We have seen a lot of YouTube videos on Cam shaft timing. We are going to add ours to the mix. Our hope is that you can take the straightforward approach that we show you in this lesson.
Cam Shaft Timing where to start
If you have been following along with this engine build, in the last lesson, we set the heads and cam boxes. The chain boxes are on and we are ready to put in the cam shafts. The first part of timing the cam shafts is setting the depth of the chain gears.
Install both cams, oiling as you go, and place them with the dot up. Next, install the camshaft retaining plate. Do not use any sealant on this plate, the o-ring and gasket are enough if your plate is nice and flat. You can check your plate for flat, and sand if it needs it. Use some silicone lubricant on the oring and push the assembly gently in place. The bolts should go in easily by hand then tighten the nuts to 10NM.
Put on the thrust washer with the bevel facing in and start with three shims. Three shims is a good starting place. The shims measure .5mm and are the same shims used on the alternator.
At this point we do not install the key for the cam gear, we will get to that after it measures correctly. So push on the gear and pull back on the camshaft. Put on the timing gear next, on the one to three side the dish on the gear faces out. On the 4-6 side the timing gear dish faces into the camshaft.
Put on the large wave washer and the cam-shaft nut. Support the camshaft and tighten the nut, we will not torque it at this time, just get it tight and check the cam moves freely.
Chain Gear Depth
On the engine block, we left off the intermediate shaft cover. Using a depth gauge, measure the depth of the intermediate gear through this hole. Take this depth and add the thickness of our straight edge. With this number in hand, we can set up the straight edge.
The Stomski bar holder uses the same studs from the intermediate shaft cover plate. If you want to handhold the bar, that is possible, but the job is much easier with it held for you.
Start on the 4-6 side of the engine. Use a depth gauge with a good-sized foot, to stay square to the bar. On this engine, we want 77.14mm with a plus or minus of .25 of an mm. So for our engine, three shims were the perfect amount on this side. Replace or remove shims as necessary and re-measure.
When setting up for the one/three side you will need to check the factory manual for your model engine. For this 2 liter, the difference is plus 54.8mm so the depth we are looking for is 131.94 mm. We got that number by adding the 54.8 to the 77.14 of the other side with the bar included in this measurement. On this side, we needed to add one shim to get within tolerance.
Once the chain depth is set, we need to undo the gear again and add the keyway. Let one side of the cam shaft woodruff key lay down to help the cam Vernier gear get back in place.
Setting up the Engine for Cam Shaft Timing
The engine needs to be on Top Dead Center or TDC. Use the Z1 timing mark on the lower pulley and line it up with the case split. Now we can run the timing chain around the gear, adding the timing chain guides as you do. Make sure the gears go on in the correct direction. Pull down on the timing chain and add in the timing chain idler gear.
On the idler gear use some oil for lubrication and check that the oil bucket on the gear is facing up. Next, you can put tension on the chain with a dummy chain tensioner. There are many different styles of dummy chain tensioners. We have had ours a long time. One thing in common with all dummy tensioners is that they should never be used as a chain tensioner. Check our re-build on the chain tensioners if you have any doubt if yours are good!
Take your timing pin, making sure the thread is facing out, and find a hole in the cam gear that lines up. To check the cam shaft timing we have to have an intake rocker in on each bank, one and four. Lubricate the cam and the rocker as you put them in. Set your valve clearance to 0.1 of an mm
Tools you may need
Using a Z-Block and Gauge
Set up your z block and gauge on to the valve spring retainer. Make sure there are no obstructions to the long pin.
Your valve depth will vary for your cam and engine. The number on the cam will be in the spec books for your year, it can be a lot different for each. So you need to look it up, not just assume. For this engine, we are looking for 2.5mm at TDC. Find the depth by turning over the engine. Look at the timing mark, does it line up? No. Take off the cam nut and washer and pull the timing pin.
Line up the Z mark with the engine mark. Move your cam back into possession if it moved a bit. Now you can put in the timing pin in a hole that lines up. Put on the washer and nut and tighten the cam nut at this time. The torque on the cam nut is 110 Newton meters on early motors and 140 on late models. Run through the engine 360 degrees and recheck the timing.
Setting the Cam Shaft Timing on the other side
Set the rocker shaft with the 5mm Allen head on the open side. Oil the rocker and shaft as you install it. Make sure the rocker is free. Then set the valve clearance to 0.1 of an mm.
When you have set one side, the other side needs to match as close as you can to the number you got. There is often a range given by Porsche, and sometimes Porsche will give an optimum timing number. Either way the number you end up with needs to be matched on the other side.
Set up your Z-Block on intake valve on number 4 cylinder while at TDC. Run through the same process as bank one. Once you have tightened down the cam nut to full torque, run the crank through a full 720 revolution and check the timing.
Up-Next on Your Porsche Air-Cooled Engine Build
We are going to put in the timing chain tensioners and the rest of the rocker shafts. We have a full rebuild video on the non-pressure fed timing chain tensioners. You are going to need the special tool P214 or make one to keep your tensioners compressed to fit into the engine. More on that next!