[DeTomaso] Intakes {rocker arms}.

[mark skwarek]

Dan,
When you used the tongues and port plates, did you also stuff the intakes and exhausts to match the raised floors of the heads. I'm doing this and am curious.
Thanks 
Mark

--- On Tue, 2/23/10, Daniel C Jones <daniel.c.jones2 at gmail.com> wrote:


From: Daniel C Jones <daniel.c.jones2 at gmail.com>
Subject: Re: [DeTomaso] Intakes {rocker arms}.
To: detomaso at realbig.com
Date: Tuesday, February 23, 2010, 2:03 PM


> Can you explain how the short ratio exhaust rocker arm improves the torque?

The reason the intake valve is larger (and port flow at a given
pressure drop is
greater) than the exhaust is because the intake is under atmospheric pressure
while the exhaust is under compression pressure.  Being under
pressure, the exhaust
blows down quickly in the lift cycle.  Dynamically, the exhaust side
is relatively
insensitive to valve acceleration but is sensitive to duration (how
long the valve
stays open).  The preceding is mainly a filling-emptying type of explanation.
Things are more complicated than this having to do with the unsteady
nature of gas
dynamics and the way finite amplitude waves travel within the exhaust
and I tend to
rely on wave action simulation to determine how any given engine may respond.
As a practical matter, Vizard suggests the best exhaust rocker ratio
is 0.1 to 0.2
lower than the intake ratio.  If you look at the cams used by most of
the competitors
in the EMC, they tended to have somewhat larger exhaust duration but
shorter lift
(either by the lobe chosen or a shorter rocker ratio).

We also found the exhaust port stuffers (MPG Stinger type) worked on
both long tube
headers and the Pantera GTS headers.

Port Plate Test
Same setup as pull number 10 with the Strip Dominator HVH intake setup and
Pantera header.  The Pantera header comes straight out from the cylinder head
whereas the Mustang Hooker header turns downward more quickly.  In both cases,
the Stingers helped.

Without Stingers
RPM     HP      Torque (ft-lb)
4000    278.7    362.9
4100    291.9    370.3
4200    294.8    369.3
4300    301.1    368.1
4400    308.9    369.0
4500    319.2    372.6
4600    331.7    378.5
4700    345.3    385.5
4800    356.9    390.1
4900    363.5    389.9
5000    372.8    390.4
5100    378.2    389.6
5200    382.4    386.5
5300    389.9    386.4
5400    396.7    385.9
5500    403.1    384.9
5600    407.6    382.3
5700    408.0    375.7
5800    405.9    367.4
5900    398.5    355.2
6000    395.4    346.2
6100    399.0    343.4
6200    404.4    343.6

With Stingers
RPM     HP      Torque (ft-lb)
4000    278.7    366.3
4100    286.2    367.0
4200    297.4    372.0
4300    310.4    378.8
4400    322.4    384.7
4500    333.8    389.6
4600    343.4    392.2
4700    353.6    395.0
4800    365.5    399.6
4900    372.6    399.7
5000    376.0    395.1
5100    385.4    396.4
5200    388.9    393.2
5300    395.0    391.3
5400    404.5    393.0
5500    411.0    392.4
5600    410.4    385.1
5700    404.9    373.3
5800    406.1    367.6
5900    407.6    362.5
6000    402.5    352.7
6100    400.9    345.8

Dan Jones
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