disclamer: I am not responsible for anything YOU DO TO YOUR OWN ENGINE. This a 'do at your own risk' thing... This is for informational purposes only. Don't fuck around with things your don't understand, unless you are willing to pay for your mistakes. I learned the method to do this on an over-head-valve engine, not a OHC engine... where you have rocker arms.. in the 7M there are no rocker arms or push rods, etc... so this method I 'pulled from my own ass'... as a best I could figure out given the circumstances.
After machining the block and head, and changing the headgasket thickness on an over-head-cam engine like the 7M-GTE, you cange the distance between the cam gears and the crank timing gear. If the change is minimal, you will get a very minimal change in timing, but when the change is large, you can have valve timing off by a very significant amount.
To properly degree your 7M engine you will need: Degree wheel (11" or smaller), 3 20mm washers (to space the wheel), scrap coat hanger (for wheel pointer), wrenches, dial gauge (1" travel and 0.001" accuracy is good enough), dial gauge fixture, scrap piece of metal to mount the dial gauge fixture, notebook/pen, and a pair of adjustable cam gears (you NEED 2).
The dial gauge/fixture I got from harbor freight.. the dial gauge from jegs.. and for cam gears I am using AEM.
In my case 0.005" was machined off the block deck to clean it up, I changed from the stock 1mm gasket to a 3mm gasket (to drop the CR), and I had an unknown amount of material machined from the head (rebuild head, no specs were supplied :). You can calculate the timing change if you know the actual change of distance between the head and the block, and get a number that is spot on... But since I don't know how much the head was machined I decided to 'degree-out' the cams and figure it out for sure. Degreeing the cams also gives you the benefit of validating the timing marks on the engine, which are not always very accurate.
The 7M is not the easiest engine to degree. Mounting a degree wheel on the crank is somewhat cumbersome because the crank bolt is recessed inside the balancer pulley. Also, replacing the crank bolt with a longer one that would allow for mounting the wheel was impractical since the crank bolt is a 18mm thread, which is not readily available (common sizes are 16mm then 20mm, 18mm is rather uncommon... at least in the US). So I simply removed the crank bolt, and the balancer pulley, leaving the timing gear in place (it is held in place with a woodruf key). Then you can install the degree wheel (with a spacer washer) using the crank bolt (without balancer) right on the end of the crank... this provided a nice flush surface and I was able to clear an 11" degree wheel quite nicely.
I modified a spark plug to use as a piston-stop, found TDC, using a pointer made from a coat hanger... Note that since the balancer is off you cannot very easily correct the factory TDC marks very easily (at least not at this point). If you don't know how or don't want to make your own piston stop, you can readily buy them from somewhere like Jegs... just make sure to get the right threading, etc.
Okay, now we have a degree wheel mounted and TDC has been located accurately. Now we have a reference point for figuring out the cams. This is where it gets really tricky. On reground/aftermarket cams you get a card that tells you all the info you need, and makes your life really easy... but I am using the stock cams, of which there is very little information. On top of this, mounting a dial gauge on the lifter is nearly impossible due to the design of the cam/lifter... so I came up with my own method that worked out fairly well, but took quite a bit of extra effort.
The first step was to get a degree-vs-lift profile of the cam lobe. Mount a plate between the two cam-cover holes that sit on either side of the spark-plug galley right next to the first lobes of the cam-shafts. Use this plate to mount an adjustable dial gauge fixture. Rotate the crank so that the top of the lobe is pointed straight down (vertically, so it is pushing down the lifter)... the top (exposed part) of the cam lobe should be at its minimal point.. setup the dial gauge so it is touching the exposed part of the lobe. Make sure that the dial gauge is perfectly perpindicular to the lobe both side to side, and front to back, and that is it solidly mounted. Zero the dial. Now turn the crank to TDC. From here, record the dial gauge reading, turn the crank 10 deg. and repeat. Remeber: you must turn the crank in the same direction that it operates, otherwise you will slacken the timing belt slightly and get bad numbers. Do this for all 720 deg... and you will get a nice profile of the cam... plot it in something like gnuplot or ms excel. Before you move that fixture, look at what your max lift was.. I have something close to 0.295".. Now subtract 0.010" from that, and rotate the cam (clockwise!!) until you reach that lift (0.285") on the rising side, and record the angle. Continue rotating until it goes past max lift, and hits 0.285" again, record that angle.. this is for later. Now move the fixture over for the exhaust cam, and repeat.
Okay, now you know what the profiles look like, but all the numbers you have are crap because the angles you took are shifted an unknown amount. The angles you wrote down are relative to themselfs, but you didn't measure them from the lifter, rather from some unknown location on the other side of the cam. This means that you don't know what the profile degrees mean in relation to the actual cam/crank degrees... So now for more measurements to figure out how to 'clock' or shift your numbers so that they match up with what the lifter is doing... pain in the ass, right? It's not too bad from here. What you need to do is rotate the crank (clockwise... remember!) so that the #1 intake lobe is pushing down ALL the way on the lifter... this gives you engough room to setup the dial gauge so it touched the lifter. Note: you will have to really angle it in there, probably around 45 deg, so that the end of the dial gauge is sitting nicely on the face of the lifter, and that the shaft is not touching the cam lobe (MAKE SURE it doesn't touch, it will mess up all your hard work). This setup will not give you accurate lift measurments since the geometry is not square, but thats okay. Now zero it out again, and rotate the crank counter clockwise until it reads about .015" from maximum lift (remember you zero'ed the gauge at MAX lift, so we are looking for 0.015" from max lift!!).. Now rotate clockwise untill you reach 0.010" from max lift. Record the crank angle. Rotate thru max lift until you get the the other side and it reads 0.010" again. Record the angle.. if you have to back it up, do it ALL over because of the slack you created! Do the same for the exhaust side.
