VW - PERFORMANCE #4/5
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Author: Robert Collins
Some editing: Jan Vandenbrande

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Disclaimer by the editor (& presumably the author):

These articles should be regarded as opinions and not fact.
If any product's name or company is mentioned, no connotation should be 
taken for its actual quality, value or use.
There is NO guarantee any of this information is correct.
Neither the authors, editors, or those who maintain these archives take
any responsibility for the consequences that may result from applying
any of the ideas presented within these articles.
Severe damage, injury or loss of life may result from applying the ideas 
presented.
Furthermore, before implementing any of the ideas, check whether such
modifications are allowed in your state, province or country.

All articles may be distributed freely and copied (unless otherwise stated)
as long as the original authors or origine are identified if available.

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			PART - 4 -

From: rob@conexch.UUCP (Robert Collins)
Subject: VW High Performance (Microview Part 4)
Keywords: zoom
Date: 9 May 88 03:20:10 GMT
Organization: The Consultants' Exchange, Orange County, CA.  (714) 842-6348


In this installment of VW High Performance (Microview Part 4), I
will discuss cylinder heads in depth.  What you can do to a
cylinder head, and what effect it has on performance.  

It has been said:  "Speed costs money...how fast can you afford 
to go?"

This is quite true of cylinder head modifications.  Many companies
offer high performance cylinder heads that vary in their state of
tune.  Some believe that porting and polishing is adequate, while
others also put bigger valves in the head.  The bottom line is
salesmanship.  They will tell you whatever they have to in order
to get a sale.  One prevailing truth is that their way is the
best.  

In the following pages, I will discuss the various cylinder head
components, and what effect the modifications have to each class
of cylinder head.  Keep in mind that I will mention pros and 
cons for most subjects.  The cons are usually related to 
salesmanship -- where you will be told that that company doesn't
do it that way because:  
1) it isn't needed
2) the performance gain isn't worth it
Whatever their reason, the bottom line is sales - and that is their
ulterior motive.

So starting from the bottom up, here are the components:


Combustion chamber:  
To polish, or not to polish.  There are good reasons to polish the
chamber, and mediocre reasons not to.  The reason to polish is 
primarily to blend in new valve seats into the combustion chamber.
Another reason is to eliminate hot spots in the chamber caused
by sharp angles left from the casting process.  Hot spots cause
predetonation, also known as pinging.  Another reason to polish
is that it simply looks good.  And finally, polishing the chamber is
the easiest way to adjust for compression ratio differences from 
cylinder to cylinder.

Typically, each cylinder has a different compression ratio.  This
ratio will vary a couple of tenths from the mean.  In a racing
application, most builders will compensate until each cylinder
has the same compression ratio.  This is done by machining each
combustion chamber until the desired volume is obtained.

For the curious, compression ratio is defined as:
The ratio of volume before and after compression.
And therefore is calculated by this formula:

Let:
S  = crankshaft stroke in mm.
B  = cylinder bore in mm.
D  = deflector:  CC's below the block deck at TDC (>0 if piston is below
                 the deck, or <0 if piston is above the deck)
GB = Head gasket bore
GT = Head gasket thickness while in use (compressed by cylinder head
                 properly torqued to block)
CC = CC's in the combustion chamber of the cylinder head
VB = Volume before compression
VA = Volume after compression
CR = Compression Ratio
Pi = Pi (3.14 etc)


VB == (Pi x ((B/2)^2) x S) + (Pi x ((GB/2)^2) x GT) + D + CC
VA == (Pi x ((GB/2)^2) x GT) + D + CC
CR == VB/VA


Opponents of polishing will tell you that polishing will actually
cause hot spots in the chamber.  This isn't true.  They merely 
tell you anything they can to convince you NOT to buy from 
someone else.  Their real reason might be to save money - which
makes their price look better.


Valve seats:
The valve seat is the sealing surface in the combustion chamber
that meets the valve.  It's purpose is to seal the combustion
chamber during combustion; and to dissipate heat out of the valves
into the head.  The factory uses steel seats which last a long time.
For high performance street heads, Drake recommends a high-nickel
alloy.  For racing, a brass alloy is used.  The main difference
between street, high performance, and racing is wear and weight.
It's hard to imagine weight being a factor, but to a racer, every
gram counts.  A high-nickel alloy lasts a long time, and dissipates
heat very well.  Brass is lighter, but doesn't last very long.



Valves:
The most popular valves on the aftermarket are Manley.  Manley
makes stainless steel valves.  Unfortunately, they only make
valves for the 1.6L heads.  40.5mm intake, and 34mm exhaust
valves are what they make.  Since Manley doesn't make valves for
the 1.8L head, they must be custom made.  This explains why Drake
Engineering is the ONLY tuner (I know of) that sells bigger valves
for the 1.8L head -- they are the only one's that have valve making
capabilities.

In the 1.6L head, the possible combinations are:
40.5/34 or 40.5/35.  For the same aforementioned reason, Drake is the
only tuner offering 35mm valves for the 1.6L head.  Drake sells
these valves for SuperVee motors, and selling for $35.00/ea.+ they
aren't recommended for the street.

The 1.8L head comes with 40/33 valves from the factory.  So, typically
you will be told it doesn't need bigger valves; or the head doesn't
yield higher performance with bigger valves.  This isn't true at
all -- I have a big valve 1.8L head -- it responds incredibly well.
I always felt their ulterior motive for telling these stories is
because they don't have valve manufacturing facilities, and therefore
would have to buy from Drake.  Who loses?  The public of course.


