Re: [T3] Heat gauge (head affect)

["Martinez, Leon" <martinezl@ftscpac.navy.mil>]

(Finally stopped lurking, just for now)

Neil,

The question is what do you wish to see and at what speed ? Want to avoid 
cracking or damaging stock heads ? Just slow down, do not drive like I do.

FROM THE TOP OF MY HEAD....

I have had much experience with the temp gauges with different brand heads.
I drive my car about 3000 miles a month, so far, it has been 6 months
without a 
major mishap (always cracking, melting or falling apart heads). I bought my 
gauges from VDO off the Bugpack or EMPI . Jim is right some folks have these

for bragging rights or do not write data down to see if what is happening 
with the heads, thus cause confusion. I have found that the kind of heads
(German, Spanish, Brazilian, American or Mexican , different valve area
design, casting,
and metal alloy, I have had all), changes what the gauges will read, also 
your fuel mixture will change the meter reading. What I am getting to is 
that what the meter will read as "normal" operating temps is up to what your

engine parts are, modifications and settings, if your engine is EFI or
Carbed etc...
Well what I am saying is that you must get used to your temp readings at
what 
you determine as midpoint or normal operating temps.

I will give you an example :
My engine EFI 1600 cc stock.
At 75 mph flat hwy in San Diego California for 1 hr
All temps are in F .


- German VW head (good) 370 degrees goes higher as road grade goes up, top
  temp seen 400 degrees at 70 mph , good hwy grade, (heads cracked after
doing
  this daily.

- Spanish AMC head (junk) 370 degrees temp goes higher as road grade goes
up, top
  temp seen 450 degrees at 70 mph, good HWY grade, (the valve seats on this
head
  melted into the head after this daily use, seen other melted examples of
this brand
  at my local machine shop).

- Brazilian Autolinea (Empi, Bugpack, CB and most Aftermarket performance
heads)
  (1/2 reach is junk) 400 degrees temp goes higher as road grade goes up,
top
  temp seen 450 degrees at 70 mph, good HWY grade, (the heads cracked around
the
  sparkplug area with 1/2 reach after this daily use, some other heads found
to be 
  machined crooked at the plug area and this aggravates the problem). I have
bought 
  6 heads in 2 years , pile decorates the corner of my garage.

- American Mofoco (Machining is crap, at least what they gave me after I
returned it).
  325 degrees temp (cooler) but goes WAY higher as road grade goes up, top 
  temp seen 550 degrees at 70 mph, good HWY grade, (one head dropped both 
  valve seats in one cylinder after this daily use), the head seemed to have
been
  machined very badly , this was visible from external inspection. 2 heads
bought
  one head still in use on cyl #1 and #2 . Suspect that higher temps at 
  high speed is due to exhaust valve area cooling is limited because 
  the lack of flowthrough of the casting design.

- Mexican Genuine VW head bought at Mexican Dealership (are available in USA
  from different suppliers). 250 degrees temp (MUCH cooler) and stays cooler

  at higher speeds than the others. Temps stays 25 degrees below the meter's

  midpoint of 350 degrees even at 90 mph for 15 minutes on varied grades. 
  Never seen any reading above 350. Cooler temps seem to be due to the metal

  alloy and the flowthrough design of the air around the exhaust valves and 
  thicker valve stem areas.

  See what I mean ? All readings were taken from same engine in a couple of
years
  with no other engine modifications. Readings also depend on where you
mount the 
  sensor or sensors. No one person has a standard sensor location, not to
mention 
  engine types, sizes etc... See Jim's muddying comment ? This is where I
placed
  my two sensors, (one on each head), at the top foreward head bolt of # 3
and # 1
  head compustion chambers. I did not choose to install the sensors on the
standard
  location as per the instructions because the location makes it difficult
replace 
  the Sparkplug and may require head machining in order for the sensor to
lay flat
  on the surface. This location , at least to me is not the hottest area
that will
  not give a reading to prevent head damage (intake runners run near this
area).
  I chose the hotter area nearest the exhaust that never cools off but
increases 
  with engine load, near the exhaust valve guide area. This location and the

  Valve guide input I received from the VW aircraft experimenters that beat
the
  engines up more than the VW's on wheels.

   I hope my info has helped.

LEON MARTINEZ

SAN DIEGO AND TIJUANA

69 SQUARE
73 FASTY
67 FASTY












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