[Vwdiesel] The Story of my Engine, its controversial headskim, and the offensive rebuild, {A bit long}

[lbaird119 at aol.com]

  Can't say that I disagree with much of what you did at all.  I had a shop bore and hone start using oil at 15K due to an incorrect hone.  Had it torn down and supposedly honed only to repeat (with new compression and oil rings, TS second rings).  FInally did it myself, the third time.  Used my 3 stone hone.
  You CAN get a decent cross hatch but it requires moving up and down rather quickly with a variable speed drill going fairly close to the slowest sustainable speed.  I also lean closer to the 180 ring placement compared to the 1/3.  Major exception is a horizontally opposed engine where they recommend about a third but only in the top half.  I kept to the top half on those but used a wider spacing, closer to 180.  Found out that the depth of the cross hatching is important for ring lubrication.  Shop didn't have it deep enough (coarse enough) so the rings wore prematurely.  Diesels tend to need more coarseness than gassers, which is where all the ultra fine grit honing ideology come in.
  I'd say you did well.
     Loren



-----Original Message-----
From: Mark Shepherd <mark at shepher.fsnet.co.uk>
To: vwdiesel <vwdiesel at vwfans.com>
Sent: Wed, May 15, 2013 2:07 pm
Subject: [Vwdiesel] The Story of my Engine, its controversial headskim, and the offensive rebuild, {A bit long}