What did you just do? Well, the stock cams are symmetric (look at a graph of the profile you made).. this is true of almost all stock cams, and it makes our lives that much easier. The midpoint between your two angle measurements is the point at which your cam lobe is at maximum lift.. this is your reference point! Now take the same angles from when you did your profiling. The difference between the profile data's max lift point and the max lift point on the lifter will tell you how much to shift your profile data to make them match up... remember the max lift degree on the lifter is the REAL value.. so shift your profile data so the profiles max lift point matches the lifter!
Plot your data.. Make it easy and plot it over 720 deg so you have the intake and exhaust profiles on the same graph. Time for a sanity check. Make sure that the two profiles are symmetric, and that they overlap. I graphed mine so that they overlap at 360 deg (the center of the graph) so that they sit nicely in the center of the graph. They need to overlap. The exhaust valve should be opening first, then intake, then at either end of the graph they should be closed (see my graph below)... if any of this is wrong.. GO BACK AND CHECK: Make sure that your really got the timing as close as possible, you may be of a tooth. (adj. cams usually only go 10 CAM degrees or 20 crank degrees either way, so there is only so much slack for error). You also need to make sure that the gears are relatively in the right position... that is: the distance between the two cam gears DIDN'T change.. so they should be relatively in the right position.. so if they don't overlap like in my graph, they are not setup right! Go back, fix your problems, and then do whatever part you need to again untill your data looks correct. If you look below I am off by 6 crank degrees (3 cam degrees), and that is after adding roughly 2mm of height to the head, so if you are off by much more than that, you should think about checking your numbers again.
I am assuming that stock cam position has the cams symmetrically timed about TDC... so the intersection of the profiles on the graph should occur exactly at 360 deg. This seems like it is approximately what I expected from a guestimate using the change block height (only a guess, as I don't know how much was machined off the head). So the difference of the angle at which the profiles intersect and 360 deg is how far off your cams are from 'stock'. There is not enough information from the factory to really 'know' what the phasing of the cams should be, but this is a pretty good guestimate.
Here is my data: The first set 'int.dat' and 'exh.dat' is the actuall position of the cams. They are off by 6 crank degrees due to machining. That means to get them back in the stock position they need to be moved 6 degrees. The second set of data int2 and exh2 are after shifting it back 6 degrees, and then for performance resons, I have the exhaust cam advanced 3 crank deg, and the intake retarded 3 crank deg (from stock). I have also plotted the vertical position of the crank journal (labeled crank... not to scale) and marked TDC and BDC timing points to make everything clear. The profiles are a little jagged, this is because the data was only taken at 10 deg increments... if you would like a smoother graph, just get s'more data points :) for what we are doing here, it doesn't really matter since your finding the real peak accuratly anyways.
Now. change your adj cam gears so they are where you want them! This should be easy with your new-found knowledge. But note that when you move the exhaust cam you are changing your ignition timing!!! The CPS or distributor is geared off of the exhaust side cam... so after you set your cam timing, and get it started up again, reset your ignition timing... in my case it was about 6 degrees off!
Remember: this will get you about where you want, but to fine tune you really need to put the thing on a dyno. Esp. if you are trying to tune for a certain powerband, etc. Like I said, this is a really good starting point, and even with a dyno, it will give you a better picture of where you're at.
Okay, so its all done. So we need to get the crank pulley back on. What you want to do is set it to TDC, and then mark your timing belt with a nice THIN line, and bend your timing marker (coat hanger) to point at it... This way when you inadvertenty move the crank while taking off the wheel and remounting the crank pulley, you can then return the crank to what you marked as TDC, and check the timing mark on the pulley with the real TDC... if you figure out a way to mount the degree wheel without removing the pulley, more power to you, because this step is a lot easier... note: you need the correct mark on the crank pulley because you need to set your ignition timing!!! why spend all that time getting your cam timing correct when your ignition timing is off?
If the terminology I'm using doesn't make sense to you, or the process is a complete mystery, don't do it... Please only use these instructions as a guide, not as the gospel. If you mess up your engine, even following my instructions, too bad, it's not my fault, it's yours :)
good luck... what a pain in the ass :) if this didn't make sense (because you understand it, and it doesn't make sense), or if you have any better ideas as how to do this, or you think I did something horribly wrong, please shoot me an email.. I wrote this page since nobody on the internet seemed to know how to do this... so I (carefully) pulled this method out of my ass... so I would be happy to update this with better/more useful/more accurate info and methods. thanks!