[Fot] Head modifications

[Jack W. Drews]

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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