"Blueprinting" VW heads
Geoffe Elias
I'm aware of the importance of keeping head chamber volume equal
across all the 4 cylinders as well as the benefits of a port and
polish job. But I am wondering about the techniques of cleaning up
the exterior fin area of the stock cast VW cylinder head.
Specifically, I would like to clean up the casting imperfections
(casting flash?) between each of the fins.
I look "down" into the head fins (from the perspective of the air
coming from the fan shroud) and I see places where it would seem that
the VW engineers intended for air to blow through. But deep in those
places are blockages by random "flash" (like the plastic flashing have
to trim away when you build a model airplane or such). My first
impulse was to get a small flat-headed screwdriver and rubber
mallet...but that didn't seem wise. What tool should I use to get
deep in there and clear out those places between the fins.
I know it seems anal but I am trying to blueprint the cooling design
of my 1776cc Type 1 engine (with Webcam 163 camshaft) so that I may
safely run a higher CR (9.2:1) while running pump (Premium) gas in
California. I am running the late Doghouse fanshroud with all cooling
flaps and all the other various cooling tin that everyone forgets
about.
I am also exploring getting heat barrier coatings applied to the
head combustion chamber by these guys:
http://www.replikamaschinen.com/ If the cost of getting those
coatings done is less than $300, I am certainly going for it.
Anyways, thanks for any advice on head fin cleanup as well as
highest CR for my engine.
Regards,
Geoffe Elias
'74 Super Beetle
Jan Andersson
> Hi Volks,
> I'm aware of the importance of keeping head chamber volume equal
> across all the 4 cylinders as well as the benefits of a port and
> polish job.
if this is a street car, do not polish the intake ports.
The exhaust and intake port flow should be in a certain relation to each
other, for the head to work well. (Exhaust flows less, 1target is a
certain percentage of intake flow, like 85% for example).
If you just go to town and hog the ports out as big as you can, you will
likely ruin the heads.
More flow can be found safely from a professional competition valve job.
(Including but not limited to what is called "3-angle valve grind" )
The valves and seats are ground to certain progressive angles (or a
controlled smooth radius), and the valve faces can be radiused too (but
only on one side.The exh is ground on the piston side, while intake
valves are radiused on the port side. If memory serves... )
There's more that can be done to the valves depending on their design.
> But I am wondering about the techniques of cleaning up
> the exterior fin area of the stock cast VW cylinder head.
> Specifically, I would like to clean up the casting imperfections
> (casting flash?) between each of the fins.
Yes, do it. Some cheap aftermarket "stock heads" have an obscene amount
of flash clogging up all passages.
> I look "down" into the head fins (from the perspective of the air
> coming from the fan shroud) and I see places where it would seem that
> the VW engineers intended for air to blow through. But deep in those
> places are blockages by random "flash" (like the plastic flashing have
> to trim away when you build a model airplane or such). My first
> impulse was to get a small flat-headed screwdriver and rubber
> mallet...but that didn't seem wise. What tool should I use to get
> deep in there and clear out those places between the fins.
I drill them. No shock of hammer blows.
> I know it seems anal but I am trying to blueprint the cooling design
> of my 1776cc Type 1 engine (with Webcam 163 camshaft) so that I may
> safely run a higher CR (9.2:1) while running pump (Premium) gas in
> California. I am running the late Doghouse fanshroud with all cooling
> flaps and all the other various cooling tin that everyone forgets
> about.
What is the octane of your premium gas?
9.2:1 is too much for that cam, unless it's pretty darn high octane gas.
Don't go over 9:1, and if you have the kind of fuel I think you do, you
need to stay in the 8.7:1 neighborhood.
You will need to slightly radius all sharp edges in the combustion
chamber. Also unshroud the valves in the chambers. Make chambers deep
and narrow, if you need more volume. Do not widen them. You want the
mixture to be concentrated in a tight, small area. It can be deep, but
not any wider than it has to.
You also want to run a very tight deck height. Between 1.1 and 1.3mm, NO
MORE. I'd rather try to get it closer to 1.1mm. Set that first, then
figure out how big your chambers need to be, to produce the CR you want.
Then work on the chambers to get there.
> I am also exploring getting heat barrier coatings applied to the
> head combustion chamber by these guys:
> http://www.replikamaschinen.com/ If the cost of getting those
> coatings done is less than $300, I am certainly going for it.
