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So, ready to bolt on the heads, just waiting for a couple extra shims to get me to .007" and .012" on intake and exhaust. So much easier to do this when the head is off!Disco, are you shooting for 0.007" & 0.012" dry during trial assembly? What sealant will you be using between the cam carrier and head. If it's an anaerobic sealant, like Loctite 518, then it's film thickness is 0.0005" (half a thousandth). In that case, dry-shim short by that half a thousandth to 0.0065" & 0.0115". Then the film thickness will 'float' that dry setting up to 0.007" & 0.012" during final assembly with the sealant applied.
discogodfather wrote:
(Snip)... I took 32 degrees, divided by two to get the cam degrees (it's my understanding all cam data is always in crank degrees) and then used a protractor to measure and rotate the cams into the correct position they should be AT TOP DEAD CENTER. Those are the WHITE marks.Here's a way to double check your work.
If you had stock pulleys installed with the timing marks aligned ON the centerline between the cams, and...
If you removed the nut & washer so you could see the ends of the camshafts in the pulley bores, then...
You would see that the keyways are located above that centerline between the cams.
The intake keyway is in the upper-left quadrant, at about 10:00 o'clock
The exhaust keyway is in the upper-right quadrant, and about 2:00 o'clock.
Each cam MOP has it's keyway a certain angular distance (degrees) above that centerline between the cams.
_97° MOP = 21.25° . . . . 97° is the Blue timing dot on a SINGLE-MOP pulley.
100° MOP = 19.75° . . . 100° is the Blue timing dot on a DUAL-MOP, Red-dot / Blue-dot pulley.
104° MOP = 17.75°
105° MOP = 17.25°
110° MOP = 14.75°
115° MOP = 12.25° above the centerline between the cams
The trick (and the Achilles Heel) will be in accurately locating the radial centerline of the keyway, and the centerline between the two cams, and accurately measuring the angle between them.
discogodfather wrote:
Question: Is there any data for the 104 cams at .050" or some kind of lift? It's hilarious that Dave Bean sent me a big write up on how to degree in cams that completely emphasizes the importance of degreeing at lifts and how it's much more accurate and better, but then no information about timing their cam!?First, not all 104 & 107 cams are created equal. Unfortunately.
Lotus designed the originals, and named them. Then, every Tom, Dick & Harry aftermarket cam grinder on the planet came out with their own 104 & 107 cams with different timing specs. That has created great confusion... why couldn't they have exercise a small shred of naming creativity for their own cams.
You're using Dave Bean BLL-104 cams, which are slightly different and call for 105 MOPs, so you should use Dave Bean's instructions... not Lotus' instructions.
Unfortunately, Dave Bean himself passed away a couple of years ago, and he was 'the' tech guy, 'the' engineer at DBE. And he didn't share much of the details about things he developed... including cams. The sales staff do not know the answers to your questions. I recently asked Ken Gray at DBE to contact their cam grinder, talk with an engineer, and get all the info about each of the cams they're getting from that company. He said he would. That doesn't help you for now.
I have old Dave Bean BLL specs from the mid-1990s... I can guarantee the BLL design hasn't been changed since then, but...
Lotus 104 = 32° / 60° / 60° / 32° -- 272° Duration -- 64° Overlap -- 104° MOP
BLL - 104 = 31° / 61° / 61° / 31° -- 272° Duration -- 62° Overlap -- 105° MOP
Lotus 107 = 22° / 50° / 50° / 22° -- 252° Duration -- 44° Overlap -- 104° MOP
BLL - 107 = 24° / 54° / 54° / 24° -- 258° Duration -- 48° Overlap -- 105° MOP
Lotus never quoted duration at any specific lift value, such as 0.050". Nor did they say duration was seat-to-seat, or not. Nor quote an angular position off of TDC at which 0.050" lift occured... either opening or closing. So, no direct answer to your question.
However, I knew an engineer at Lotus (retired), and he gave me the information on the two cam illustrations I posted above. He further stated that Lotus quoted duration between the tops of the opening and closing ramps. You won't find that in print from Lotus, but the info on the illustrations I posted is all per that engineer.
If you look at the two cam illustrations, keeping in mind that Lotus quotes cam duration between the tops of the opening and closing ramps, look at the ramp dimensions and you'll see that the 104 cam's opening & closing ramps are 0.010" high, and the 107s are 0.012" high. That's as close as you're going to get to a "measuring height" from Lotus, but it's not 0.050"... ADAPT.
In the 104 illust'n, the profile contour is 68° before, and 68° after MOP (ie, straight up centerline), or 136° total expressed in 'cam' degrees. But timing is expressed in crankshaft degrees, so 136° x 2 = 272°... which is the duration that Lotus quotes for the 104 cam.
If you start with your dial indicator zeroed on the base circle, rotate the cam until the dial indicator 'just' reads 0.012". Note the angular position on the degree wheel... you should have rotated 20° to that point. Rotate the cam, up over the hump and back down, until the dial indicator once again 'just' reads 0.012", and note the position on the degree wheel. You should now be at the top of the closing ramp.
The difference between the two degree wheel readings (from 0.012" before to 0.012" after) should equal 272° for a 104 cam... +/- manufacturing tolerances.
One half the difference between the two degree wheel readings is the half way point of your rotation, which is also be the lobe's Maximum Opening Point (MOP).
Regards,
Tim Engel
Last edited on 05-16-2020 07:47 am by Esprit2