NP993

While you're torquing the heads/cam housings/head studs. I haven't built 250 motors, just a fraction of that, but in several instances it was important to verify during torquing that the cams weren't binding and were rotating without any areas of resistance.

pinogg

If you have an idea what is going on with my engine please let me know. And if it means you are going to be cruel, by all means go for it. I can take critism and it may help me solve the problem. You seem to be very knowledgable of these engines. Any advise would help I spent alot of money to get this engine to where it is now and believe me my feelings won't be hurt if you critisize as long as I resolve the problem.
Let me ask you a question, when everything is at TDC and the cam points are facing upward are cylinders 1 and 4 lifters set at the same time to 0.1, remember I went to mechanical lifters.

race911

Right, I saw that in your earlier post. I've nearly always assembled the heads onto the cam towers prior to mounting them on the engine. Can't say I've ever had an issue either with the earlier 3 bearing housings, or the later 4 bearing ones.

pinogg

I also assembled the heads to the cam towers prior to mounting the heads to the cylinders

pinogg

Just as additional information I had the heads machined to the exact height of each other about 6 thousands so I'm sure there is no bind with the cam

bobt993

Ken is giving you some good advice. One thing I learned during a couple of engine builds is check and recheck and check again. The torque procedure is real critical to follow and is outlined in the engine build process. You can also check on P-car work shop. He has a nice step by step method to assembly of pistons, cylinders, heads etc. The time and parts to pull the heads/cams and recheck is minimal compared to any possible start up issues. You mention that you installed only one plug to each cylinder. That means you should not have any sense of compression when turning the engine by hand so something else is causing the issue.

race911

OK, now that I'm back I see we almost cross-posted here. If I'm reading this correctly, you've got a problem. If I'm not, then I'm brain dead after being up 12+ hours already............

So let's get to how I'm reading this: you say TDC, and the "lifters" (really, rocker arms with the adjustable foot that allows for valve lash) are .1mm at #1 and #4. IS THIS AT THE SAME TDC? Because you need to rotate 360 degrees from #1 TDC to get to #4 TDC, and set #4 lash to .1mm. (Similarly, #6 TDC is 120 degrees from #1 TDC, etc. until you roll 720 degrees and get back to #1 TDC.)

If so, you've done what many of us have--given yourself two 3-cylinder engines on a common crank! One of which will be horribly off on both ignition and injector timing. (But amazing how they'd sorta run if equipped with carbs or MFI.)

Clarify that when you've got a chance, and we'll go from there.

pinogg

I removed all rocker arms and the engine spins freely without any binding actually it turn quite easy so do you think my pistons are hitting the valves

race911

Sure sounds like it. Now, unless you're ahead of me, go back to what I said earlier--install the #1 intake only and rotate to see it there's binding. If not, install #1 exhaust and rotate. If not, install #4 intake and rotate.

Then, since I'm still not sure you didn't time #1 and #4 to operate simultaneously, if we're to the point you've installed #4 and are rotating, look to see that #1 intake is NOT opening at the same time #4 is. If so, you need to re-time the 4-5-6 cam again.

race911

And to be clear on the above, if you note any binding as you're adding valves to operate with the installation of these rockers, you've got to take the heads off and check valve-to-piston clearance.

What's the timing spec on these cams? With all the engines I've done over the years, I've only done a handful (and I mean less than 5) 3.6L engine with non-stock cams. Consider an old "S" cam from a 2.0-2.4L car would have a TDC timing setting of ~.200". Compared to the nominal amount used on any plenum intake engine.

pinogg

Hi I'm back and have done alot of testing the valves I believe do hit the piston.
My question is I had the cams reground by Dorethy Cams so he used my original cams to give me a super-cup specs. He told me that they should be set at 2 mm . Will the porsche cams tools still work cause that is what I used to time the cams

geolab

Reground is a misleading word, I think.
The little I remember from 993 engine performance upgrades, is that reworked cams for higher
rpm's should open the valves more, and longer, if the original piston heads were used. Thus the cam lobes should be longer, and their
top edge thicker, for a longer valve opening.
Maybe if bigger valves are used, thus reworked heads? there is no need for higher lobes, I do not have a clue what the new cams have as specs.
Isn't the guy who reworked the cams, the one who has the perfect answer?

Toga

Interesting! This forum has plenty of "ressources", and I'm sure the specialists we have here will help you find the problem. For my information: How did you come to that mod, and where did you get the necessary infos before starting the job?