Engine Pull Thread

libbybapa · Post by **libbybapa** » Thu May 10, 2007 10:57 pm

Just for reference, the piston to cyl clearance with new pistons and bored cyl should be .001 inches (actually 1 thousandth). Be sure to stress that to the machinist as that is an uncommonly tight fit and some machinists who are not used to dealing with German precision seem to be under the impression that such a tight clearance will result in piston seizure. The wear limit is actually .0025 (or 2.5 thousandths). I assume that you measured the piston to cyl clearance as .025 inches which would be 10 times the wear limit.

Andrew

Post by **Fatmobile** » Fri May 11, 2007 1:25 am

From my experience the I-shaft bearings look good until about 150,000 miles.... but they don't usually look as chipped out as yours. That's extreme.

How do the I-shaft bearing surfaces look?
A VW diesel engine almost always has the original pistons at that time.
Think it ran good before, imagine how nicely it will run after a rebuild.

CoolAirVw · Post by **CoolAirVw** » Fri May 11, 2007 10:05 pm

libbybapa wrote:Just for reference, the piston to cyl clearance with new pistons and bored cyl should be .001 inches (actually 1 thousandth). Be sure to stress that to the machinist as that is an uncommonly tight fit and some machinists who are not used to dealing with German precision seem to be under the impression that such a tight clearance will result in piston seizure. The wear limit is actually .0025 (or 2.5 thousandths). I assume that you measured the piston to cyl clearance as .025 inches which would be 10 times the wear limit.

Although I goofed when I wrote 12 thousandths, I didn't goof when I wrote 25 thousandths. Man thats alot!

I dropped the block and crank off at the machine shop today. sounds like its gonna be a slow process.

libbybapa · Post by **libbybapa** » Fri May 11, 2007 10:13 pm

You can always clean the pile of mucky parts in the mean time.

Oh, and flush the cooling system 100 times...

Andrew

libbybapa · Post by **libbybapa** » Fri May 25, 2007 9:17 am

Goofing off or something?

Andrew

CoolAirVw · Post by **CoolAirVw** » Fri May 25, 2007 8:05 pm

libbybapa wrote:Goofing off or something?
Andrew

Went to Cincinnati. But was waiting on parts anyway.

Got big box of parts yesterday. Man its Christmas! I'll post some pics later.

CoolAirVw · Post by **CoolAirVw** » Fri May 25, 2007 8:55 pm

Machine shop, Machine shop, Machine shop, Machine shop Crank&Block Crank&Block Crank&Block Crank&Block Crank&Block

Machine shop I'm using is Precision Crankshaft in Lee's Summit, Missouri. Mark and Keith are "freinds" (work acquaintance) so being "loyal" I decided to use them. A year or so ago I asked if I could watch while they turned a crank or bored a cylinder and they agreed but I never got the time.

They said they could get the clearance tight (1 thousandth like Andrew said) although they gasped at how tight it's supposed to be.

Precision called and said my crank just needed polishing and that I needed .030 over pistons. I ordered parts and they showed up yesterday.

When I dropped the pistons off their machinist was balancing some pistons and he suggested I balance the crank/rods/pistons. In order to demonstate how off balance the parts usually are he weighed the new pistons.

He started off by saying they should all be within 1 gram.
Right out of the box my new pistons were...
519.9 grams
520.4
519.7
520.6

Maximum difference lightest to heaviest was .9 grams. He said, "Nice!"

Needless to say I'm not balancing the Crank/rods/pistons. Lucky for me he was talkative. He gave me a 20 minute lecture on the process. I understand more of the process now but I wish I could have recorded what he said.

Machine shop, Machine shop, Machine shop, Machine shop Head work, Head work, Head work, Head work, Head work,

Previously I was going to reuse the head as is but today I decided to take my head to the Machine shop and I decided I wanted a Vw specialist so I dropped it off at Vee Village in Kansas City. (long story why I didn't use them for the block & crank If you want to know PM me and I'll PM you the story)

I checked valve sealing by the ultra exact, super scientific method of spraying Wd-40 into the intake/exaust ports and seeing if it leaked through. It did. On my porsche 914 it didn't so therefore these valves must be worn out. I also checked my spare head (<a href="viewtopic.php?t=6397&highlight=" target="_blank">Spare Engine Disassembly Thread</a> ) but found it unusable. I'll update the <a href="viewtopic.php?t=6397&highlight=" target="_blank">Spare Engine Disassembly Thread</a> with what I found there.