the pin in the camshaft. I assumed that you install it this way and find the max lift on the intake valve (using the method above), and that is your centerline. If that isn't the case, then I'm not quite up to speed on this.
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Old 12-13-2006, 01:43 PM
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Let's omit the gears and chain. If the Cam card says the cam opens the intake at valve 106 degrees BTDC, Then you put the crank at 106 BTDC and set the cam so the lifter is sitting on the center line. That's it. That's called straight up. If you advance the cam in the cycle, you will be opeing the valve sooner BTDC. That lowers the 106 to 10whatever you advanced.

My point? that get's confusing with where to measure. Wanna be safe? use .150 or .200 thousands to on either side. It's just more accurate. More accurate than most wheels I bet.

What ever method, you need to verify TDC by finding either side a predetermined amount on both the cam and tappet.

By installing it the set up first, you are checking the chain and gears for proper machining too. Which is off quite a bit on cheap ones. Another reason why belt's are better. More adjustabilty by turning a screw than by moving teeth.
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Old 12-13-2006, 04:57 PM
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I think I see what your saying. The first problem is I DIDN'T GET A CAM CARD!!!

I don't know of any cam manufacturer that does not supply this. I thought this was a standard practice. I was told after receiving my cam that the cam card computer printer was down and they would mail me one as soon as it came up. When I talked to Chet, he told me they didn't do cam cards! Not that has anything to do with what Johnsongrass1 was saying, but I thought I would bring that up.

Not sure if Jay Allen floats around on here or not, but after some posts on another forum, I decided to give him a shot. First of all, from my ~45 minute phone conversation with him last night, he's a super guy and if I get the kind of customer service from him during and after doing business with him, I'm hooked.

The time we talked was just going over what I had and what different cams would do for me. This is more time than I have spent on the phone with Chet Herbert, or any cam company talking with someone about my particular application. I can't vouch for his products (yet) but from the estimates he gave me I think I will be more than happy.

As far as degreeing the cam goes, If I understand what you are saying, our process is basically the same, it's just our wording that seems different. Even with the cam installed "straight up", I had valve clearance issues, so regardless of whether I degreed the cam correctly or not it still wouldn't have worked with my setup. I'll keep you guys updated on the progress...

Travis
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  #37 (permalink)  
Old 12-14-2006, 12:28 PM
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That's why he said retarding the cam iwll help resolve those clearance issues. Retarding the can a 4 degree's will raise the overall power curve about 3 hundred rpm. Not anywhere enough to matter on a street motor. Even without a cam card he should be able to tell you over the phone what those specs are. Unless it's custom grind. Then some keep the files and others don't.


Quote:
Originally Posted by TravisT
I think I see what your saying. The first problem is I DIDN'T GET A CAM CARD!!!

I don't know of any cam manufacturer that does not supply this. I thought this was a standard practice. I was told after receiving my cam that the cam card computer printer was down and they would mail me one as soon as it came up. When I talked to Chet, he told me they didn't do cam cards! Not that has anything to do with what Johnsongrass1 was saying, but I thought I would bring that up.

Not sure if Jay Allen floats around on here or not, but after some posts on another forum, I decided to give him a shot. First of all, from my ~45 minute phone conversation with him last night, he's a super guy and if I get the kind of customer service from him during and after doing business with him, I'm hooked.

The time we talked was just going over what I had and what different cams would do for me. This is more time than I have spent on the phone with Chet Herbert, or any cam company talking with someone about my particular application. I can't vouch for his products (yet) but from the estimates he gave me I think I will be more than happy.

As far as degreeing the cam goes, If I understand what you are saying, our process is basically the same, it's just our wording that seems different. Even with the cam installed "straight up", I had valve clearance issues, so regardless of whether I degreed the cam correctly or not it still wouldn't have worked with my setup. I'll keep you guys updated on the progress...

Travis
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