HEAD-SKIM
ere’s my engine rebuild details:
ought engine in a 1985 Quantum wagon 6 years ago. Ran it and the car for nearly 
 year. Retimed engine to get me from 36mpg imp to 45-48imp. 
ead gasket blew. 
id my hand skim of head on plate glass, leaving on manifolds, cam, etc. I did 
ot need to mess about with the precups, unlike the choice of many machinists 
ue to the 
oft/hard metal interface, and they all ‘machined’ along with the tips of the 
xhaust manifold! 
 did it like this because I wanted to avoid any possible flexing and reflexing 
f the head during the removal-skim-replacement process. 
I admit now that I probably overdid the skimming, and probably used my 
ounter-weight, of a bar of steel 24” x 4” x1/2”, end tucked under the cam a 
ittle too late to 
revent slightly more being machined off the head along the manifold side, 
ompared with the injector side...
et, 5 years on no issues, other than the knocking that I’ve mentioned before 
rom the valve faces being brought closer to the pistons, and indeed I suspect 
atching up 
ith the piston face both after TDC, and being caught by piston before TDC. This 
ust be the initial reason that VW threw away the heads for all those years 
ather 
han skimming them... 
 did nothing else to the engine, other than to peer down the bores and notice 
light wear.
ENGINE REBUILDt long
 years on ( 3 years ago), I had a few starting issues, scattered over a couple 
f months, and needing a jumpstart mid journey a couple of times. The Automobile 
Association put it down to a weak starter motor, but they didn‘t have one[As it 
urns out fortunate]. A complete strip down revealed half a cup of old engine 
il, that must 
ave accumulated over the years from leaking rocker covers. A few weeks respite, 
efore the flat battery reoccurred.
I built an adaptor for a compression tester, and did some tests, as the engine 
eemed to be turning over reasonably, as far as I could judge, compared with my 
ther 
uantum TD. I think the results were 190, 250, 250, and `290, or thereabouts. 
hus I decided, that even if my lead filled injector body adaptor was reading 
ow, the 
ompression spread was out of spec, so a rebuild was necessary. 
Ordered some rings from Autohause $22 per set of 4 pistons, Grant brand, 
tandard size, and some shell bearings. Couldn’t justify the more expensive, 
ssumed 
hrome ones , as the whole car had only cost $45.Couldn’t contemplate oversized 
ings and rebore oversized pistons etc.
Left block in the car. Sump off, pulled[pushed] pistons out of top of block, so 
aybe top of bore not too bad... Piston crowns did indeed have both inlet and 
xhaust 
alve imprints. Exhaust most prominent and #1 and #4 the ‘worst’ #2 and #3 mere 
host like shadows in the carbon. All imprints were concentric rings, 
emonstrating 
hat they were a product of 1000’s of hits of rotating valves. 
All I did was to scrape the ridge from the circumference. Looked worse than it 
as, as only a couple of thou deep when checked. No wrist bearings, big end 
earings, 
r crank bearings showed enough wear to be replaced, indeed most showed no wear 
t all. Thus I did not make the mistake of replacing, and introducing lesser 
atched parts. 
RINGS:
 out of 12 rings were stuck in Careful removal, revealed extent of their 
ear... Top compression rings had gaps up to an astounding 160 thou, with 
everal mm being 
emoved from their radial thickness. Middle rings slightly less, and oil rings , 
round down almost to the wires. Apart from carbon infill, those hard ring 
arriers perfect. 
nly one piston showed any skirt scraping, and that was only to be expected with 
he stuck rings. I felt new rings would fix this. Put a set of new rings into a 
ore to 
heck specs. Fine except for the top ring at the top was just inside the limit. 
o way I’m going to spend money on rebore etc, and after all new rings had to be 
n 
mprovement, and apart from the final straw of rings sticking, these rings had 
aken years to get to this stage..
. Now for the apparently contraversal treatment of the cylinder bores, which 
plit the GTD forum down the middle, including the moderators...
THE HONE. 
 do have access to a spring tripod type stone hone, but I thought it a great 
pportunity to experiment, after all what harm could it do?
ere was my reasoning: 
he purpose of working on the bores of an engine is to create a trued up bore, 
nd a matt finish. The matt finish is to provide a window to break-in the rings, 
nd to get 
hem to hug the bores with a minimal, yet essential mutual wear. The purpose of 
he crosshatching is to allow lubrication of the compression rings
A rebore gives a nice mat finish,. 
I have my doubts about the 'perfection' of a machined hone, as an addition to a 
achined rebore, because it weakens the surface of the cylinders... Too much 
nurling 
eaves sharp edged mountains which level off further with break in, than mere 
eglazing and relatively few crosshatches do, which start off with resilient 
lateaus. 
Machine work is a modern mass-production invention that produces 'satisfactory' 
esults everytime. No books will tell you why you need 10000 crosshatchings, 
ather 
han 10, per stroke for lubrication. There seem to be plenty of people out there 
ho do ‘perfect by the book’ hones, yet still get oil burn issues. 
Remembering the old techniques of latheing up a piece of wood to fit the bore, 
nd covering with emery, I took this idea and brought it into the present time 
y using a 
nug fitting plastic bottle and glueing onto it some 600 grade emery/glass 
aper. 
eaving the bottle cap on, and holding the neck of the bottle I determined that 
 could create pressure to the abrasive fairly evenly around the bore of the 
ylinder as an 
pproach to the official tool, and ensure that in addition to the deglazing, I 
ould drop some strategically placed cross hatchings around the bore at the 
agical 45 
egrees, using a twist and thrust movement of my arms. Somewhat like the end of 
 karate punch. Changing hands to get some crossing... 
Using a drill to spin the abrasive stones must surely result in much less than 
5 deg hatching... 
PISTON RINGs
hen setting the rings about the piston, many books say spread the gaps about 
20 degrees around . Why? Why start an engine running with the rings at less 
han 
ptimum compression setting? I make that a third shorter route distance for the 
scaping gasses. If the rings do rotate, before deciding on a place to rest , 
hen there is a 
0% chance of compression getting worse. I always set the rings 180 deg apart, 
o start out at the best possible compression, and hopefully settle quicker, and 
efore 
he official starting position...
easembled and drove it, and reached over 50mpg for the first time. 
So what responses did I get? Varied. The power crazy Moderator said I couldn’t 
ossibly achieve the results of a proper tool, and spending $500 on the work inc 
ools 
as the way to go. Others full of praise. or sided with the $500man. Not 
onvincing me, he then pointed out that I did not cover the injection pump 
utlets 8op. What if 
ome grit got in there? Someone else said I could grenade the engine... Well a 
it of grit in the line would either pass straight out or get crushed by the 
igh carbon steel 
ozzles, and besides just exactly how fast did he think my wrist moves, compared 
ith a drill. What kind of an ‘anker does he think I am? I did have cloth down 
elow 
ores.
Further to their annoyance was because I also didn’t change the head gasket 
although I had one) as gasket leak was not the issue, and amazingly the gasket 
as a 
erfect fit ;o) Also, because I never torque beyond the plastic point of the 
ead bolts, they were also reused. 
efinitely never change the tensioner pulley, unless showing signs of wear, 
specially if it looks like an early one. As I never over-tension the timing 
elt, the pump’s 
earings don’t leak either.
inally I demonstrated and explained why reuse of heatshield is actually good 
or the head.... 
UPDATE:
conomy constantly beats book values: of 42.1mpg URBAN and 57.6mpg 
Constant90Kmh for the wagon
Urban 43; 47; 48, 44.5; Two trips 61.4; 59.5; These are the last 6 fuel readings 
iming is set to 0.57mm Injectors were set to 130bar. Recently had a smoking 
ssue on 
tart-up. Only for a matter of seconds and only from overnight rest. Removed 
njectors before using car, to catch problem and found one injector 3 or 4 bar 
elow the 
ther’s and one other spitting slightly. Fixed and reinstalled.

Mark
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