perf-list-digest Wednesday, July 22 1998 Volume 01 : Number 037



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Ford Truck Enthusiasts - Performance
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In this issue:

FTE Perf - Re: LAMINAR FLOW
Re: FTE Perf - Re: LAMINAR FLOW
FTE Perf - Fellow Ford fan has passed on.
FTE Perf - building a 400
FTE Perf - Air Friction?

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Date: Tue, 21 Jul 1998 08:24:55 -0400
From: "Neal B. Forbes"
Subject: FTE Perf - Re: LAMINAR FLOW

Hello motorheads! As a pilot, I know something about laminar flow over wing
surfaces and I gotta think that the principle of physics is universal.
Laminar flow MEANS unimpeded parallel air passage over a surface. That
surface MUST be as slick as possible because impediments to that smooth
passage of air cause turbulence which (in the case of a wing) spoils the
lift. On a laminar flow wing, even the teeny bit of bumpiness caused by
frost makes takeoff a "no-go" condition until it melts. As Steve correctly
points out, rough surfaces do create eddies and may help to mix air and
fuel, but eddies do not smooth the flow--they ruin it. This is why porting
does so much good--it speeds up the flow by "straightening it out".
I have a 292 Yblock and am installing a 4bbl. When I was refinishing
the manifold, I noticed that the floor of the plenum right below the carb
throats was ribbed! They ended when the runners diverged from the plenum
chamber. Turbulence here seems like a good idea--mixes the charge better.
I also noted that the runners are rectangular and of constant dimension. I
remember an Edelbrock torker that I had on a MoPar 318 once and its runners
choked down as they approached the head. This is the "Venturi effect" which
speeds up the flow as the runner chokes down, ramming the air into the head.
Power is improved because the intake vacuum is assisted-- more charge moves
in with less work. The YBlock's reputation for being a poor breather seems
deserved. (But I can smoke 'em pretty good on antique night down at the
SuperK and nothing sounds like my YBlock growl!)
I guess I don't know why anyone would WANT to wreck the air flow near
their heads by intentionally roughing up the internals of their intake
runners.
Neal Forbes 54 F100 (Hot Heap)


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Date: Tue, 21 Jul 1998 06:38:45 -0700
From: "George"
Subject: Re: FTE Perf - Re: LAMINAR FLOW

What about the friction differences of dry and wet flow within a contained
area (intake runner) abruptly ending (the combustion chamber)? As Chris
Samuel pointed out, it isn't a 'non-stop' flow, it stops every time a valve
closes. Aren't we back to the desirability of some surface distortion
creating turbulence to assist the mixture in staying in suspension inside
the boundary layer during it's stop and go passage?

George Miller


Hello motorheads! As a pilot, I know something about laminar flow over wing
surfaces and I gotta think that the principle of physics is universal.
Laminar flow MEANS unimpeded parallel air passage over a surface. That
surface MUST be as slick as possible because impediments to that smooth
passage of air cause turbulence which (in the case of a wing) spoils the
lift. On a laminar flow wing, even the teeny bit of bumpiness caused by
frost makes takeoff a "no-go" condition until it melts. As Steve correctly
points out, rough surfaces do create eddies and may help to mix air and
fuel, but eddies do not smooth the flow--they ruin it. This is why porting
does so much good--it speeds up the flow by "straightening it out".
I have a 292 Yblock and am installing a 4bbl. When I was refinishing
the manifold, I noticed that the floor of the plenum right below the carb
throats was ribbed! They ended when the runners diverged from the plenum
chamber. Turbulence here seems like a good idea--mixes the charge better.
I also noted that the runners are rectangular and of constant dimension. I
remember an Edelbrock torker that I had on a MoPar 318 once and its runners
choked down as they approached the head. This is the "Venturi effect" which
speeds up the flow as the runner chokes down, ramming the air into the head.
Power is improved because the intake vacuum is assisted-- more charge moves
in with less work. The YBlock's reputation for being a poor breather seems
deserved. (But I can smoke 'em pretty good on antique night down at the
SuperK and nothing sounds like my YBlock growl!)
I guess I don't know why anyone would WANT to wreck the air flow near
their heads by intentionally roughing up the internals of their intake
runners.
Neal Forbes 54 F100 (Hot Heap)


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Date: Tue, 21 Jul 1998 20:49:31 -0400
From: Ken Payne
Subject: FTE Perf - Fellow Ford fan has passed on.

