VW - PERFORMANCE 5/5
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Author: Robert Collins
Some editing: Jan Vandenbrande

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				PART - 5 -

>From: rob@conexch.UUCP (Robert Collins)
Newsgroups: rec.autos,rec.autos.tech,rec.autos.sport
Subject: VW High Performance (Microview Part 5)
Keywords: zoom
Date: 22 Jul 88 05:49:37 GMT
Organization: The Consultants' Exchange, Orange County, CA.  (714) 842-6348


     In this long awaited article of VW High Performance (Microview),
I will discuss big valve heads and porting.

     Everyone has their own version of a high performance VW head.
Each company is convinced their head is the best -- the best compromise
between performance and cost.  As I mentioned in the last article,
I have noticed ulterior motives in their definition of 'best' cylinder
head.  I have found that what each company sells is directly related to
how extensive their machining facilities are, or the size of their
technical staff.  To put it another way, their way is the 'best' because
that's all they can do.

     But the real question is:  what is the 'best' way to make the VW
head high performance?

     In general, to make a head high performance is a multi fold
process which includes lightening the valve train, porting & polishing,
using larger valves, and installing a camshaft with more lift,
and/or duration.


Lightening the valve train:
     Lightening the valve train enables your motor to rev quicker and
higher, thus have more horsepower and faster throttle response.  All race
motors built at Drake Engineering either use Titanium (Ti) valves, or
lightened steel valves, and most certainly Ti valve spring retainers.
No matter how you look at it, lightening the valve train is a very expensive
process.  The process would benefit all motors from race to street, but
cost is the inhibiting factor for street cars.

     Ti valves cost over $60.00 ea., while lightened steel valves cost
~30.00 ea.  Lightened steel would probably flow better, due to the
lightening technique.  At Drake, we lightened valves by decreasing the
diameter of the valves stem between the valve guide, and valve head.
This area is where intake and exhaust gases flow around the valve.  By
decreasing the diameter, there is less of an obtrusion, and therefore
better flow.  Further lightening is obtained by machining the valve
head itself.  Machine the bottom of the valve head, to make it concave,
and the curved radius where the valve head meets the valve stem, by
decreasing the curvature radius.  The effect is better flow, and a
lighter valve.

     Further lightening is obtained by using Ti valve spring retainers.
Ti retainers cost ~15.00 ea. and are (for VW) only available for a 3-groove
keeper.  Ti retainers weigh only 2/3 of the normal steel retainers, but
due to the 3-groove keeper (which is actually better than 1-groove
keeper), can't be used for most street applications.  Nobody I know of,
including Drake, has a tool to machine 3-groove keeper grooves.  (A
3-groove keepered valve rotates better and therefore the valve lasts
longer than its 1-groove counterpart.)


Porting & Polishing:
     Traditionally, horsepower gains are in the cylinder head.  This is
why it is extremely important to give the head a massage.  This process
starts with porting & polishing (henceforth:  P&P).  There is a big
difference between a 'street' port & 'race' port.  Primarily, as with
street ports, all that needs be done is open the ports up to, and match
the gasket size.  There is no sense in porting any larger, as the gasket
will restrict the flow, and torque will suffer as a result of ports too
large.  By making the ports too big, port velocity decreases, and the
effect is to shift the power band upwards.  Since HP is related to
torque by RPM, torque will suffer by moving the power band up.  So, the
best compromise is to port-match with the gaskets.

     Occasionally at Drake, I would get a guy that wanted racing ports
for his street rod.  I would explain to him that his perceived performance
would suffer.  The cost is too high ($1200 or so), low end torque would
seem wimpy, therefore he would not be satisfied with the results.  After
much reasoning, the customer would always settle for the street ports.
In order to effectively use racing ports on the street, you also had to
use a racing cam.  Can it be done?  Yes, with much expense.

    I had such a motor built for myself.  Here was my idea:  Build a
big bottom end (1997cc).  Have the head ported with race ports, then
use our smallest racing cam.  With this configuration, my goal was
let the displacement provide the torque, and the head provide the
horsepower.  Any guestimates as to performance?  Don't know yet, as
the motor is in final assembly now, but I'll guess 170 STREETABLE hp.
For those of you familiar with the Rabbit motor, you'll know that
170hp out of a naturally aspirated 8v street motor is incredible.


