Vic,
Let me dream along a bit with your small block proposal. I don't need an
engine now, but yours is a fun idea. Keeping my foot out of the
throttle for 12 mpg would be a problem.
GM took the safe easy path by dropping in one of their better big blocks
with lots of cubic inches. I like this reliable brute force approach too
but there is a severe lack of speed parts available for the 455 when
compared to the Chevy V8 engines.
I would want a small block to produce at least 344 ft lbs. at 2400 rpm.
Torque should equal or better that of a stock 455 throughout the normal
operating range.
Long rod engines generally provide more torque at a slower rpm along with
good fuel specifics.
Large marine diesel engines are probably the most efficient IC engines to
date. They are very long rod engines that operate at very low rpm. Both
factors increase efficiency because fuel has more time to burn in the
cylinder instead of in the exhaust.
The point you make of the piston staying at top and bottom of the cylinder
longer is an interesting math relationship few gear heads seem to take time
to study and fully appreciate.
Turbo chargers use waste energy and pay back handsome especially in heavy
load applications. Most modern construction equipment and truck engines
have them. Turbos boost torque, increase efficiency, and ease the burden of
filling the cylinder with an adequate air charge. They have even more value
when operating in high country. I'm sold, I would want them.
The150 pound weight saving of a small block is attractive.
I would build a stroker to add cubic inches and go easy on boring to keep
the block strong. Like those long rods, longer stroke usually enhances low
end torque. There are strong stroker cranks available off shelf.
Pistons for a long rod stroker might not be available off shelf, but there
are companies who will make a set to your specs with the wrist pin bore
higher than normal.
As you say, small intake valves and manifold runners will keep airflow speed
up and favor low rpm efficiency.
Exhaust valves would be large with an efficient exhaust system to reduce
back pressure, same as with our 455's.
With turbos, I'm not sure I would spend money for aluminum heads, but one
advantage is less weight.
Ceramic coat heads, valves and piston tops to increase efficiency.
I would check out roller cams and roller rockers to reduce internal
friction. I would choose carefully in this area for long term reliability.
Balance and blueprint.
Cold temper high stress parts.
An 11 to 1 compression ratio with 87 octane fuel bothers me. Perhaps with a
computer controlled fuel injected engine and spark knock sensing it will
work. If it does, the higher compression will certainly increase
efficiency.
I'm still worried. Better add on demand water injection, just in case. The
best unit I know of, comes from England.
I would want a good speed shop involved who will develop my engine on his
computer before building it. Men who truly do this are rare in this
neighborhood. They seem to be younger ones who are more heavily into
computer aided engine research and development, NMC milling, etc.
Sometimes I help a local race engine builder iron out his computer problems.
Some of his software I play with includes Super Flow software for his
dynamometer and flow bench. The air flow development software is quite
interesting.
His engine development software is by a different vendor and will knock your
socks off. No garbage here, after you design with it, the dynamometer will
verify results, often within a couple of percent. It is fun to vary the
parameters and find results are not always what my old school thinking tells
me to expect.
Such a program would be valuable to tailor parameters for the low rpm
operating range I would want to favor, I especially want to run cam timing,
if nothing else. Custom ground cams are reasonable.
I'm no engine expert but do sometimes hang out with some.
Cheers,
Don Miller
75 Project
Shenandoah Valley of Virginia
Let me dream along a bit with your small block proposal. I don't need an
engine now, but yours is a fun idea. Keeping my foot out of the
throttle for 12 mpg would be a problem.
GM took the safe easy path by dropping in one of their better big blocks
with lots of cubic inches. I like this reliable brute force approach too
but there is a severe lack of speed parts available for the 455 when
compared to the Chevy V8 engines.
I would want a small block to produce at least 344 ft lbs. at 2400 rpm.
Torque should equal or better that of a stock 455 throughout the normal
operating range.
Long rod engines generally provide more torque at a slower rpm along with
good fuel specifics.
Large marine diesel engines are probably the most efficient IC engines to
date. They are very long rod engines that operate at very low rpm. Both
factors increase efficiency because fuel has more time to burn in the
cylinder instead of in the exhaust.
The point you make of the piston staying at top and bottom of the cylinder
longer is an interesting math relationship few gear heads seem to take time
to study and fully appreciate.
Turbo chargers use waste energy and pay back handsome especially in heavy
load applications. Most modern construction equipment and truck engines
have them. Turbos boost torque, increase efficiency, and ease the burden of
filling the cylinder with an adequate air charge. They have even more value
when operating in high country. I'm sold, I would want them.
The150 pound weight saving of a small block is attractive.
I would build a stroker to add cubic inches and go easy on boring to keep
the block strong. Like those long rods, longer stroke usually enhances low
end torque. There are strong stroker cranks available off shelf.
Pistons for a long rod stroker might not be available off shelf, but there
are companies who will make a set to your specs with the wrist pin bore
higher than normal.
As you say, small intake valves and manifold runners will keep airflow speed
up and favor low rpm efficiency.
Exhaust valves would be large with an efficient exhaust system to reduce
back pressure, same as with our 455's.
With turbos, I'm not sure I would spend money for aluminum heads, but one
advantage is less weight.
Ceramic coat heads, valves and piston tops to increase efficiency.
I would check out roller cams and roller rockers to reduce internal
friction. I would choose carefully in this area for long term reliability.
Balance and blueprint.
Cold temper high stress parts.
An 11 to 1 compression ratio with 87 octane fuel bothers me. Perhaps with a
computer controlled fuel injected engine and spark knock sensing it will
work. If it does, the higher compression will certainly increase
efficiency.
I'm still worried. Better add on demand water injection, just in case. The
best unit I know of, comes from England.
I would want a good speed shop involved who will develop my engine on his
computer before building it. Men who truly do this are rare in this
neighborhood. They seem to be younger ones who are more heavily into
computer aided engine research and development, NMC milling, etc.
Sometimes I help a local race engine builder iron out his computer problems.
Some of his software I play with includes Super Flow software for his
dynamometer and flow bench. The air flow development software is quite
interesting.
His engine development software is by a different vendor and will knock your
socks off. No garbage here, after you design with it, the dynamometer will
verify results, often within a couple of percent. It is fun to vary the
parameters and find results are not always what my old school thinking tells
me to expect.
Such a program would be valuable to tailor parameters for the low rpm
operating range I would want to favor, I especially want to run cam timing,
if nothing else. Custom ground cams are reasonable.
I'm no engine expert but do sometimes hang out with some.
Cheers,
Don Miller
75 Project
Shenandoah Valley of Virginia