Just got some news that stunned me. Jim Osborn, of Jim Osborn
Reproductions, passed away Wednesday. Jim Osborn, in addition
to producing some of the finest reproduction decals, tags,
manuals and books for automotive enthusiasts, was also one
heck of a nice guy.

A couple of months ago, after having the pleasure of seeing
Jim's work first hand in his small plant, Jim offered Ford
Truck Enthusiasts a deal to help us continue to help our
fellow Ford truck fans. A discount on his products sold
through us. Jim didn't have to extend this offer, but he had
a genuine "I want to help out attitude." I know one of his
employees personally and can say that his workers truly
liked working for/with him. He was just an all around nice
guy.

For those who don't know, Jim founded the Mustang Club of
America and his lifelong dream was to start a Mustang museum.
His wife is planning on starting a fund to keep his dream
alive.

I'd like to take this opportunity to ask the members of these
lists to show that we're more than just about trucks. I've
made many friends here and I know from personal experience
that we have a good group here. Please, if you can spare a
few moments of your evening tonight or a few minutes tomorrow,
pick up a card and send it to:

Jim Osborn Reproductions
101 Ridgecrest Drive
Lawrenceville, GA 30045

If you want to, send a few bucks with a note stating it's
for the Mustang museum. Also, let them know its from an FTE
member, I think this, in a small way, will let them know
that we appreciated him.

Regards,
Ken Payne
CoAdmin, Ford Truck Enthusiasts, Inc.
http://www.ford-trucks.com


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Date: Tue, 21 Jul 1998 21:30:42 -0500
From: "Dale and Donna Carmine"
Subject: FTE Perf - building a 400

Hi Chris,
Thanks for the input on the roller rockers. Sounds like the $$ are better
spent elsewhere.
I already have the Edelbrock performer sitting in my garage and got a good
deal on a 750 cfm performer carb that is on the way now.

>Slow down the Mechanical advance in the distributor and limit the total
>advance. Then add more to the static timing.
Interesting......I thought that quicker advance was the order of the day,
but I guess you can't get any quicker than the initial static time.

>A set of Hooker Headers and a full dual 2.5 In. Exhaust system with a
>balance tube should be part of the build.
I will probably use 3" single exhaust because of the auxiliary fuel tank.
True duals are possible, but there's just not much room for two mufflers
when both pipes have to come down the right hand side.

>I have left the camshaft out of this as I do not know enough to address it.
>Do you need to pass an emissions inspection?
NO

>Automatic or Manual?
auto

>Street or off road?
Street

>Final Gear Ratio and Tire Size?
current rear is a 3.50 locker, no plans to change. Tires are stock, need
both wheels and tires but I don't know what I'll end up with yet.

>You are looking for a longer EX timing then intake.
I haven't selected a cam yet. someone else has suggested the comp cams
260H, I believe that this is a symmetrical grind, do you prefer the newer
asymmetrical grinds?
Basically this is a 4000 lb, 2wd truck. The only alteration from stock is
the locker. Needs to be a smooth around town and freeway performer where it
will see most of it's use with an ocassional jaunt into the mud or snow. I
think I would be very happy to get 275-300HP. With the stock 351M it won't
turn the tires on a good surface and takes 14.5sec 0-60mph. (yawn!)

TIA to all who respond
dale c

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Date: Tue, 21 Jul 1998 22:04:46 -0700
From: "Chris Samuel"
Subject: FTE Perf - Air Friction?

How is the term Friction being used in the Intake thread?
Do you actually mean that the air is being heated?
It is. but not enough to make a difference and only at the contact edge of
the Boundary Layer. I have not had time to double check this, but if I
remember correctly when you reduce the pressure of a gas you also reduce the
temperature. This is one of the reasons that a Carb will ice up.
OR
Do you mean drag; in this case Parasitic?
Which I believe is more what is being described.
The Boundary Layer is Parasitic drag just exactly like that on an aircraft
or anything that moves through the atmosphere.
CS


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