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| So I was thinking about cam timing and... | |
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| Tweet Topic Started: Aug 17 2012, 10:14 PM (1,503 Views) | |
| metro_neel | Aug 17 2012, 10:14 PM Post #1 |
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was wondering if anyone else has ever thought about this....I have the "95" cam gear with the "60A" and the "80C" timing marks and alignment groves and I had to look up which was stock and which one was 2 degree advance because I couldn't remember (those who haven't heard of this, the 80C mark is "stock" and the 60A mark is 2 degree advance according to my research) and I got to thinking....You know how when you put timing gears on any motor like the metro design, you have a little bit of "play" or "rock" back and forth on the timing gears before you torque the bolt down because of the very small about of slack in the crankshaft key, crankshaft key way, crank gear key way, and up top between the cam gear and its alignment pin? Well (not that I think it would make really any difference at all) I was wondering if you held the crank gear clockwise with steady pressure as you tightened the bolt down and held the cam gear counter-clockwise with steady pressure as you tightened the bolt down you would probably gain just a little tiny bit of more valve train advance....even though it is a very small amount, I could see it "adding" up to at least 1 degree of advance(as opposed to them being "held" the opposite way). Like I said, its such a small about it may not even be able to be measured with a degree wheel....but on the other hand, if I remember correct, if you are one tooth off, it makes your timing like 18 degrees off.....when you think about that little bit of movement between the two gears added together, I could see that "distance" easily being at least 1/18th of a tooth....which would amount to 1 degree advance at least....anyone else ever ponder this? Or am I just crazy or have I just lost everyone?
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| clarkdw | Aug 17 2012, 11:28 PM Post #2 |
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It will affect cam timing. The difference would be easily measurable on a 16" degree wheel like I use. The difference would probably not be measurable in terms of "seat of the pants" changes in performance or fuel economy. There are just too many other variables. Which way do you want to take out the slack? One way could maybe net you slightly better mileage or power at 3200rpm and the other direction at 4000rpm. It would require a huge amount of research to figure out which would be best for an individual application. For changes that small an infinitely adjustable cam sprocket is the answer. I modified a stock one for adjustability or you can purchase one and the payback period in fuel savings would be in years for such a small adjustment. |
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| metro_neel | Aug 18 2012, 08:12 PM Post #3 |
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Well being that 3tech sells the modified 10 degree advance sprocket, and I have one stock single position sprocket and one '95 two position sprocket, I might as well use the 2 degree advance position and "adjust" the pulleys to have as much advance as possible.....which i highly doubt would end up being over 3 degrees....am I correct in my thinking that if I hold the crank sprocket to the right and the cam sprocket to the left, I would be "advancing"? being that when the crank sprocket reaches its timing mark, it is just a tiny bit "ahead" of the crank and when the cam sprocket reaches its timing mark, it is actually a little late and the cam is just a hair ahead of the sprocket? just wanted to make sure I was thinking about this right lol it was late last night when I was pondering this... |
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| Coche Blanco | Aug 18 2012, 08:39 PM Post #4 |
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Troll Certified
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Yes, but there isn't that much "slop" in the hole....and yes, that's what she said. |
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| HelterSkelter | Aug 18 2012, 09:17 PM Post #5 |
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#1 Pizza Driver
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you might be able to dremel out a little bit to advance it a little more. i'd be sure to put something to block the alignment peg from moving around though. |
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| clarkdw | Aug 18 2012, 10:38 PM Post #6 |
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If you plan on using the 95 sprocket on your 97 it won't work with the 97 timing belt. The 97 belt is wider and will overhang the earlier sprocket.
Assuming the dowel is centered about 7/16" (just a guess on the measurement) off the center of the cam a movement of about 0.004" of the dowel will change the timing one degree. Can you control your filing of the hole down to that precision? Just a lot easier to get a modified sprocket from 3Tech and know that it has been set correctly. He did all the research and knows where the cam belongs for almost any engine combination. |
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| metro_neel | Aug 18 2012, 11:15 PM Post #7 |
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i guess i have a 95 style timing set then.....because after you mentioned about it being too narrow, I went out and looked at the 97 sprocket is actually wider than everything else I have and the new timing belt I got fits the 95 one perfectly even though I am 99.99% sure I looked up a 97 when i bought it.....but the crank sprocket has the reluctor ring for the crank sensor...so im not sure how that could be a 95 setup but everything matches up right when i use the 95 cam gear so idk what i have going on here....I have two motors, one is a 97 and the other one i bought was all mix matched....had the two position cam sprocket on it, crank gear with reluctor wheel but the non-crank sensor oil pump and non-crank sensor oil pan....because at first i was pissed when i bought this other motor to use (the 97 block is most likely not rebuildable) because I had not realized at the time that the crank sensor went through the oil pump making the blocks interchangeable as long as you put the oil pump and oil pan from the newer design on.....and in case anyone was wondering......reluctor ring + pre-crank sensor oil pump = reluctor ring cutting little notches out of the oil pump housing.....lol And im not looking to file the notch at all or anything like that, thats kinda opening up a whole new can of worms if you don't have a degree wheel and the know how on using it properly....plus for the cost of a 3tech gear, its not even worth the bother....I was just looking at the best way for me to install what I have. lol |
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| metro_neel | Aug 18 2012, 11:21 PM Post #8 |
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just for reference, ill add some pics....![]() ![]() ![]() ![]() |
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| j63812f | Sep 9 2012, 12:43 PM Post #9 |
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J R
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Ive seen this stated in here now that the 80 is the 2 degree advance and that the 60 is the 2 degreee advance as well. Does anyone in here know for sure which is which? |
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| clarkdw | Sep 9 2012, 01:04 PM Post #10 |
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Look at the grooves that you use to set the cam timing. Of the two one will be 2 degrees further anti-clockwise when you compare it to the profile of the teeth. It is visible. The one that is further anti-clockwise is 2 degrees advanced. Mine is not accessible right now or I would check but I know that one of the grooves is right on the edge of a tooth and one is fully on the tooth. The one that is fully on the tooth moves the cam 2 degrees clockwise (advance). |
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| j63812f | Sep 9 2012, 02:17 PM Post #11 |
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J R
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I think I have it, 3tech stated it in a thread last year that 80 is 0 and 60 is 2 degs, so the easy way to remember is 80C = Center(0) and 60A = Advanced. Not sure why they put the numbers the way they did. Hope this helps the masses that are still scratching their heads. |
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| j63812f | Sep 12 2012, 11:15 AM Post #12 |
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Really like the red head on the clean block, looks awesome. what is all the electrical tape on the filter for??? Edited by j63812f, Sep 12 2012, 11:15 AM.
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| rjsdotorg | Sep 12 2012, 05:37 PM Post #13 |
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R E Member
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That's exactly what I did: note the ADV reminder mark. I used a round file and calipers and removed ~.030 from the side to allow the shaft to rotate CW, then I tacked a little tin solder to the other side and filed that so the cam pin just fits. 2-3 minutes total. I calculate that to be ~7.7 degrees. |
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