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| Mapping accurate cam events with dial gauge/degree wheel https://slantsix.org/forum/viewtopic.php?t=44921 |
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| Author: | MattyBrown [ Tue May 10, 2011 5:10 pm ] |
| Post subject: | Mapping accurate cam events with dial gauge/degree wheel |
I have been educating myself extensively on the art of degreeing a cam. I am fully aware of how to determine TDC with a piston stop and figure out my cam's intake lobe centerline. Should be no problem at all. The only task in front of me that I am a little hazy on is how to accurately map out the events of the intake and exhaust valves opening and closing. I want to pinpoint the exact moment (degree) that each of these things happen. When I'm determining the intake centerline, the book that came with my kit recommends I take the gauge reading from the valve retainer and set the lash to ZERO. But what about when I'm checking for the valves opening and closing? I have read some things about a slight ramp on the cam before these events and/or something about .006 lift? Would it make sense for me to set my lash at .006 before attempting to map the degree of these events? I just want to make sure that the specs I come up with are as accurate as possible because they are going to be my only reference for (possibly) IDing the cam and determining where to set valve lash. By the way, I'm going to be thoroughly embarrassed if I end up having a stock cam!!! But I really don't think that I do. My experiences with trying to get this car to run right are strikingly similar to what I've read about on Wjajr's "mystery cam" thread. As always, thank you very much for all info. I'm learning so much amazing stuff on this site!! -Matt |
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| Author: | WagonsRcool [ Tue May 10, 2011 7:21 pm ] |
| Post subject: | |
AFAIK, most cam manufacturers take mechanical lash ramps into consideration. So any specs at .050" lift are from zero lash. |
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| Author: | MattyBrown [ Tue May 10, 2011 9:51 pm ] |
| Post subject: | |
So, let me just make sure I get this... You are saying that whatever degree I am on when I reach .050 on either side of the lobe centerline will be my OPEN or CLOSE spec? If I am at the highest point for the intake, and I turn the wheel clockwise until my dial indicator gauge reaches the .050 point, that degree should match the VALVE CLOSES spec for my cam? Sorry I know I pretty much just said the same thing twice, I just really want to make sure I have full understanding of this and don't goof it up on Thursday. I'm getting sick of pulling out my radiator! I want these tests to have conclusive data! THANKS! -Matt |
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| Author: | wjajr [ Wed May 11, 2011 6:29 am ] |
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Matty, I know what you are going through. I went to the same party last January. All I can say is this will all sink in sooner or latter, and if there was an experienced degree wheel operator that could be standing next to you while rolling engine over, this learning curve would take about three minutes. LOL Hopefully it won’t take you four pages of dialog to get up to speed like me. Bill |
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| Author: | MattyBrown [ Wed May 11, 2011 7:29 am ] |
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Hey Bill. Yeah, I've read through that thread quite a bit now. It's definitely helped me to get an idea of how to approach this. Sounds like a very frustrating time for you though! How's the engine doing now? Do you have it running good? I think I have learned my answer from your thread after reading through it again. It seems to me, right now, that I need to make note of Valve Open/Close when I am at .050 APPROACHING lobe centerline (as opposed to moving away from lobe centerline). This would mean, to find Intake Opens, I would turn crank clockwise until first instance of .050 on the dial. Take degree reading. Continue clockwise past lobe centerline, past .050 on the dial and then turn counterclockwise until I reach .050 and mark that degree as Intake Closes. Can anyone confirm that this is correct? -Matt |
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| Author: | CNC-Dude [ Wed May 11, 2011 10:29 pm ] |
| Post subject: | |
Also, keep in mind that when checking the dimensions at the valve, the cam card specs are likely to vary somewhat from what you are actually reading on your indicator or degree wheel, compared to reading them at the cam lobe. The manufacturer is assuming a true rocker ratio when giving the specs at the valve. Using a stamped rocker, you will notice some variation in your readings that don't match exactly to the cam card. |
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