[DeTomaso] Ford 392 rev limit?

Fri Sep 6 14:49:33 EDT 2013

P.S. I wasn't talking about jumping out of an airplane with a parachute so
there was no need to mention velocity . A human being falling through the
atmosphere will reach terminal velocity ( approximately 120 mph) my point
was its not the speed of the fall that kills you (regardless of how you
"Plant your landing, you will be planted"  (or the speed of the piston per
se ) its the sudden stop and in the case of the piston the stop and 180
Degree change in direction (which at 7000 rpm means the piston is reversing
direction 233.333 times  per second.
I really don't want to complicate this furthur  but we have been speaking
about Mean piston speed which is the average piston speed through the
entire revolution. The question of Maximum piston speed takes into account
the fact that the  piston is accellerating for 1/2 of a revolution ,
stopping and accelerating again for the second half of the revolution .
When you look at these numbers you can get a much better idea of the forces
at work. If ther is anyone who isn't already board to death you can explore
this subject furthur at the following link.
Car Tech , Tech Tips piston speed
calculations<http://www.cartechbooks.com/techtips/pistonspeed>
B.C.

On Fri, Sep 6, 2013 at 2:16 PM, Boyd Casey <boyd411 at gmail.com> wrote:

> Once again the laws of physics make the call . Newtons second law;
> Momentum = mass X velocity.
> So the momentum of the piston will be effected by it's mass X it's
> velocity, so a piston assembly of greater mass will be more inclined to
> continue traveling in the same direction the greater it's velocity. So the
> key in designing the Piston and connecting rod assembly capable of
> withstanding the greatest RPM (piston speed) is to make them from the
>  strongest *yet* *lightest (lowest mass) * material available.  It also
> calls to mind the adage that "a chain is only as strong as it's weakest
> link. So as an example if you attempted to build a Cleveland engine using
> the best possible (strongest) crank, the best main bearings the strongest
> lightest valve train , strongest everything possible but you built it on a
> Cleveland block with a two bolt main your still going to self destruct at
> an RPM that an engine with a four bolt main would be able to withstand. An
> engine or any machine for that matter is equal to the sum of it's parts.
> You can't just throw in a forged crank and H rods and ignore everything
> else. An engine  is like the best detective in the world, push it past it's
> limits and it will find it's weakest point just like Sherlock Holmes always
> finds the culprit.. Piston speed is just a guide line that gives an idea of
> what level of build you are going to need if you have expectations of
> exceeding a given piston speed (RPM). Also if you have an engine that
> develops it's peak torque and horsepower at a given RPM range there is not
> allot of point in exceeding it by very much ( as Dan Jones Pointed out)
> because you won't go any faster. (By the way Dan Jones is an engineer and
> is the most knowledgeable person that I am aware of when it comes to
> Cleveland and Windsor builds). I have spoken about the Laws of Physics now
> I am going to quote the laws (or more precisely the "Rules" of Mad Dawg  )
> ( who I believe has been the most successful at campaigning Cleveland
> Powered Panteras in the Silver state and other ORR events)
> They are Rule #1 Dan Jones is always right, Rule #2 See Rule # 1. :>)
> I think like an under built engine we have over revved this subject line
> and it's ready to throw a rod!
> LOL!
> Boyd
>
>
> On Fri, Sep 6, 2013 at 12:25 PM, Doug Scott <doug at pickbbs.com> wrote:
>
>> When you jump out of a plane, there is nothing said about how fast you
>> are going, they only talk about how well you stick the landing.  The reason
>> I brought this up was simply to make sure all, that are reading this,
>> understand the actual issue with piston speed.  Not everyone has a good
>> understanding of the benefit and detriment of a longer stroke.****
>>
>> ** **
>>
>> Generally, the stronger parts are forged, but, the forged parts are
>> heavier as well.  So they put forged pistons and connecting rods in to help
>> keep the engine together, and in doing so, they add more weight that makes
>> the effect of piston speed more dramatic.  ****
>>
>> ** **
>>
>> *doug*
>>
>> ** **
>>
>> *From:* Boyd Casey [mailto:boyd411 at gmail.com]
>> *Sent:* Friday, September 6, 2013 11:32 AM
>> *To:* Melanie Disco
>> *Cc:* Doug Scott; mike Drew; detomaso at poca.com; Pantdino; Jeff Cobb
>>
>> *Subject:* Re: [DeTomaso] Ford 392 rev limit?****
>>
>> ** **
>>
>> Saying piston speed is not the issue is like saying jumping out of an
>> airplane is not what kills you , it's the sudden stop when you hit the
>> ground! The faster the piston is moving the more stress is induced when it
>> has to stop and change direction ****
>>
>> It's simple physics A body in motion tends to stay in motion  When a
>> piston hits the bottom of its power stroke and is traveling at 5000 fps it
>> wants to keep going, so if you have a weak crank, weak wrist pin  or weak
>> mains (to name just a few potential areas of stress it will keep going! You
>> can break criminal laws, you can break civil laws, but you can't break the
>> laws of Physics.****
>>
>> Boyd****
>>
>> ** **
>>
>> On Fri, Sep 6, 2013 at 11:07 AM, michael at michaelshortt.com <
>> michaelsavga at gmail.com> wrote:****
>>
>> I think because Buick had a 425 back then, Dodge had already made 426
>> famous, they (Ford) had 428 ...so 427 was left available. Marketing
>> probably made that decision is my guess.
>>
>> Michael Shortt****
>>
>> On Sep 6, 2013 11:02 AM, "Doug Scott" <doug at pickbbs.com> wrote:
>>
>> > Ford has known since the early 60s that short stroke, big bore is the
>> > recipe
>> > for race engines.  Take a look at the bore and stroke of the 427
>> compared
>> > to
>> > the 428.  Don't know why they call the 427 a 427 though, the
>> displacement
>> > is
>> > closer to a 425.
>> >
>> > doug
>> >
>> > -----Original Message-----
>> > From: detomaso-bounces at poca.com [mailto:detomaso-bounces at poca.com] On
>> > Behalf
>> > Of MikeLDrew at aol.com
>> > Sent: Friday, September 6, 2013 10:50 AM
>> > To: cengles at cox.net
>> > Cc: detomaso at poca.com; pantdino at aol.com; zumzum at cox.net
>> > Subject: Re: [DeTomaso] Ford 392 rev limit?
>> >
>> >
>> > In a message dated 9/6/13 6 44 23, cengles at cox.net writes:
>> >
>> >
>> > > FWIW: on the Speed Talk website Engine Forum, the professional
>> > > machinists and engine builders have commented that the factory crate
>> > > engines have been found to have, ahem, factory seconds used as parts.
>> > > It is perhaps not in all the engines, but it has happened often enough
>> > > that the pros have commented on it.
>> > >
>> >
>> > >>>They do make one hell of a spec sheet though:
>> >
>> >
>> http://www.fordracingparts.com/parts/part_details.asp?PartKeyField=10757
>> >
>> > I don't know if the engine in Jeff's car is *this* 392 or if they sold a
>> > lower-spec version.   It appears Ford has gotten out of the 392 business
>> > and
>> >
>> > gone completely over to 427 Windsors now:
>> >
>> > http://www.fordracingparts.com/crateengine/main.asp#tfo
>> >
>> > I've heard enough bad things about Ford crate motors from people who
>> have
>> > had them, that I would never get one.   They are absolutely fine for
>> street
>> > rods and things like that, or even for a Pantera that will only be
>> driven
>> > on
>> > the street, but for a Pantera that would see track duty (abuse) as mine
>> > does, there's just too much likelihood that something would let go....
>> >
>> > Mike
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