| Author | Message | ||
| Ric Rainbolt (Ricrain)
New member Username: Ricrain Post Number: 42 Registered: 2-2002 |
That makes sense with the 0.5mm shim. I guess I'm used to doing it the "slow" way.  | ||
| Charles I Claussen (Atlantaman)
New member Username: Atlantaman Post Number: 6 Registered: 3-2002 |
Ric--thanks for the info. I did some calling today and discovered that indeed there is a .5mm shim available. Now the way you discribe gives the same result, but the proceedure I got from 2 service guys today was the following. After setting all your shims, remove the #1 intake and install the .5mm shim. place a finger on the shim and move it back and forth while rotating the crank. when the cam lobe touches the shim it will stop moving under your finger--that is the spot.... the .5mm shim allows the cam to rotate so that only the tip of the lobe engages--this way the contact will be sudden and easy to distinguish rather than a gradual opening.--- ANYWAY The chart that I posted does indicate that the cams are on target and that I am VERY happy about. Thanks everyone, Charles | ||
| Ric Rainbolt (Ricrain)
New member Username: Ricrain Post Number: 41 Registered: 2-2002 |
The stated 0.5mm clearance is not the size of the shim, but the amount of the *LIFT* when proper shims are in place. IOW, the valve is considered open when it reaches 0.5mm of lift with the correct shims in place and the engine fully warmed up (and the cam to bucket clearances are all but taken up by thermal expansion). So, you subtract the shim clearance from 0.50mm and measure for that lift with a dial indicator. For example, if the intake has 0.20mm actual clearance when at room temp, then 0.50mm - 0.20mm = 0.30mm. Rotate the engine until that intake valve lifts 0.30mm measured from a ball indicator on the back of the shim, and that is considered the opening point. | ||
| Charles I Claussen (Atlantaman)
New member Username: Atlantaman Post Number: 5 Registered: 3-2002 |
lets try this pic again---  | ||
| Charles I Claussen (Atlantaman)
New member Username: Atlantaman Post Number: 4 Registered: 3-2002 |
BY THE WAY- just for kicks last night I tried another way of settign the cams just to verify if the numbers would be the same. I left the running valve shim in the motor--not the .5mm-- and put an air hose in the spark plug hole. I then applied about 20 psi of air and slowly turned the crank to listen for the exact moments when the valves opened and closed. At first I was really confised because the angles were way off but them I realized that with the regular shim in the car the valves are open a lot longer than with the thin one. I had to actually put allhte info into my CAD program and plot it but as you will see the results are the same.. I will include the drawing for what it is worth. Charles | ||
| Steve Magnusson (91tr)
Member Username: 91tr Post Number: 629 Registered: 1-2001 |
That's right Peter -- the valve opening/closing positions are usually spec'd at some small amount of valve lift so that you're operating at a point where the "lift vs angle" curve has a greater rate of change. At zero valve lift, the lift vs angle rate of change is so small (ideally 0) that this just adds a lot of uncertainty in trying to determine the angle you're at so it's not any "better" trying to measure/set things there. | ||
| '75 308 GT4 (Peter)
Intermediate Member Username: Peter Post Number: 1740 Registered: 12-2000 |
I never understood the reason behind setting clearance at 0.50mm for timing purposes. My thinking was that at that clearance, the valve suddenly opens, instead of slowly ramping up. And that the degrees given are the points of that sudden opening. True? Charles, just think of this motor as two 4-cylinder motors joined together at the crank. What you do for one, you do the exact same to the other. | ||
| BretM (Bretm)
Intermediate Member Username: Bretm Post Number: 2081 Registered: 2-2001 |
This is the only part of this whole rebuild that intimidates me. Damn, I really don't want to get to this phase of it. | ||
| Kelly J. Vince (Tifosi1)
Junior Member Username: Tifosi1 Post Number: 180 Registered: 2-2002 |
Charles, The way I did mine and it works is that the marks must be DEAD ON. If they are not then you have to readjust the dowel marks on the cam Sprockets. Ask Matt Boyd, he actually put picture out to show his exhaust was about one click off. When you finish and have rotated the engine a couple of times, This takes the slack out of the belts and evens up the cams. When you are at the top dead center mark on the fly wheel, then all cam marks should be dead on. please see Ric Rainbolts web site for instructions. My 2 cents. Kelly | ||
| Paul Newman (Newman)
Junior Member Username: Newman Post Number: 110 Registered: 12-2001 |
Just curious Charles, are you using different shims for '0' lash when adjusting your timing, assumunig you are taking your lift specs at the bucket. I would consider the engine to be 2 4 cylinder engines sharing the same crank when checking and adjusting the 5-8 bank. Ill be checking mine as well during reassembly. Im surprised they were that far off. Now I really want to check mine. | ||
| Charles I Claussen (Atlantaman)
New member Username: Atlantaman Post Number: 2 Registered: 3-2002 |
sorry--I think I have started off wrong--lets try this again 1) yes-you do set all 4 cams at the TDC 1-4 location and by the marks on cams lining up to those on the cam bearing cap for the initial setting. 2) this is not the final setting as these marks are not "dead nuts on". 3) with a degree wheel and dial indicator on piston, I found the exhaust cam 1-4 to be off by 4 degrees and the intake to be off by 5 degrees. 4) the 1-4 bank is now dead accurate but as suspected the lines are now slightly out of place--DO NOT CONSIDER THEM TO BE PERFECT!! Now back to the original problem---- Side 1-4 is now set---to do side 5-8 do you reset timing wheel to work at TDC 5-8 and use the same chart in the service book? do you have to reverse the angles? | ||
| Bill Sebestyen (Bill308)
Junior Member Username: Bill308 Post Number: 133 Registered: 5-2001 |
I believe all 4-marks on the cams should line up with cylinder 1 at TDC on the compression stroke (cylinder 1 valves are closed at this time). | ||
| Kelly J. Vince (Tifosi1)
Junior Member Username: Tifosi1 Post Number: 179 Registered: 2-2002 |
You rotate twice and make usre the marks you the bank you are doing line up. Of course do not disconnect both belts at the same time. So, change one belt rotate twice or 4 times how ever many make you feel good, then do the other bank. When all 5 marks line up. Put it back together you are there. Kelly | ||
| Charles I Claussen (Atlantaman)
New member Username: Atlantaman Post Number: 1 Registered: 3-2002 |
Before I proceed with my cam timing, I wanted to verify the proceedure because all reference material only deals with cyls 1-4 and not clys 5-8.. After you set the cams on 1-4 bank, do you rotate the motor to TDC 5-8 and repeat the same proceedure on 5-8, or do you set the timing off of the 1-4 tdc somehow? |