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

[Mark Shepherd]

HEAD-SKIM
Here’s my engine rebuild details:
Bought engine in a 1985 Quantum wagon 6 years ago. Ran it and the car for nearly a year. Retimed engine to get me from 36mpg imp to 45-48imp. 
Head gasket blew. 
Did my hand skim of head on plate glass, leaving on manifolds, cam, etc. I did not need to mess about with the precups, unlike the choice of many machinists due to the 
soft/hard metal interface, and they all ‘machined’ along with the tips of the exhaust manifold! 
I did it like this because I wanted to avoid any possible flexing and reflexing of the head during the removal-skim-replacement process. 

I admit now that I probably overdid the skimming, and probably used my counter-weight, of a bar of steel 24” x 4” x1/2”, end tucked under the cam a little too late to 
prevent slightly more being machined off the head along the manifold side, compared with the injector side...
Yet, 5 years on no issues, other than the knocking that I’ve mentioned before from the valve faces being brought closer to the pistons, and indeed I suspect catching up 
with the piston face both after TDC, and being caught by piston before TDC. This must be the initial reason that VW threw away the heads for all those years rather 
than skimming them... 
I did nothing else to the engine, other than to peer down the bores and notice slight wear.

ENGINE REBUILDt long
2 years on ( 3 years ago), I had a few starting issues, scattered over a couple of 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 turns out fortunate]. A complete strip down revealed half a cup of old engine oil, that must 
have accumulated over the years from leaking rocker covers. A few weeks respite, before the flat battery reoccurred.

I built an adaptor for a compression tester, and did some tests, as the engine seemed to be turning over reasonably, as far as I could judge, compared with my other 
Quantum TD. I think the results were 190, 250, 250, and `290, or thereabouts. Thus I decided, that even if my lead filled injector body adaptor was reading low, the 
compression spread was out of spec, so a rebuild was necessary. 

Ordered some rings from Autohause $22 per set of 4 pistons, Grant brand, standard size, and some shell bearings. Couldn’t justify the more expensive, assumed 
chrome ones , as the whole car had only cost $45.Couldn’t contemplate oversized rings and rebore oversized pistons etc.

Left block in the car. Sump off, pulled[pushed] pistons out of top of block, so maybe top of bore not too bad... Piston crowns did indeed have both inlet and exhaust 
valve imprints. Exhaust most prominent and #1 and #4 the ‘worst’ #2 and #3 mere ghost like shadows in the carbon. All imprints were concentric rings, demonstrating 
that 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 was, as only a couple of thou deep when checked. No wrist bearings, big end bearings, 
or crank bearings showed enough wear to be replaced, indeed most showed no wear at all. Thus I did not make the mistake of replacing, and introducing lesser 
matched parts. 

RINGS:
7 out of 12 rings were stuck in Careful removal, revealed extent of their wear... Top compression rings had gaps up to an astounding 160 thou, with several mm being 
removed from their radial thickness. Middle rings slightly less, and oil rings , ground down almost to the wires. Apart from carbon infill, those hard ring carriers perfect. 
Only one piston showed any skirt scraping, and that was only to be expected with the stuck rings. I felt new rings would fix this. Put a set of new rings into a bore to 
check specs. Fine except for the top ring at the top was just inside the limit. No way I’m going to spend money on rebore etc, and after all new rings had to be an 
improvement, and apart from the final straw of rings sticking, these rings had taken years to get to this stage..

. Now for the apparently contraversal treatment of the cylinder bores, which split the GTD forum down the middle, including the moderators...

THE HONE. 
I do have access to a spring tripod type stone hone, but I thought it a great opportunity to experiment, after all what harm could it do?
Here was my reasoning: 
The purpose of working on the bores of an engine is to create a trued up bore, and a matt finish. The matt finish is to provide a window to break-in the rings, and to get 
them to hug the bores with a minimal, yet essential mutual wear. The purpose of the 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 machined rebore, because it weakens the surface of the cylinders... Too much knurling 
leaves sharp edged mountains which level off further with break in, than mere deglazing and relatively few crosshatches do, which start off with resilient plateaus. 

Machine work is a modern mass-production invention that produces 'satisfactory' results everytime. No books will tell you why you need 10000 crosshatchings, rather 
than 10, per stroke for lubrication. There seem to be plenty of people out there who 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, and covering with emery, I took this idea and brought it into the present time by using a 
snug fitting plastic bottle and glueing onto it some 600 grade emery/glass paper. 
Leaving the bottle cap on, and holding the neck of the bottle I determined that I could create pressure to the abrasive fairly evenly around the bore of the cylinder as an 
approach to the official tool, and ensure that in addition to the deglazing, I would drop some strategically placed cross hatchings around the bore at the magical 45 
degrees, using a twist and thrust movement of my arms. Somewhat like the end of a karate punch. Changing hands to get some crossing... 

Using a drill to spin the abrasive stones must surely result in much less than 45 deg hatching... 

PISTON RINGs
When setting the rings about the piston, many books say spread the gaps about 120 degrees around . Why? Why start an engine running with the rings at less than 
optimum compression setting? I make that a third shorter route distance for the escaping gasses. If the rings do rotate, before deciding on a place to rest , then there is a 
50% chance of compression getting worse. I always set the rings 180 deg apart, to start out at the best possible compression, and hopefully settle quicker, and before 
the official starting position...
Reasembled 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 possibly achieve the results of a proper tool, and spending $500 on the work inc tools 
was the way to go. Others full of praise. or sided with the $500man. Not convincing me, he then pointed out that I did not cover the injection pump outlets 8op. What if 
some grit got in there? Someone else said I could grenade the engine... Well a bit of grit in the line would either pass straight out or get crushed by the high carbon steel 
nozzles, and besides just exactly how fast did he think my wrist moves, compared with a drill. What kind of an ‘anker does he think I am? I did have cloth down below 
bores.

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 was a 
perfect fit ;o) Also, because I never torque beyond the plastic point of the head bolts, they were also reused. 
Definitely never change the tensioner pulley, unless showing signs of wear, especially if it looks like an early one. As I never over-tension the timing belt, the pump’s 
bearings don’t leak either.
Finally I demonstrated and explained why reuse of heatshield is actually good for the head.... 

UPDATE:
Economy 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 Timing is set to 0.57mm Injectors were set to 130bar. Recently had a smoking issue on 
start-up. Only for a matter of seconds and only from overnight rest. Removed injectors before using car, to catch problem and found one injector 3 or 4 bar below the 
other’s and one other spitting slightly. Fixed and reinstalled.



Mark