No personal experience. Some people say it works.
Jan
Jan Andersson
Oh yea, you can most likely run 1.25:1 rockers with that cam, for a
little more lift.
Randall
The link brings up all posts on RAMVA by veeduber (AKA Bob Hoover)
containing the phrase "casting flash".
http://groups.google.com/groups/search?hl=en&as_q=&as_epq=casting+flash&as_oq=&as_eq=&num=20&scoring=&lr=&as_sitesearch=&as_drrb=q&as_qdr=&as_mind=1&as_minm=1&as_miny=1981&as_maxd=1&as_maxm=4&as_maxy=2009&as_ugroup=rec.autos.makers.vw.aircooled&as_usubject=&as_uauthors=Veeduber&safe=off
Below is what the Google Groups search page looks like. It's pre-filled
with: group = rec.autos.makers.vw.aircooled and author = Veeduber. For
your particular search you would enter in the second box where it says
"this exact wording or phrase:" casting flash to return the same
results as the link above.
http://groups.google.com/groups/advanced_search?hl=en&safe=off&q=group:rec.autos.makers.vw.aircooled+author:Veeduber
Also, at Bob Hoover's Blog, once you get to the link below, use your
browser's search capability to do a search of the phrase "casting
flash". As an added bonus, the first page of the blog (dated Wednesday,
August 1, 2007) discusses a topic related to your other question about
heat barrier coatings.
http://bobhooversblog.blogspot.com/search?q=casting+flash
-- Randall
Geoffe Elias
Actually Bob Hoover's blog indeed was the inspiration for me
deciding to explore doing this to my own engine. But it was left to
the reader to fill in the exact details on how he performed the fin
cleanup on his cylinder heads (lots of Youtube videos on porting/
polishing but not on this). Hoover did say he used a pneumatic riffler
but I do not have that tool. The other suggested tool was a hand saw,
but there was an area where my saw could not quite break through and
was about to resort to using a rubber mallet to help the tool punch
through but then decided to seek other options...
Geoffe
-74 Super Beetle
> containing the phrase "casting flash".http://groups.google.com/groups/search?hl=en&as_q=&as_epq=casting+fla...
>
> Below is what the Google Groups search page looks like. It's pre-filled
> with: group = rec.autos.makers.vw.aircooled and author = Veeduber. For
> your particular search you would enter in the second box where it says
> "this exact wording or phrase:" casting flash to return the same
> results as the link above.http://groups.google.com/groups/advanced_search?hl=en&safe=off&q=grou...
Geoffe Elias
Thanks for the drill idea! Will look at long enough drill bits to
make this happen.
As for the main question about CR:
Over where I am at, it is 91 octane. My current CR is 8.2:1. I
agree that a jump to 9.2:1 is steep, but I was wondering if the use of
heat barrier coatings could justify that jump.
Problem is that the engine is running a bit too cool, even cooler
than the stock 1600 (with the same cooling setup). I can't give any
real temp numbers but only a comparative observation is based upon the
use of a Berg oil dipstick temp sensor device.
-Geoffe Elias
'74 Super Beetle
On Apr 8, 4:36 pm, Jan Andersson <bugf...@spamtrap.rocketmail.com>
wrote:
jtbartlett
>
> - Show quoted text -
I think the weapon you are looking for are diamond rifflers. Cheapo
chinese files coated with industrial diamonds. These really eat
through the casting flash like butter. You can get a set or 3 on Ebay
or through the larger cheapo tool distributors. Notice the word cheapo
being emphasized? These really are just that. I think I paid seven
bucks for a set of a dozen or more files in as many shapes and sizes
as you could need. They last a while and really do a number on
cleaning heads up. .
Bob Hoover
> What tool should I use to get
> deep in there and clear out those places between the fins.
The proper tool is a pneumatically powered 'riffler' with a set of
coarse files... but since you don't have any of that stuff (...or you
wouldn't have asked the question :-) try a saber saw with a LONG,
COARSE-TOOTHED blade, such as for cutting wood. That should fairly
well on the fins. But the holes around the exhaust valve guides are
more important (seriously). Try using long drills ('air-craft
drills'). You can't use most rotary tools... as soon as they pick up
a bit of aluminum they become imbalanced and are liable to walk the
die-grinder right out of your hand, Worse-case? A set of Swiss
machinist's files and LOTS of patience. (Give the files a spritz of
WD-40 every now & then to keep them from loading up.)
