Quote:
Originally Posted by ErrieKruger
Grady - PS - what would a difference of 100F ambient temp make on these within 0.001 mm measurements ? Co vz Az.
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Only if you take the measurements outside
The crankshaft, the digital micrometer and all your ‘standards’ should all be at ambient (indoor) room temperature (mine are calibrated for 20C, ~68F).
It is absolutely critical to let the crank and instruments temperature stabilize – 12 hours should do, 24 is better.
Do not handle without gloves.
Do not re-clean with anything that evaporates (solvent, brake-clean, water, etc.)
Simply wipe your preservative oil (WD-40?) with a clean, dry lint-free cotton cloth.
Only handle the micrometer with gloves and on the insulating grip.
Only adjust the micrometer with the friction nurreled grip.
Make double-sure the micrometer and standards are at the exact same temperature.
I found it useful to also have some good gauge blocks either sides and around the Porsche limits that I was measuring.
Rectangular gauge blocks are much easer to use when checking the micrometer.
I recommend you only use the standards for checking the micrometer.
If out of spec (and new should not be), have a ‘professional’ do the adjustment.
You will find measuring a cylinder to 0.001 mm (0.000,039 inch) is not easy.
Even your breath temperature can change the reading.
It will take a lot of practice.
You will make a lot of measurements you will not use.
I’m sure there are some better instructions on the internet but….
Make sure the anvil and spindle are clean.
Never tighten with more than the force of the nurreled ratchet.
You want the micrometer to just barely slide with a bit of resistance across the diameter.
If you ‘cock’ the micrometer to either side of perpendicular, it will not slide.
You must be very careful ‘approaching’ the journal, the carbide ends of the micrometer are a LOT harder than the journal and can damage the journal.
Unless you get the
really expensive ones, reading the 0.001 mm digit is with the vernier.
Practice makes perfect to avoid parallax variations.
You will find the journals will have a ‘high’ and ‘low’ around the perimeter.
You want to locate and record both.
You will occasionally find a ‘taper’ to the journal.
This is usually from a slightly bent connecting rod.
You are also going to want a good (minor division = 0.001 mm) large dial indicator.
You will use this for measuring the crankshaft ’run-out’.
More on that later.
You will also use it for many measurements in the transmission.
Visual inspection is also critical.
You want to find every flaw, scratch, dent, etc.
Of particular importance are the radiuses where each journal meet the ‘cheek’ of the journal.
They must be ‘flaw free’ or risk a broken crankshaft.
I use a little 10X hand microscope from Radio Shack.If you find something suspicious, you will want an expert ‘second opinion’ and then possibility ‘non-destructive testing’ (Magnaflux, Zyglo, etc.)
You will find it VERY valuable for the machine shop experts to realize YOU can measure at least as well as they can – or better.
You will get their best work.
Can you post all the numbers from the crankcase?
What is the engine number (green arrow below)?
It may be in the range: 6114001 on.
(Ignore yellow.)
Here is the type number and build number (red arrow above).
What is the engine type number?
It may be 911/07.
What is the engine ‘build number’?
It should be just below the type number.
What are the case-half mating numbers?
It is on top of the crankcase, at a center case bolt between the middle cylinders (#2 & #5).
Usually 2-3 digit matching numbers.
What are the two (different?) casting dates?
They are on the front (pulley) end of the case.
They are a circle with a 2-digit year (70 or 71) and a series of dots around the perimeter of the circle.
What are the two casting numbers on the lower sides of the crankcase.
You can’t miss them.
911.101.101.2R 911.101.102.3R or something similar.
Can you use your great photographic skills to post some really good images of these?
Best,
Grady