|
|
|
|
Original Message
|
| Coincidence! |
| By mark - 09/25/2001 9:35:31 PM; IP 216.228.198.201 |
Funny Richard should mention hemi - used to have a
426 that, back in the good old days, pretty much ruled
my little corner of the world. Ruefully have to agree that
now with the more modern chambers, the hemi is not
competitive in normally aspirated - ala Pro Stock.
But what do ALL the funny cars and fuelers use?
:-)
ANYWAY - Detonation resistance comes from a couple
things - 1 of which is the most possible quench area -
where a flat top surface of the piston comes close to
a flat surface of the head which is around or alongside
the comb chamber. That prevents a second flame front
from going to the edges of the cylinder and bouncing
back toward the main one (detonation). The twist wedge
heads with the matching Yates style dish pistons provide
a good example of that. I've got an article (emailable)
about a long rod 351w that ran a 220 duration 498 lift
cam, on efi, that could run 11-1 static comp ratio on 87
octane. Depending on the size of the heads (street or "R")
it put out either 380 or 400hp at 5000 and 430 or 450 torque
at 4000. About equal to a similarly cammed 393 stroker.
It also had excellent bsfc numbers, and was able to get
max power on only 32 deg max advance, another indication
of very efficient combustion. The twist wedge comb chamber
is a figure 8 as much in the center of the cylinder as is possible
to get a wedge and inline valve configuration. The Yates pistons
have the roughly figure 8 shaped dish also in the center, which
gives about as much quench area as you can get in a 2 valve wedge.
The long rods also help as they keep the piston closer to
top center during combustion.
There is an article on brand C that is similar - on
www.airflowresearch.com. They used an overbored
400 with a 327 crank and longer rods to also get 350+ cubes,
and of course AFR heads, that produced similar results.
The pent-roof is, of course, well proven. Look at the power
they get out of 1300cc's of Suzuki bikes etc, not to mention
Indy motors, etc. |
|
|
This thread, so far...
|
|
|
|
Post A Response
|
|
|
|
|
|