---------------------------------------------------------------------------------------------------
> I know it seems anal but I am trying to blueprint the cooling design
> of my 1776cc Type 1 engine (with Webcam 163 camshaft) so that I may
> safely run a higher CR (9.2:1) while running pump (Premium) gas in
> California. I am running the late Doghouse fanshroud with all cooling
> flaps and all the other various cooling tin that everyone forgets
> about.
> ------------------------------------------------------------------------------------------------
I think you'd be wise to stick with 8.5:1 or LOWER. It's not you nor
the machine work, it's that rotten fucking FUEL they're selling us
nowadays. It may say... whatever on the pump but that doesn't mean
that's what you're getting in your tank. My bike runs 10:1 (old
CX-500) The only fuel it will run on nowadays is 100LL from the
airport. Liv & lurn.
-Bob Hoover
Geoffe Elias
tools. Am going to look into the cheapo diamond rifflers as suggested
by jtbartlett as well.
Meanwhile, while searching around, discovered the following place
which think is a brilliant idea:
http://www.techshop.ws
Too bad about the crap fuel issue though. I guess besides the fact
that watercooled engines can handle autodetonation better due to their
ability to shed waste heat better, they also can rely on a whole bunch
of other tricks like computerized engine management with knock sensors
and such.
-Geoffe Elias
'74 Super Beetle
Jan
> Too bad about the crap fuel issue though. I guess besides the fact
> that watercooled engines can handle autodetonation better due to their
> ability to shed waste heat better, they also can rely on a whole bunch
> of other tricks like computerized engine management with knock sensors
> and such.
engine management and knock sensors are also available in many
aftermarket kits, that could also be used on an aircooled VW engine.
Many people have "modernized" their VW engines this way, especially when
building turbo engines that by nature come with higher risks of
detonation damage etc.. and really need good mixture control.
Bob Hoover
> I guess besides the fact
> that watercooled engines can handle autodetonation better due to their
> ability to shed waste heat better, they also can rely on a whole bunch
> of other tricks like computerized engine management with knock sensors
> and such.
> -----------------------------------------------------------------------------------------------------------
It's not just the fact they are liquid-cooled. The foundation issue
is the use of a computer to control the process of combustion. Most
folks start acting silly when you say things like that but it's the
truth. Light the fire in ANY gasoline-fuel, spark-ignited engine and
the following 'combustion event' will take something like two
thousandths of a second REGARDLESS of your rpm. (There is a clue
buried in there. QED and all that.) The basic combustion controller
is a chip from Zilog. Pretty crude but it's cheap and has a good
track record with regard to failures. AND it runs in the megahertz
range, meaning you've got tons of time to do whatever needs doing
before the NEXT 'combustion event' comes around.
But that's just the start of it. In a modern-day vehicle you're
liable to have as many as SEVEN 'computers,' if your definition is
limited to microprcessors capable of reading instructions, doing
things and recording the results. The literal definition of a
'computer' is an MPU, an I/O controller, and some memory. The fact
you can get all that on one chip doesn't change anything. The
distinction is between 'controlling' something and controlling
something on the results of a computation. What makes it tricky is
when the computer in charge of combustion starts using INPUT from one
or more of those other computers to determine when the engine gets
another shot of fuel, how much fuel it gets and so forth.
Actually, it's rather interesting. Study of the code gives you a
keen insight as to the politics behind how all that crap -- most of
which is carcinogenic -- got into our motor vehicle fuel... then
getting you to pay a PREMIUM for such crap. Clearly, we have the best
government money can buy :-)
-Bob Hoover
P.J.Berg
Well, we have the best Gazoline money can buy...
Our politicians on the other hand you can have at a very reasonable rate. :-]
J.
--
Using Opera's revolutionary e-mail client: http://www.opera.com/mail/
j...@fake.com
the following 'combustion event' will take something like two
thousandths of a second REGARDLESS of your rpm<<<
Well, sorta. It will depend greatly upon the combustion pressure. At peak
torque the fuel is burning much more rapidly than at cruise.
>> The basic combustion controller is a chip from Zilog.<<
I think that most current automotive applications use the Freescale line
HCS12 processors. They replaced the Mot6800 Risc and Zilog series in most
cases.