perf-list-digest Sunday, July 19 1998 Volume 01 : Number 034



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Ford Truck Enthusiasts - Performance
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In this issue:

FTE Perf - gary's stuff... my opinion
FTE Perf - Valve seats, SS Valves, Port Finish

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Date: Sat, 18 Jul 1998 22:15:10 -0700
From: "Darryl A. Regan"
Subject: FTE Perf - gary's stuff... my opinion

From: "Darryl A. Regan"
To: perf-list ford-trucks.com
Date: Sat, 18 Jul 1998 21:44:23 -0700
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Subject: Re: FTE Perf - Gary's opinions!
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From: "Chris Samuel"
To: "Perf-List"
Subject: FTE Perf - Gary's opinions!
Date sent: Sat, 18 Jul 1998 18:07:16 -0700
Send reply to: perf-list ford-trucks.com




>
> The weight difference you mention is not just 150 LB. it totals much more!
> You forget to mention, or perhaps you don't know, that the extra weight of
> the 385 series engines pushes the limit of the Dana 44 front axil should you
> ever catch air, I play hard and I have had multiple feet of the stuff (and a
> creek)under all 4 corners simultaneously. This combined with excess power
> creates a mandatory front Dana 60 or 70 swap, more weight; and the D60/70
> should be fully gusset'd; More $$$$, More Weight!


Just wondering why we aren't hearing about tons of breakage from the hardcore wheelers
who have a few extra hundred pounds of winch and bumper hanging over the front of their
trucks. Also show me where it cost more to build a 460 than a 400. I cant find this info.
Kind of like the guys saying it would cost so much moe to build a 351C than a 351W. I
have some pretty good catalogs that say otherwise. Oh yeah everything I read says the 460 is about 145 pounds heavier than the 400.


dar6 jps.net
78 Bronco Ranger XLT (460 powered)


dar6 jps.net
78 Bronco Ranger XLT (460 powered)
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Date: Sat, 18 Jul 1998 23:24:26 -0700
From: "Chris Samuel"
Subject: FTE Perf - Valve seats, SS Valves, Port Finish

- ->How does the 30 degree seat measure up to 45 for normal highway driving?

- ->George Miller

The 30º seat will work well on most engines right on up into the 6.5k RPM
range. The reason for this is that the Curtain Area is greater sooner in the
valve event timing. For most streetable cams the amount of time that the
valve spends at 1/3 lift is greater then the time at full lift. The most
critical time is the last or closing side of the event. The closing side is
critical because the air column has reached its maximum velocity, so if you
can improve the flow on this side you will make more power in any engine and
at any RPM (ok, almost any).
The 30º seat will give away some peak air flow to the 45º seat, however from
what I have seen and read it would not matter to most people on or off the
track as the overall flow increase will offset the top end loss. So, unless
you are living and dying by the last horse, particularly in a stock
production head the 30º seat is the way to go.
Down sidez:
The 30º seat provides less self centering action, and tends to be slightly
less self cleaning. Depending on the way (other angles)that the seats are
ground may tend to cause the valve to run hotter. So the 30º seat has a
small risk attached to it, the risk under 6k RPM in an application that is
running appropriate air filter is low. The use of this angle in "Heavy Duty"
or "Severe Duty" applications may not be the way to go for the above
reasons.

The latest thinking on seat prep is not to grind a radius after the blend
into the valve pocket but to run a series of descending angles. The
reasoning is that Air can't see these small angles at speed but it does see
the radius and so the radius develops a greater boundary layer and
turbulence. The old 3 angle valve job has turned into a 5 to 8 angle (or
more) affair on high output engines. In a modern shop all of these angles
are machined and not ground, so it is not that much more expensive then the
old 3 angle. A lot of people are still paying top dollar for the radius
work, oh-well you got to have what you got to have.

Reason to run Stainless Steel Valves?
Stainless offers a higher strength potential at elevated temperatures. If
your application will introduce this type of condition, like starting the
engine, you MAY benefit from SS Valves.
Why? Because the SS Valve is stronger less metal can be used to give the
same or often greater strength when compared to the stock valve.
If you reduce the weight of the valve you can run a lighter spring; lighter
spring gives you power. Lighter spring and valve allows a higher
acceleration rate of the valve and more importantly a higher closing rate,
this allows the valve to get farther open sooner, and be held there longer
in a given duration, of course that would be a custom camshaft.
Running a SS Valve and optimizing nothing else can extend the RPM's before
Valve Float destroys something, and that can give some power. But if you are
going to order a camshaft telling them that you are running a "Super Trick
Lightweight Valve" may allow them to change the springs and Camshaft giving
you a more optimized Valve-train and therefore more power.

