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Post by crazypj22 on Apr 29, 2006 10:34:00 GMT -5
Finally got time to set up and degree cam on skimmed head. Not as much difference as I originally thought there would be. I also found the numbers I got when I took motor apart but there is a 2 degree variation so I'm not sure if I have the same cam (got several motors stripped down) My original numbers were Intake open, 16Deg BTDC@0.040" Intake close 42deg ABDC which gives total of 238degrees. The measurments I took this morning are Intake open 8 degrees BTDC Intake close 48 degrees ABDC which only gives 236 degrees. Maybe my first measurements were off or maybe there is a slight production variation? Both tests were done at zero clearance, checked at TDCC. I like to set up DTI with 0.040" at TDCC so I can just look for zero position at 0.040" Heres a couple of pics anyway, First one is DTI at TDCC, there is slight parralax error in picture but it was dead online when viewed straight on. (pic wouldnt work as tthere was too much reflection) Second pic is amount before TDC with 0.040" showing on Dial test indicator. Third is the degree wheel and fourth the degree wheel as valve closes. There is slight run-out in cam base circle but its less than 0.0005", at normal valve clearance it wont have any effect img156.imageshack.us/my.php?image=dtitdcc1cr.jpgimg156.imageshack.us/my.php?image=8degbtdc7zl.jpgimg156.imageshack.us/my.php?image=dti8degbtdc3ih.jpgimg156.imageshack.us/my.php?image=degabdc1re.jpgI will be pressing chain wheel off cam and re-fitting in a better position I hav'nt done the exhaust side yet, probably not a lot of point as it isnt adjustable (but I will need the numbers to design exhaust system) Let me know what you think. PJ |
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Post by grizld1 on May 19, 2006 22:55:08 GMT -5
One part of this business we haven't covered yet--you know how many degrees you're off--now how far do ya move the sprocket?
In the case of my Shell regrind, after getting on the nearest tooth to spec. I wound up 4 degrees retarded. 4 degrees of crank rotation=2 degrees of camshaft rotation, so the sprocket needs to be moved 2 degrees back (forward being direction of engine rotation), or clockwise as viewed from the left.
So how far is that, at what point on the assembly? One way to figure it is to measure the large round boss on the left (alternator) side of the camshaft--the round part with the timing groove in it against which the sprocket is pressed. On my cam, mean diameter of the boss was 2.095". Multiplying by Pi (3.1416) gave a circumference of 6.582". Dividing that by 180 (2/360) gave an arc segment of .0365"--just a tad under 1 mm.(.927)--as measured at the outer edge of the camshaft boss.
pj--is it possible the first measurements you took were with an early (pre-1980) 447 cam and the later ones with a later (80 or after) cam? That'd account for the 2 degree difference in duration (1 degree either side of TDC).
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Post by srinath on Jan 6, 2010 15:45:11 GMT -5
Oh I have a related question.
I have to turn my right side cam 41.5 degrees.
Can I cut open a cam shaft and weld on a 2 or 3 bolt flange and bolt it on either on the cast part inside the sproket or on the sproket itself and get it aligned etc
Cool.
Srinath.
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Post by srinath on Jan 7, 2010 21:20:04 GMT -5
OK similar idea to mine.
The welding idea back fires cos the ends have to be in under 2 thou run out.
The rotate and bolt on takes care of that by being washer adjustable. If its a wee bit to the left, take off the right side washers and sand em a wee bit.
3 legged stool finds its own level, so a 3 bolt flange can be aligned to your head ...
BTW I have 3 cam shafts ... plenty to waste no problem.
Also I am going to run electronic ignition triggered form the crank - like a banshee rotor mod on steroids.
Banshee rotor or even an ex500 rotor, EX500 stator, ex 500 trigger coils and ex 500 ignitor box wiht a pair of EX500 coils firing the mixture. I can plug the cam or not bother drilling it and just using a knurled slug to align it inside ...
Cool.
Srinath.
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Post by beekay on Jan 9, 2010 8:30:27 GMT -5
If you set up everything then bore it, at least then your bored hole will be concentric with the bearing fit area. Then when you rotate it, it will still be true.
There's nothing that promises you that the hole down the center of your cam is concentric with the other machined areas, as it came from the factory. I'd re-bore it
I'd like to find out how yours works though... and how long it lasts.
I'm gonna make one like that and weld it.
Actually, attaching a flange on there like you're thinking isn't a bad idea.
