rogerkamp8817

Hi,

I'm doing a 993 3.6L swap into my 75 911s. I'm having issues with the motor swap, mainly the timing. Lots of details and parts I'm glancing over, such as AEM infinity standalone engine management, COP's, Clewett cam sync and crank sensors, professionally built custom wiring harness, etc. Long story short, we've eliminated most other things that could be causing my issues. The main issue is that the motor does not run smoothly when z1 is at TDC and appears to run better when motor is retarded at 30-45 degrees. Again, we're confident the AEM infinity has the ignition timing setup correctly as I've had two different individuals with extensive background in AEM try to help me with this swap and they've also reached out to their contacts they have. I'm getting 180-190 psi compression on all 6 cylinders.

I believe my motor was manufactured when during the 964 to 993 transition year so it may have parts from both. With that said, can someone please point me to info or help me check my cam timing? I'm located in Orange County, California. What tools do I need and what steps can I follow to check the timing? Photo attached showing my particular motor. My motor is running Webcam's 993 RS Euro cams (installed by previous owner's engine builder). What should the cam timing be set at for this particular cam? Everything else about the motor is stock (only top end was rebuilt by previous owner, in addition to adding the webcams).

Thanks in advance.

rogerkamp8817

rogerkamp8817

We've reviewed the engine logs and the all sensors appears to be working. We've checked pins for the wiring harness and all pins to the coils appear to be in the correct order. We've checked all grounds.

Couple videos of the car running (poorly) can be downloaded thru my dropbox link here: https://www.dropbox.com/s/vk9d259nsh...5_691.zip?dl=0

wallra

here is how you check cam timing. I'm also COP on a 964 with Richards setup.

Churchill

You've already got the earlier style cam sprockets on your engine. Checking the timing is pretty straightforward. You'll have to remove both upper valve covers and install a mechanical rocker arm to use with the dial gauge.

Churchill

Did this engine run right for the previous owner? If so, it's almost impossible that you have a cam timing problem. Cams can't exactly un-time themselves. You appear to have an ignition and timing problem, and the main things you changed on the engine from stock are...ignition and timing.

rogerkamp8817

Thanks for confirming i have the earlier style cam sprockets. this motor had the top end rebuilt by the previous owner never ran after top-end rebuild. can't say if it was timed right since it never ran after that.

rogerkamp8817

I think my first step is to check timing. If it's off,then, my next step is to buy additional tools to adjust cam timing.

To check cam timing, I would need these tools:
-Z block and dial gauge or SR098 Cam Timing Fixture
-TDC indicator or SR022
-Anything else? Do i need a mechanical rocker to do this check or not needed at this stage?

To adjust cam timing, same tools shown above but also the following
-P9551/9552
-SR9582
-SR9401
-With these tools, would i need a mechanical rocker?

Thanks

Churchill

Yes you need a mechanical rocker. Should be able to buy one off the Pelican classifieds for $10-$20. Can be a core. Luckily rocker shaft diameter is the same between 993 & earlier models.

Mike J

You will always need a mechanical rocker since you cannot measure correctly with a hydraulic lifter. That mechanical lifter will need to be ground a bit to fit - its obvious once you try to fit it. You only need the dial indicator to sit on the top of the spring, I find the standard z-block is a bit restrictive (its designed for the cam carrier before the hydraulic lifters), so I use a steel plate and a magnetic base to position the dial indicator parallel with the valve stem, with a slight preload. You will need to contact Webcam to find out the specific timing for the 993 RS Euro cam - not sure what lift is expected at TDC. The stock cams are 1.00mm. You can verify what its been set to with just the dial indicator and tools to make sure there is tension on the timing chains. You will also need the tool to hold the sprocket still while you torque the cam nut, but you may not need that if the timing is correct.

If the engine has never run correctly, you should check the timing. It can be done in the car, it takes a bit of doing but its easier than pulling the engine out.

Cheers,

Mike

rogerkamp8817

In speaking with WebCam today, it sounds like their 993 RS Euro cam should have 1.8 mm of lift so that's what I'll be ideally looking for. The tolerance for the factory cam is 0.15 mm if recall so assuming it's the same tolerance, an acceptable range would be 1.65 - 1.95 mm.

For comparison, the closest DC cam appears to be the DC 21 (identical duration at 0.050" but slightly different on the other specs) . Although the specs aren't identical between these two cams, DC's website shows their DC 21 has a lift of 2.0 mm. I think the 1.8 mm that Web cam gave me is in the right ball park.

I'll look out for a mechanical rocker. Will any old 911 rocker do or does it have to be a specific 964 3.6L mechanical rocker?

If the standard z-block is too tight, will the Stomski Racing SR098 tool work or same issue? https://www.stomskiracing.com/produc...timing-fixture

This Stomski Racing SR9582 tool appears to be the right tool for the cam sprocket bolt, eliminating the need for the factory tools: https://www.stomskiracing.com/produc...cket-bolt-tool

Motor is out already. Third time pulling it out and it took me about 2.5 hours this last time.

rogerkamp8817

Couple thoughts and questions:

1) Can i get good compression if cam timing is off?

2) Before going as far as checking cam timing, could i check leak down to give me a ballpark idea whether or not the cams are timed properly? For example... z1 at tdc should give me very little leak down (or least amount) for cyl 1 at tdc, z1 at 120 degrees should give me very little leak down when cyl 6 is at tdc, z1 at 240 degrees should give me very little leak down when z1 is at 240 degrees, etc. Obviously this won't be accurate for measuring actual cam timing, however, is my logic correct and can approach it this way to see if my cam timing is in the right ballpark?

Churchill

It'll take you less time to check cam timing than do a leakdown. Plus I'm not sure your theory works in practice, because the valves are closed for most of the rotation of the cam -- i.e. cam timing could be off but you'd get good LD numbers. The only time valves open is when the cam lobe rotates onto the rocker, and you can simply look at the cams and see that around 2/3rds of the time the rockers are not being activated by the lobes.

rogerkamp8817

Got it, thanks for the helpful responses.

Have the z block and a dial indicator on order. Working on finding a mechanical rocker now.

ekimerpud

I've never seen a fan shroud like that. Can I ask where you got it?