Neil,
I beg to differ. I will agree that as factory built, Hemis did not usually
come close to their potential, with the exception of the performance models.
Compression ratios, cam profiles, ignition curves, etc., were conservatively
designed for economy, reliability, and drivability, not performance. They
were further handicapped by 2 speed automatics and low torque converter
stall speed rpms.
Engines with small valves, heads with small ports, small cams, and small
carbs usually generate more torque at low rpm, because they have faster air
velocity into the cylinders, generating a slight ram effect. They also make
better gas mileage. They do not perform well at higher rpms. This is what
most casual drivers of new cars want, because they do not often exceed 3000
rpm. BUT, this is not what I want.
Power, both horsepower and torque, are a matter of how much air/fuel gets
into the cylinders. Hemis simply allow more airflow. More is better. Much
more is much better! With a proper balance of specifications, a Hemi will
exceed any other equivalent cid engine, even at low rpm. I have driven Poly
2 bbls, Poly 4 bbls, and Hemis (all same cid) in a 56 Dodge. The Hemi
performs the best, even at low rpm.
One cannot compare early Hemis (1951 Chrysler 331 cid Hemi at 180 hp) with
later Polys (1957 Dodge 325 Poly 4 bbl at 260 hp). Their internal
specifications were vastly different. The 1957 Dodge D500 325 cid Hemi 4 bbl
was 285 hp. The 1957 Chrysler 300 Hemi at 375 hp was a vast improvement over
the 1951. I would expect that if one were to build 2 engines with identical
internals, one Hemi and one Poly, the low rpm performance would show little
difference, and above 3000 rpm the Hemi would be superior. If a Hemi is
modified with a more aggressive cam and ported/polished heads for more
overall performance, it may suffer a slight loss of torque at lower rpms,
when compared to an unmodified Poly. Similar mods to a Poly would have a
similar effect on low rpm torque.
The Hemi owes its superiority to the fact that the head ports are straight
in and out (the valves point toward the intake and exhaust manifolds) and
the air/fuel flow does not lose velocity going around corners. The Poly head
engines were a compromise to lower costs, but still maintained much of the
same benefit and only a small drop in efficiency. Wedge motors make the air
go around sharp corners in the ports, which slows it down.
Way back in 1956, D500 Dodge Hemis were drag raced starting out in 2nd gear
(because of the poor 3 speed manual ratios available) and were THE FASTEST
"stock" car in the 1/4 mile anyplace on the planet! This is not an example
of poor torque. Ask Arnie Beswick.
And Gary's 318 Poly (MoPar Muscle, 10/01) is bored and stroked and heavily
modified to achieve 405 hp from 402 cid. Not much better hp/cid than the
factory stock 1957 Dodge Super D500 Hemi at 310 hp from 325 cid. Similar
improvements to the Hemi would achieve even higher hp/cid ratios. My DeskTop
Dyno software predicts that if I bored and stroked and similarly modified my
1956 Dodge Hemi to 350 cid, it would put out over 400 hp too.
Dave Homstad
56 Dodge D500
-----Original Message-----
From: Forward Look Mopar Discussion List
[mailto:L-FORWARDLOOK@xxxxxxxxxxxxx]On Behalf Of eastern sierra Adj Services
Sent: Thursday, April 03, 2003 7:43 PM
To: L-FORWARDLOOK@xxxxxxxxxxxxx
Subject: Re: [FWDLK] New Acquisition
Hi, Tim, I'm just getting home, & enjoying the "Hemi- Wars" thread.
The early Hemis couldn't get out of their way, until they reached about
30 mph--My engine is bored 40-over (call it 330 c.i., now, has a "3/4"
cam, hollow-adjustable pushrods, "440" lifters, balanced crankshaft,
ported/polished, standard carb (overhauled, with anti-washout bushing)
a 'worked' torque converter (higher-stall; it BARELY even moves, @
idle--how nice!) a 'converted' h.d. WATER-COOLED trannie (John Veatch
springs/weights) , but it still needed a 3.55:1 SureGrip in order to
accellerate, from a full-stop.
I know all-about Uncle-Tom, & have his Hemi/D500 articles (you are
referring to his 4/57 road test) from 1953 -1961; he made no "D500 "
test in 1958, darn it).
Unk-Tom was known for some hyperbole, & later-in-life was known to DENY
ever having made that wonderful 1958 Chry/Imp -vs- Fxxx/Cxxx
comparison-test ( which happened to have been made @ Manzanar's
abandoned
airfield, which is about 45 miles south of my home)!
A Hemi driver always tried to drag-race, from "the roll" ; never from
"the dig".
-----Original Message-----
From: Forward Look Mopar Discussion List
[mailto:L-FORWARDLOOK@xxxxxxxxxxxxx]On Behalf Of eastern sierra Adj Services
Sent: Thursday, April 03, 2003 1:13 AM
To: L-FORWARDLOOK@xxxxxxxxxxxxx
Subject: Re: [FWDLK] New Acquisition
Hi, Owen & Jo, et al ; notwithstanding your 300-C's amazing performance
off the line, it is 'universally' accepted that the 'factory' Hemi, even
in 426 configuration was a 'slug' . The 440 wedge outran the 426 Hemi
until almost @ the end of the 1/4 mile. Why do you suppose that Chrysler
offered rear end ratios up to 6.18 (or whatever?). The Hemi "came-on"
its cam at about 30 mph. At the 'time', wasn't the VW beetle the
world's fastest car, up to 30 mph? Power-to-weight.
As far as the 392-cars are concerned Chrysler designed the chassis, to
accomadate the engine weight. I kind of shudder to think what a 354/392
would do to the handling of a stock suspension pre-56 MoPar. The pick-up
truck w/a Hemi spins its wheels because there's no weight on the rear
wheels. 4x4 pickups are lousy in the snow, for that reason.
Oh yeah, please see MoPar Muscle, 10/01, to see what can be done to a
little-ol' LIGHT-WEIGHT 318 Poly - like 405 HP @ 5,600rpm , & 442
lbs-ft./torque @ ONLY 4,400 rpm! -Normally aspirated/no-NOS .
And, I'm kicking myself, trying to recall, now, where I just read about
how-nearly-perfect is the flow-rate on the Poly heads.-Anybody else
recall that reference?
Neil Vedder
(that ol' Poly-lover)
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