Am I the only one wondering what Jim does that he has enough money
laying around to give out 12 sets of roller rockers??
Tim Holbrook
1971 TR6
--- Jim Swarthout <jswarth1@tampabay.rr.com> wrote:
> From: "Jim Swarthout" <jswarth1@tampabay.rr.com>
> To: <6pack@autox.team.net>
> Subject: RE: TR-6 performance (update)
> Date: Tue, 3 Dec 2002 16:11:16 -0500
>
> To the list:
>
> Especially those who may be getting in on this late!
>
> I would like to see 12 TR-6/250 owners with basically stock
> engines...
> (No wild cams or other major mods to the valve-train)...install a set
> of
> these rockers and write back with comments...good or bad.
> Nitrous...or
> some form of forced induction is fine. Triple carbs and a
> header...fine.
>
> The reason that I would prefer to give these away to owners of stock
> cars is that I don't know that they will be of any benefit on a
> modified
> engine. I can only speak for the performance increase in a stock
> engine.
>
> If any one of the conditions below describes you! Then please don't
> ask!
> It costs me money to make them. I want to be sure that they will be
> properly installed. I want to know that they are being installed by
> an
> owner who enjoys the performance of these cars and will be able to
> write
> back with comments more elaborate than...Gee I almost didn't want to
> put
> the valve cover back on..."These rockers look cool".
>
> You don't own a "6" or a "250"
>
> You don't like to work on your car...garage queen...open wallet at
> the
> local shop...AND...NO...DON'T TAKE OFFENSE...It's just simply that
> this
> won't work for this test.
>
> You drive your car refusing to see the tach go beyond 4000 RPM's.
>
> Your car is currently scattered all over your garage...and it will be
> next year before you will get around to installing the rockers. I
> would
> like to get feedback promptly.
>
> Current standings:
>
> Kai, graciously declined, forfeiting his answer to someone else.
>
> Jamie Palmer
>
> #3) What does an air pump, (smog pump), do? Explain the entire
> cycle...peripheral equipment!
>
> Pumps in air into the exhaust stream right at the cylinder head,
> theoretically allowing unburned hydrocarbons to combust while in the
> exhaust stream.
>
> Hugh Fader, Mark Hooper
>
> #12) If the piston to be fired is approaching compression...(15
> degrees
> BTDC)... and you have the timing set to fire at 10 degrees Before
> TDC...why doesn't the piston travel back down...moving in the
> direction
> from which it just came...?
>
> First of all, the piston is not approaching compression. Compression
> is
> nearly completed at this point. The simple answer is that the force
> on
> the top of the piston is less than the force on the bottom.
>
> Forces on the bottom of the piston are: crankcase pressure acting on
> the
> piston bottom, inertia from the spinning crank transmitted through
> the
> connecting rod, and in a multi-cylinder, forces from other pistons on
> their expansion strokes transmitted through the crank and rod. Oh, I
> almost forgot the inertia of the piston itself.
>
> Forces on the top of the piston are: pressure due to the compressed
> gas
> acting on the piston top and pressure due to combustion.
>
> Now, in an optimally timed combustion event (MBT), peak cylinder
> pressure occurs about 12-14 degrees after top dead center. The
> combustion pressure has yet to even get started developing at
> ignition.
> So the force due to combustion cannot overcome the other forces at
> this
> point.
>
> Hugh Fader's answer while correct is limited in that he omits to
> mention
> that although ignition of the gases is almost instantaneous at the
> spark
> point, the flame front still has to propogate thoughout the
> compressed
> gases and then raise their temperature to the point where they press
> against the piston (and cylinder walls/head of course) with the force
> required to drive the overall engine. It is this propogation that
> actually chews up the time and requires the preset of the ignition.
> Once
> uniformly ignited, a correctly designed engine can have a much
> smoother
> action by having the gases continue to burn and heat well after TDC
> and
> with correct engine sizing, maintain anconstant cylinder pressure
> even
> though the piston movement is changing the cylinder volume in a
> non-linear fashion due to the eccentric crank movement.
>
> Shane Ingate
>
> #9) You're speedometer shows 60MPH. You're Tachometer shows 3000
> RPM's.
> You're in 4th gear at 1:1 with a final drive ratio of 4:10. What is
> the outside diameter of your tires?
>
> 27.56"? (I can only remember PI to 3 significant figures). If that9s
> the case, this is pretty close to a 215/70-15 tire.
>
> Stephen Hanselman
>
> 1) There were 2 reasons why electronic ignition was developed? Both
> answers pertain to the consumer, or auto owner.
>
> In my mind electronic ignition was developed first to get a hotter
> spark. My dad put together one back in '67 or '68 for our Plymouth.
> He
> found one problem in the spark coil though, the fire was so "hot" it
> would arc over the top of the spark coil. Now days, driven by the
> left
> coast again, emission requirements are so tight that pulse to pulse
> timing is a major factor in controlling what comes out the tail pipe.
> This, of course, has no relation to any increase/decrease of power
> out
> of the engine.
>
> Vance Navarrette
>
> 5) What performance gains will you achieve by installing a long
> duration...(extended period of valve opening)..., high lift, camshaft
>
> in an otherwise stock engine?
>
> As they say, "It depends". All other things being equal, this is
> true.
> But if the cam is *TOO* big, you will end up with less power
> everywhere
> in the RPM range, because the rest of the motor cannot keep up with
> the
> big camshaft's demands at high RPM.
> Also, if the lobe centers are closer together, a longer duration
> cam might give more power *LOWER* in the RPM range than the stock
> cam.
> Lift and duration are not the only cam parameters that affect amount
> of
> power and it's location in the RPM range. Two other very important
> factors are lobe center spacing (in degrees) and valve acceleration
> (in
> inches/degree**2).
> The above is why it is simply impossible to compare cam timing
> and draw conclusions about which is "best" except in a very broad
> sense.
> The cam manufacturers do not give enough information about their
> profiles to make precise comparisons. You cannot even compare the
> rated
> durations because there is no standard method for measuring them. The
> only values you can compare are net lobe lift and duration at a known
> lobe lift (most often 0.050"), and many cam makers will not even give
> you that much information!
>
> Thanks to those of you who have participated!
>
> If I have left anybody out...please let me know.
>
> I realize that many of you answered all of the questions...I simply
> chose one to attach to your name.
>
> 7 more to go...
>
> Answers to questions 1,3,5,9 & 12 are spoken for.
> 2,4,6,7,8,10 & 11 remain
>
> Don't copy/paste I'll know.
>
> Jim
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