Valve guides:
The valve guide does just that.  It guides the valve from the cam
housing to the combustion chamber.  I couldn't tell you what alloy
the factory uses, or what competitors use.  But Drake uses a bronze-
silicon alloy.  This alloy is self-lubricating and lasts a long 
time.

Valve guides come in two sizes:  long and short.  The long guides
are recommended for street use, as they will last longer.  Short
guides are used strictly for racing - to save weight.  I realize
it's a couple 10 or so grams, but every bit helps.


Valve stem seals:
Teflon valve stem seals (PC Seals) are the most popular seals on
the market.  Everybody uses them except the factory.  The factory
seals are junk.  In fact, there was a factory recall because of
valve seal integrity.  PC (Perfect Circle) seals are easy to change,
but must be done with a couple special tools.

Teflon lasts quite a long time, and gives the best seal protection
before wearing out.


Valve springs:
I love this subject.  I love it because Drake has the best valve
springs out on the market, and everybody knows it.  In fact,
everybody buys their springs from Drake:  Autotech, Techtonics,
ABT, Callaway, you name it.  The main reason Drake springs are
the best is because:
1) They are made from Chrome-silicon (keeps spring pressure the longest)
2) Rev past 9000 rpm's.
3) Accommodate stock (.370") to .500"+ lifts without coil bind.
NO other spring on the market can match this performance claim.

Drake has the springs specially made to their blueprint, and has
sold 1000's of sets over the past 10 years.  

Stock springs float past 7500 rpms, and can accommodate about .440"
lift before coil bind.  VW Motorsport springs are similar to stock,
but are 30% stiffer.  Therefore can rev to 8000 rpms.  Racing
valve springs are much different.  This is because racing valves 
are much longer than street valves -- typically .500" longer.
Because of the longer length, different springs are required.  


Spring retainers:
Valve spring retainers are typically made of steel.  But Drake
also markets titanium (Ti) valve spring retainers.  For street use,
steel is not only adequate, but recommended.  

The Ti retainers cost over $15.00/ea. and are only made for 3-groove
keepers.  For the latter reason alone, they can't be used for the
average high performance head.  All 1.6L heads and big valve 1.8L
heads use a 1-groove keeper; and the two retainers aren't interchangeable.  Ti has its advantages though -- 1/3 lighter than the steel
retainers.  The weight criteria is again a major factor for racing
use.


Cam followers:
There are three types of cam followers to choose from:
1) The stock 35mm cam follower
2) 35mm racing
3) 37mm racing

The stock followers sit on top of the valve, and allow valve adjusting
via an adjusting shim that sits on top of the follower.  This cam
follower is adequate for cam lifts up to ~.475".  Lifts higher than
.475" open the valves too fast and can (and do) throw the shim out
of its position.  This causes terminal damage to the cylinder head.
I have seen this happen.  It happened to a guy that just wouldn't
listen.  He wanted a racing cam for the street, but wasn't convinced
that he couldn't use the stock cam followers.  He sent the head 
to Drake in pieces...wanted to know if we could repair it.  NO we
couldn't.

The 35mm racing followers are used for most applications above .475".
These followers, as all true racing followers have no provisions
for valve adjusting.  The only way to adjust the valves is to machine
the valve stem, or by machining lash caps that get placed right on 
top of the valve stem.  

37mm cam followers are used for extra high lift cams:  .500" and
above.  The head must have the cam follower bores opened up to
37mm to accommodate these followers.  As far as I know, Drake is
the only company that sells these followers and machines the heads
on a regular basis (though Bertiles - in Chicago - certainly
has the capability, and might sell them as well).


Cam Billets vs. regrinds:
90% of all aftermarket cams are ground on the same US made billet.
It is made by CWC Textron for Engine Power Components (EPC).  It
is distinguished by its dark - almost black - color, and the letters
EPC in the casting.  APS is the only retailer I know of that imports
the German-VW billet.

The EPC billet also has two flavors.  The standard billet that
everybody gets, and one made specially for Drake.  The Drake version
was initiated at my request - due to the failure rate of the ordinary
billet.  The ordinary billet would sometimes "go flat" on about 5%
of the cars.  We noticed this problem years ago, and most users
had CASTROL GTX in common.  It turned out that Castol GTX is missing
Zinc-disulphide -- a chemical needed to protect the integrity of
this billet.  (Valvoline Racing has it.)  Thus most failures were
related to Castrol.  So, I knew EPC also made a Rabbit Diesel
billet, and they claimed no failures at all.  So with much pressure,
I persuaded EPC to make the diesel quality billet, for the Gasoline
powered Rabbit motor.  The result of this effort came into fruition
right as I was leaving Drake. 

The German billet is unmistakably the best billet -- but it's 
expensive to import.  It is compatible with all oil types (even
Castrol GTX).  

Regrinds are perfectly ok, so long as they are heat treated before
installed.  Heat treating hardens the surface to, or beyond factory
specifications.  By virtue of regrinding however, the base circle
of the cam is reduced, and therefore longer valves are needed, or
lash caps are required.  Most people use lash caps, unless switching
to a big valve head.  (The Manley valves are .100" longer than stock 
-- the precise reduction in base circle size for most cam regrinds.)


NEXT ISSUE: 
In the next issue I will cover porting & polishing and big valve
heads.


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