Bolt it together to position it... Then weld it
Between the flange, and the sleeve down the center, then the welds, it would stay together. And be correctly timed and aligned as well.
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Post by grizld1 on Jan 9, 2010 8:42:44 GMT -5
Gentlemen, you are way OT on a thread stickied for reference purposes. Take this elsewhere.
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Post by mrriggs on Sept 12, 2010 2:10:42 GMT -5
I just installed an early model cam into my late model motor which requires swapping sprockets and degreeing it. I used a little different method then what has been mentioned already.
A press was used to remove the sprocket but instead of pressing the new sproket back on, it was heated with a propane torch and dropped into place. You have a couple seconds after it's on that you can turn it to line up scribe marks.
Instead of using the opening and closing events to time the cam I looked at the lobe centers. The advantage of using lobe centers is that it doesn't vary with changes in valve lash. A new cam will list the lobe centers on the cam card. Since all I had were the opening and closing events for my cam, the centers had to be calculated.
The intake opens at 47° BTDC and closes at 67° ABDC so the duration is 294°. Divide that by 2 and subtract 47, the centerline is 100°. The exhaust events are 60° BBDC and 41° ATDC. That makes the centerline 99.5° {((60+41+180)/2)-41}.
With the degree wheel setup, roll the motor over until the valve is fully open. Mount the dial indicator and bring it down to the retainer with a little preload. Turn the motor back and forth to find max lift. At this point zero the dial. Pick a reference point, I use 0.010". Roll the motor backwards until you go past the reference point on the dial then turn it slowly forward. When you reach the reference point, stop and read the degree wheel. Continue turning the motor forward past max lift and stop again at your reference point on the way down. Read the degree wheel again. Add that number to the number you got on the way up and divide by two. That is your lobe center. If your intake lobe center is greater than the spec then the cam is retarded.
My intake center was about 103° the first time. I used a method similar to what grizld1 posted to find out how much to move the sprocket. Carefully measured and scribed a new line. Pressed the sprocket off, heated it up, dropped it on, lined it up to the new mark and waited for it to cool down. When I put it back together the intake center was 99.75°. That's close enough for me.
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Post by mrriggs on Jun 23, 2011 13:37:36 GMT -5
As a follow-up to what I posted before. That method of measuring lobe centers only works if the cam lobes are symmetrical.
Last night I degreed a Shell #1 cam. The lobe centers based on opening and closing events were dead on 100°. But when I measured them at 0.010" below max lift they were 93° In / 97.5° Ex. The same at 0.020" to 0.040". At 0.050" they were 94° In / 98.5° Ex. At 0.100" they were 96° In / 99° Ex. Clearly, these lobes are not symmetrical.
Calculating lobe centers from the open and closing events was far more accurate. You don't even need to know what the opening and closing events are, which is good since this cam did not come with a spec card. Simply pick a point like 0.050" from seat and find it on both the up and down noting the degree reading. From this you can calculate the duration and lobe center. The duration number will change based on what number you picked or how much lash you have on the valves, but the lobe center will be consistent.
I measured this cam at 0.010" intervals from 0.010" to 0.070" and all lobe center calculations from 0.020" to 0.070" were within a fraction of a degree from 100°. The lobe center specs at 0.010" were off by as much as 6° and were all over the chart. This is because I was using zero lash for all measurements so it was picking up the "quiet ramps" that are normally used for gently closing the lash gap.
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Post by grizld1 on Jun 24, 2011 13:54:24 GMT -5
Yep, that's what to do. Inspection lift on Shell camshafts is .050" with valve lash set to zero, and that's where you'd read your valve events if you have the spec card. You did a great job of thinking through the operation without it! The original #1 grind specs were IO 25* BT, IC45* AB, EO 45* BB, EC 25* AT at .050" lift and 0 lash, but rumor has it that Shell experimented with some variations late in the game. Shell's spec for operating lash is .006" I, .012" E.
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Post by mrriggs on Jun 25, 2011 1:49:16 GMT -5
The original #1 grind specs were IO 25* BT, IC45* AB, EO 45* BB, EC 25* AT at .050" lift and 0 lash, Funny, those are the exact numbers I got at 0.050" with zero lash. They must have switched back at some point. |
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Post by grizld1 on Jun 25, 2011 10:03:40 GMT -5
Let me lay some stress on that word "rumor!" I don't know if Shell ever altered the #1 specs--that tale was told by Dick Fox after he'd taken over Shell Racing and some of the "#1" cams he sent out didn't measure to spec. Sounds like you got a good one--congrats!
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