[DeTomaso] Stack Filters& cool air
JDeRyke at aol.com
JDeRyke at aol.com
Sat Jul 11 15:01:04 EDT 2009
In a message dated 7/10/09 5:33:41 PM, wdemelo at cogeco.ca writes:
snip.....
> I'll remove the quarter glass to introduce cool air. The plenum will
> extend rearward by about 4" so it is under the decklid and I'll use foam under
> the deck to create a seal against the plenum.
>
You're going to lots of trouble to get a pure-racing look in a mostly
street car, so you really need to choose between -A- the engine wears out its
rings rapidly due to inadequate air filtration but looks 'right', or -B- the
'look' is not what Euro race cars of the day had but you won't need to rebore
the block and replace rings & pistons every few thousand miles or so.
I think rear quarter glass removal will do nothing except remove 6 lbs of
weight. Airflow below 140 mph is OUTWARD thru the glass openings due to high
velocity air from under the car coming up & out; outside air will not bend
inward against that flow at lower speeds, even with big scoops. The only
known ways to get cool(er) air to the carbs is to fabricate a rear-facing
carb-box like Shelby did with the Cobras, build a roof-top air scoop, or take air
in from far away from the carbs- near the tail lights- like Ferrari did with
the Boxer.
Second, one of the neat things about Webers is the extremely strong
pulsations in individual-runner intakes. I assume your 'plenum' will interconnect
two or more intakes together but I'm unsure of what your design will be with
this device. It may change normally fussy Weber tuning to some sort of unk
own so you- and your dyno man- may be on your own here.
My suggestion is to stay far away from any kind of foam near Weber carbs;
the reverse intake pulsations carry fuel back up to the foam which soaks it
up like a sponge. Any backfire (very easy with choke-less Webers during
starting & warm-up) and they burst into flame. The main venturis & protruding
aux. venturis are zinc and melt very quickly in a flame. The molten zinc then
flows down past open valves and sets up again as a metal lump on top of one
or more pistons. Which impact the head and crack when you hit the starter.
Been there, done that and it ain't fun..... Incidently, ANYONE running Webers
needs to carry at least a good 2-1/2 lb Halon fire extinguisher; better is
an on-board fire suppression system. And a cell phone with a good tow company
on speed-dial. Even old well-soaked paper filters can catch fire, as I
found. This is way-too exciting in the middle of a six-lane freeway....
Your website photo showed K & N filters which work fine if you follow K&N's
instructions religiously. For instance, use their oil on their filters at
their suggested intervals, and do NOT use soap & water to clean them in place
of K&N's expensive cleaner. Soapy water will swell the fibers in the
filters, and your nice clean air filters will suddenly not pass rated amounts of
air, losing mucho horsepower for no obvious reason.
Welcome to the wonderful world of Weber carbs! They're great when they work
right. Otherwise, its like being married to a beautiful woman with
permanent PMS and a concealed-weapon permit....Good luck - J Deryke
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