Big valve heads (BVH):
     Most company's offer a high performance head for the 1.6, but only
Drake offers the BVH for the 1.8.  The reason is twofold:  To make a 1.8
BVH requires valve manufacturing facilities.  Only Drake and Techtonics
have such facilities.  Manley is the only manufacturer of valve 'blanks'
suitable for machining valves for the 1.8.  And Techtonics refuses to
buy Manley valves, because of some bad business deal many years ago.
In short, Drake is the only 1.8L BVH maker.  Unfortunately, the honesty
stops here.

     As I mentioned in my last article, the 'best head' you could put on your
car is determined by what a particular company has to offer.  In the case
of the 1.8L BVH, more than likely, you will be told that the 1.8 "doesn't
respond to a BVH like the 1.6, and therefore isn't cost effective."  Even
Techtonics will tell you that.  If you are able to read through the lines,
and know the insides of each company, what you really hear is that they
either don't have the technical skill to make it work, or (as Techtonics)
won't buy the parts from the only available source.  But the real question
is, does the 1.8 need a BVH, and is it true that it doesn't 'respond' in
the same manner as the 1.6?  The answer is a little complex, and requires
some knowledge of the 1.6L motor.

     At Drake, we had 'Stage kits.'  These kits were incremental steps
designed to give the best hp/$.  We dyno tested all the kits and every
conceivable combination of parts.  The results surprised the public, and
infuriated our competition.  To the publics surprise, they found that
the industry 'staple' parts did little or nothing to enhance their
performance.  For example, a larger throttle body didn't produce a
single hp gain until a big valve head was added.  Similarly, the G-cam
didn't do much of anything for hp, just added a reasonable amount of
low-end torque (seat of the pants feeling).  The culmination of this
testing were stage kits that gave you the parts in order of their usefulness.
Stock:  74hp 1.6L motor
Stage 1:  Exhaust & recurved distributor        = 91hp
Stage 1+:  Cam & throttle body                  = 97hp
Stage 2:  Big valve head, w/cam & throttle body = 121hp
Stage 3:  Build the bottom end to 1848cc        = 130hp.

     So as you can see, the big valve gave a tremendous (30) hp advantage.
How does the 1.8L motor respond?

Stock:  90hp 1.8L motor  ('83-'84 GTI, not GOLF GTI)
Stage 1:  Exhaust & Recurved distributor        = 105hp
Stage 2:  Cam & throttle body                   = 121hp
Stage 3:  Big valve head                        = 130hp

    Consequently, it can be said that the 1.8L motor doesn't 'respond' as
well to the big valve head as the 1.6L motor, since the 1.6 yields 24hp
over the cam kit & exhaust, but the 1.8L motor only yields 9hp.  But why?
The big difference is valve size, and the ratio of increased valve area
from the 1.6 to 1.8L heads.  The 1.6L head comes stock with 36mm intake and
32mm exhaust valves.  They can be increased to 40.5mm/34mm valves.  The
1.8L head however, has 40/33 valves from the factory, and can only be
increased to 42/35mm valves.  Thus, the ratio of increased valve area is
much smaller, therefore the expected hp gains are much smaller.

     So, what about this business of selling BVHeads and what is the
'hot' setup right now?  For the 1.6L heads, most people are buying heads
from a company called "OVERLAND PARTS."  Overland is able to get 1.8L
heads machined to fit the 1.6L block.  This is by far the cheapest way
to get a BVH for your 1.6L motor.  It comes with 40/33mm valves, and only
costs ~500.00.  It doesn't have the ports polished though, and this is
a major drawback.  By the time the head is disassembled, polished, and
reassembled, you have spent close to the $900.00 Drake charges.  Which
would I buy?  If money was no object:  Buy the Overland head, and send
it to Drake for 42/35mm valves, including porting & polishing.  You will
have the BIGGEST valve head for the 1.6L motor around.  If money was an
object however, I wouldn't buy the Overland head at all, but simply have
Drake build me the head.  Why Drake, and not Techtonics?  Lately Techtonics
has been buying the Overland heads, thus Drake is about the only company
that still even builds their own BVH's.  Finally, as one last convincing
memo:  one of our competitors (name purposely omitted) used to call us
the 'butchers of headwork.'  It just so happens that he built the motor
for the guy who painted my car.  In a swinging deal with him, I sold
him the 1997cc motor I mentioned above.  The buyer looked at the headwork
(and comparing to his current head) remarked that he had never seen a
head so cleanly done, so perfect.  He called our competitor to come over
and give his opinion, and the competitor said he 'had never seen a head
so beautiful in his life...he would buy it in a heartbeat.'  It's funny,
there was nothing special about that head...ALL Drake heads are built
just like that one.


