re. setting valve clearances
Discussion
Dan,
Checking valve clearances is really not too difficult, but for the uninitiated, it can be a quite a task. It involves removal of the cam covers and is best performed as a two person job. One person will have to check the clearance while the other manually turns the crank pulley to rotate the camshaft so each valve may be checked. Loosen the spark plugs to make hand rotating the engine easier. The service interval on checking valve clearances is every 10k mi.
Using a feeler gauge, check the gap between the 'heel' of the cam lobe and the 'cam follower' or tappet. You want to find a clearance of 0.005-0.007" for the intake valves and 0.010-0.012" for the exhaust valves. keep changing the feeler gauge until you find which one will fit snugly into the gap. Do this for each of the 16 valves (8-intake/8-exhaust) and record the difference of the actual gap subtracted from the specified gap measured for each valve. If the measured gap is between the clearances stated above, your valves are ok.
If not, you must remove the timing belt and cam carrier (you'll need an E10 socket)from the head and using a micrometer, measure the thickness of the shim sitting on top of each valve stem and record it's thickness. Do this for all 16 valves.
Now, you need to add the difference you previously recorded to the actual thickness of the shim for that particular valve to get your final values. These are the size shims you will need to order and install in order to achieve the correct gap. If you are using Aircraft Grade Form-a-Gasket to seal the cam tower to the head, this shim size will work as Form-a-Gasket is a 'Zero Tolerance' sealer, meaning it has no discernable thickness. If you are using Loctite504 to seal the carrier to the head, you will need to add an additional 0.0015" to the thickness of your shim to allow for the thickness of the Loctite.
Run the math calculations for all 16 valves and compare the size shims you need with the shims you already have. You can usually move some shims around and reduce the number of shims you'll have to order. Also, if you have a shim which is within 0.001" thicker than the size you need, you can use #600 sandpaper and placing it and the shim on a small mirror, you can sand the shim to the desired thickness. It takes about 10 minutes to sand away 0.001", so if they are thicker than 0.001" of your needs, it is more efficient to just order the new shim.
Once you have all the correct size shims, place them in their respective valve collet on top of the stem and refit the cam carrier using either Form-a-Gasket or Loctite 504 to seal them. Now, you must check the gaps again to insure that the proper gap has been achieved. If not, you have to pull the cam carrier and start all over again.
Once all gaps measure correctly, refit the cam covers, using a new gasket and sealed with Hylomar. Make sure your crankshaft is 90° off TDC and turn your cam sprockets so the dots on each align. Now turn the crank pulley 90° back in the opposite direction you turned it before back to TDC and re-install you timing belt and set the proper tension. If you have a distributor operated ignition, you must also align the ignition sprocket when installing the belt. Be sure to recheck your timing belt tension in the next 500 miles.
This procedure is complicated, but not that difficult. Attention to detail and accuracy will pay off with a much smoother running engine. If you have never done anything like this before, it's best to have a helper who has. Serious engine damage can occur if you're not sure what you're doing, in which case it would be cheaper to let a shop do it. Hope this helps...Jim '85TE
>>> Edited by lotusguy on Wednesday 13th November 04:18
Checking valve clearances is really not too difficult, but for the uninitiated, it can be a quite a task. It involves removal of the cam covers and is best performed as a two person job. One person will have to check the clearance while the other manually turns the crank pulley to rotate the camshaft so each valve may be checked. Loosen the spark plugs to make hand rotating the engine easier. The service interval on checking valve clearances is every 10k mi.
Using a feeler gauge, check the gap between the 'heel' of the cam lobe and the 'cam follower' or tappet. You want to find a clearance of 0.005-0.007" for the intake valves and 0.010-0.012" for the exhaust valves. keep changing the feeler gauge until you find which one will fit snugly into the gap. Do this for each of the 16 valves (8-intake/8-exhaust) and record the difference of the actual gap subtracted from the specified gap measured for each valve. If the measured gap is between the clearances stated above, your valves are ok.
If not, you must remove the timing belt and cam carrier (you'll need an E10 socket)from the head and using a micrometer, measure the thickness of the shim sitting on top of each valve stem and record it's thickness. Do this for all 16 valves.
Now, you need to add the difference you previously recorded to the actual thickness of the shim for that particular valve to get your final values. These are the size shims you will need to order and install in order to achieve the correct gap. If you are using Aircraft Grade Form-a-Gasket to seal the cam tower to the head, this shim size will work as Form-a-Gasket is a 'Zero Tolerance' sealer, meaning it has no discernable thickness. If you are using Loctite504 to seal the carrier to the head, you will need to add an additional 0.0015" to the thickness of your shim to allow for the thickness of the Loctite.
Run the math calculations for all 16 valves and compare the size shims you need with the shims you already have. You can usually move some shims around and reduce the number of shims you'll have to order. Also, if you have a shim which is within 0.001" thicker than the size you need, you can use #600 sandpaper and placing it and the shim on a small mirror, you can sand the shim to the desired thickness. It takes about 10 minutes to sand away 0.001", so if they are thicker than 0.001" of your needs, it is more efficient to just order the new shim.
Once you have all the correct size shims, place them in their respective valve collet on top of the stem and refit the cam carrier using either Form-a-Gasket or Loctite 504 to seal them. Now, you must check the gaps again to insure that the proper gap has been achieved. If not, you have to pull the cam carrier and start all over again.
Once all gaps measure correctly, refit the cam covers, using a new gasket and sealed with Hylomar. Make sure your crankshaft is 90° off TDC and turn your cam sprockets so the dots on each align. Now turn the crank pulley 90° back in the opposite direction you turned it before back to TDC and re-install you timing belt and set the proper tension. If you have a distributor operated ignition, you must also align the ignition sprocket when installing the belt. Be sure to recheck your timing belt tension in the next 500 miles.
This procedure is complicated, but not that difficult. Attention to detail and accuracy will pay off with a much smoother running engine. If you have never done anything like this before, it's best to have a helper who has. Serious engine damage can occur if you're not sure what you're doing, in which case it would be cheaper to let a shop do it. Hope this helps...Jim '85TE
>>> Edited by lotusguy on Wednesday 13th November 04:18
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