Modeling clay

[OldTee]

I am going to check my valve clearance on all cylinders since I am using a special grind cam and new P&Cs. I did a deck height check and it was OK. My question is what do you use to keep the clay from falling off the piston during the check, or do you attach the clay to the valves? Curil T?

[BURN-BROS]

the check should be done on a clean and dry piston. the clay will naturally stick to it.

[Porschekid962]

Clay is an option, some have used thin solder and there are some other methods. I prefer math honestly. If you have an accurate measurement of everything in your motor than the only reason to use clay or solder would be a way of backing up your math. Plus once you have your measurement mathematically you can account for material stretch at operating temperature again using math. I think the solder and clay method is purely to give people peace of mind after they have rebuild their motor. I admit I have made one mistake before, I did not properly flush out all the oil galleys. Lesson learned, I cant wait to rebuild the motor again and fix all the mistake the previous builder made, it leaks like a pinata after being hit by a bat. Doesnt matter though, they have been doing this porschay thing for a long time and I dont know anything, riiight......

Curil T, Yamabond/Hondabond/Mitsubishibond are your friend! Loctite also has an awesome array of products just dig a bit deeper.

[Henry Schmidt]

Originally Posted by Porschekid962

Clay is an option, some have used thin solder and there are some other methods. I prefer math honestly. If you have an accurate measurement of everything in your motor than the only reason to use clay or solder would be a way of backing up your math. Plus once you have your measurement mathematically you can account for material stretch at operating temperature again using math. I think the solder and clay method is purely to give people peace of mind after they have rebuild their motor. I admit I have made one mistake before, I did not properly flush out all the oil galleys. Lesson learned, I cant wait to rebuild the motor again and fix all the mistake the previous builder made, it leaks like a pinata after being hit by a bat. Doesnt matter though, they have been doing this porschay thing for a long time and I dont know anything, riiight......

Curil T, Yamabond/Hondabond/Mitsubishibond are your friend! Loctite also has an awesome array of products just dig a bit deeper.

Math makes some assumptions that practical testing doesn't.
For example, clay can tell you if a valve pocket in a piston is machined a few degrees off center. Does it happen allot? no, but I've seen it more than once.
Clay can also tell you if a cam is ground improperly. Math can not. Are most cams ground within a usable tolerance? yes, but I have also seen cams ground so far off that starting the engine would have resulted in obscene operation and an unbelievable nightmare to diagnose.
Calculate your set up with the best numbers you can, then verify the conclusions. It's the wierd once in a life time situation that you'll find with clay testing.

I don't know who built our previous engine but quite often even a proper build can leak. In the early 90s the Porsche factory was averaging about 4% of their new engines leaking right on the dyno.
You don't get good with time alone and the number of engines built is no guaranty of excellence but discounting experience shows the arrogance of youth. We have well over 400 911 engine rebuilds yet I believe our product gets better all the time. It's the learning experience that leads to excellence.

[Porschekid962]

Which is exactly why you measure everything and then go through with your calculations. I could care less what the Porsche factory was doing with leaking motors, I know how I deal with them. A product can always be improved upon which is the reason the air cooled motors lasted so long in the first place, constant improvement. Just because I am smart and methodical does not make me arrogant.

Cheers

[Henry Schmidt]

"I could care less" is a phrase that always leaves me with a feeling that a person has tabled their arrogance and is willing the learn. "I could care less" is often followed by "because I know everything" whether stated or implied.

Just for fun, please explain to us your method for measuring valve pocket depth and location as they relate to crank parallelity and individual valves at a full range of lift and duration.
While you're at it, please explain the tools you're using at home to measure cam lobes for lift, duration and lobe center. I assume you have an optical comparitor and a Cam Doctor at home, but most don't.

Even Formula One teams, perhaps the most technical form of engine development in the world, use clay modeling in their research, development and assembly. They can measure and perform complicated geometric and algebraic equations as well as anyone (they might even be smart and methodical) and still use some tried and true old school methods.

[OldTee]

Originally Posted by BURN-BROS

the check should be done on a clean and dry piston. the clay will naturally stick to it.

I am stopped dead in the water. Bottom assembled but Cams and rockers are still out being refurbished. Long lead time items to say the least. I was thinking about going ahead and preassembling up to the point of inserting the cams but, leaving the clay in place that long did not seem wise. The temps here in DC can be 70 but they can also be 105 and humid at this time of the year. So I wait and will try to do the assembly and measurements in one day from start to finish.