To make a big valve head:
     To make a 1.6L big valve head, most people use the Manley valves.
These valves are .100" longer than stock, thus the base circle of the cam
is smaller by .100".  (See illustration below).  For the most part, this
is an easy process.  Nothing special need be done.  Just call your favorite
cam grinder, and tell them you need a XXX cam on 1.400" base circle with
110 degree lobe centers (110 for f/i; 108 for carb; 113 for turbo).
You will also need valve seats, and other hardware.  Still, nothing
complicated.


         /--\
        /    \
       /------\
      /        \
     |<-------->|
     |  base    |
      \  circle/
        \_____/



     The 83-84 1.8L head is similarly simple, but since the valves are
specially made by Drake, the valve stem length is identical to stock, and
therefore the cam base circle can remain stock sized as well.

     The hydraulic head is the real nightmare.  In this head, MUCH has
changed.  The valves are shorter.  The cam base circle is smaller.  The
distance between the cam bearing bore centers and cam follower holding
tray is much smaller, therefore requiring clearance grinding for almost
any (true) high performance cam.  The valve guide protrudes much farther
into the ports.  And the valve spring depth is deeper (though the valve
springs are the same size).  All this is because of the difference
between hydraulic and mechanical lifters.   In order to make a big valve
head from this head, some serious decisions must be made:
1) Do you keep the hydraulic lifters, or switch back to mechanical
2) Valve length (dependant of type of lifters)
3) Valve guide length (depends on type of lifters)
When we designed the hydraulic BVH we made this, and only this assumption:
1) This is a high performance head.
Therefore, who cares about hydraulic lifters and the convenience of never
having to adjust the valves.  Furthermore, there are performance penalties
for using the hydraulic lifters:  a substantial weight penalty.  And for
all high performance applications, a major quest is to lighten the valve
train.  Since the decision was made scrap the hydraulic lifters, then
this cleared the way for other performance penalties:
1) Cam lift size.  This is because there are no billets available for the
   hydraulic head, and the maximum variance of lift from stock (dictated
   by the hydraulic lifters) is +-2.0mm.
2) Valve guide protuberance.  Make spacers to take up the slack, thus
   still using street valve guides (longer, thus longer lasting than
   racing).
3) Valve spring installed height.  Thanks to the spacers made for the
   valve guide boss, the valve springs can sit at their optimum height
   for lift before coil bind.

     In retrospect, the design of the hydraulic BVH was a very good design.
And after witnessing the immense design process this head required, I am not
surprised by the fact that no other company's offer a BVH for this motor.
Instead, they'll simply tell you that it isn't needed.  But I hope by now
you can read through the lines.

     Finally, since the hydraulic head requires so much more machining,
the cost is obviously higher.  While I was at the helm at Drake, I offered
both heads (hydraulic and mechanical) at the same price -- as an introductory
offer to the BVH -- though the cost differential is over $100.00.

     In conclusion, the best performance gain from your car isn't in the
bottom end, but the cylinder head.  By increasing the displacement, you
will gain a moderate amount of hp, but by making a BVH, you can gain vast
amounts of hp -- dictated by the $_amount_$ you want to spend.  If I had
my choice of head work, or bottom end work, I would choose the head work
every time.  Remember, your bottom end will (generally) last much longer
than you cylinder head any ways, and the increased displacement/hp gained
is far disproportionate to the increased performance from a BVH.

Next issue:  Camshafts.


-- 
"Worship the Lord your God, and serve him only."  Mat. 4:10
Robert Collins                 UUCP:  ucbvax!ucivax!icnvax!conexch!rob
HOMENET:  (714) 995-7344       UUCP:  uunet!ccicpg!turnkey!conexch!rob
WORKNET:  (714) 229-0284


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