On the street SS Valves in a relatively stock application may yield nothing
in any measurable terms. But... If "I" am building a "Hi-Pro" engine and
starting with used components like heads, "I" replace the valves, ETC. just
for safeties-sake, all metal fatigues and "I" find the risk of 25 year old
valves or even 2 year old valves to be unacceptable. That's my problem
though...

Intake and Port Surface Finish.
I have watched this thread with interest. Here is what I have learned
working with max-effort engines, the principals and applications of them
directly apply to street engines.
Polishing is a waste of time!
The Manifold and Runner need to be smooth in the sense that the contours
need to be. But the actual surfaces want to be rougher then most people
would like to believe. Most of the super smooth surfaces are there not
because they make power but because 'you' the customer would feel cheated if
they were not!
The A/F mixture is not mixed on the Plenum, the mixing is done in the Carb,
or at the Injector. Fuel is placed in the air stream in the form of tiny
droplets. The size of these droplets is directly proportional to the power
made: smaller is better. As the droplets move through the manifolding they
bump into each other making bigger droplets; or they bump into the walls of
the manifold and stick there. The bigger the droplet the more likely it is
to bump a wall and the more fuel falls out of suspension. This happens with
the glorified EFI systems even worse then Carbs because the droplets start
out bigger! Anywayz quite soon you have a river of fuel, yes literally,
running back and forth in the manifold.
As you can see the last thing that you would want is "Mixing" happening
anywhere in the manifold. What you want is a nice smooth orderly flow to
keep the fuel mixed in the air. (note: sometimes raising the Carb or T/body
will help in sorting out the flow and yield a dramatic increase in power) So
the trick is to get that fuel back up into the air stream. If the manifold
is a poor design or designed for emissions sometimes the only way to do this
is to heat the manifold with the exhaust and boil the fuel back into the air
stream. A good manifold design may need this heat feature while the engine
is cold but not after that point.
When air moves through a tube it is not all moving at the same speed. There
is a layer that is in direct contact with the wall that may not be moving at
all (called the Boundary Layer) while the air in the center is well above
the average velocity creating a speed gradient between the two extremes
(AFAIK all gasses and liquids act this way). As the speed of the air through
the tube increases the thickness of the Boundary Layer increases; this is
the reason that high RPM manifolds have bigger runners. If you increase the
speed enough the Boundary Layer will be the same thickness as the diameter
of the port and you will "stall the port".
If the wall is mirror smooth the air will simply push the liquid fuel and
the Boundary Layer will still be there but on top of the fuel; but if the
walls are rough there is a change that happens in the Boundary Layer; it
lifts off the wall taking the fuel with it. Presto Fuel back in suspension.
Real big drops perhaps but a big drop is better then a river any day! This
"turbulence" is a good thing!) not too much mind just the right amount. With
the turbulence you can still stall the port, and it may happen sooner then
otherwise. An interesting thing happens when the port stalls, the fuel falls
out of suspension and the engine goez lean and meltage happens shortly there
after.
I know that the conclusion reached logically that the rougher wall texture
the more the increase in the Boundary Layer thickness and reduces the CFM
capability, and the sooner it happens speed wise appears to be all bad.
Most of us will never demand enough air to come close to stalling the port.
The apparent and popular conclusion is that you should have the smoothest
port as possible to reduce it. If you have time or money you can achieve a
mirror everywhere. You might measure an increase in CFM but how much is from
polishing and how much is from the enlarging and contour smoothing, like
Extrude Honing. For example smoothing the bumps in the 460 heads is worth
around 20 or so HP, but polishing the port makes an inconsequential
difference.
So what is the ideal surface finish?
Depends on the application but vary generally the finish produced by the
first tool used in actual porting is correct: the Carbide Burr. Don't grind
or sand after hogging out the ports, just go back over them and smooth them
with the Burr and your done; unless your going to sell it, then polish them
ports!
The Exhaust ports do however like to be real smooth so finish them off with
a Mounted Point, you don't need to sand or polish these ether unless your
going to sell them.
Here is another general rule don't sweat the bottoms of the ports, most
dramatic improvements will be found in the sides and tops of the ports;
particularly Ford exhaust ports. All of them! and watch out for water!
You can guess what I am going to say about the Chambers… Nope you don’t need
to polish these ether; just smooth them out with a Mounted Point. The poor
quality of gasoline sold in this country will put a layer of carbon on a
polished surface just as fast as a surface that has only smoothed, another
popular myth blown away! Sorry.

The above is a much simplified outline based several documents in my
possession:

Several articles, by David Vizard
"4 Stroke Performance Tuning", by Sorry I can no longer read it.(what a
name)
"Air Flow through Engines", By Superflow Corp.
"Impact of Accelerative Forces on Performance in Race Engines with Wet-Fuel
Manifolds", By Andrew L. Randolph and Alba L. Colon
"Internal Combustion Engine Fundamentals", By John B. Heywood
And a bunch more; Also a bunch of my experiences, both bad and good!

CS.


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