I have used epoxy. I've used JB Weld and it is generally thought to
be superior as far as stiction goes, but it is so runny that you have
to build a dam to keep it in and then grind all of that away. A
product that is easier is Moroso A & B. It comes in two bars about
like big Snickers bars. It is made expressly for this purpose. It
works fine but you must be very careful to mix it thoroughly before
use. I have never tried it in an exhaust port but only in intake
ports. I've never had a failure, but the danger is always there, and
I no longer use it. I've found ways to make the TR4 head flow just as
well without it.
One of the most interesting experiments was trying to make a "high
velocity" port like they use on high rpm motorcycle engines. I
theorized that the best place to restrict the flow was right at the
downturn of the port. I built up the radius until there was only
about 60% of the port cross sectional area remaining. Then we took
the car to a chassis dyno and ran it with a head with epoxy and a
head without.
Common sense told me that we would lose hp, but I've seen the dyno
curves for hot bikes and they showed higher hp so I was really
curious about it. Plus I was out of ideas at the time. We found that
this experiment lost us 8 hp.
I later tumbled to the fact that the cycle guys experience gains
above 8000 rpm, not below.
At 01:34 PM 11/11/2007, you wrote:
>Has anyone had success using an epoxy to change the shape of an intake
>or exhaust port or is welding the only way to go?
>
>Thanks,
>
>Greg
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uncle jack
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