looking @ economy MPG engines in now time, they are all small cubes..wondering if anyone has ever destroked a 170..

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slant six's RULE!
http://www.usajon.com

A 3.125" stroke is just too much? 2.8 liters isn't all that much for a low tech engine like ours. If you want something smaller try a 2.5 or 2.2l K-car engine. If it has to be an I-6 try a Nissan RB20 or L24.

If fuel economy really is the goal get a SOHC Neon. I can cruise the highway at 75 MPH and still get 36 MPG. Stop and go economy isn't as good naturally, but it will still go 50% farther on a gallon than my Valiant and twice as far as my 2001 Dakota.

After basic repairs it's really tough to spend much money on a given vehicle in hopes of saving money through fuel economy gains. 10k miles at 20 MPG costs $2000 at $4/gal. Bump that to 25 MPG and you're down to $1600. If it cost you more than $400 to improve the economy a whopping 25% then it's not financially sound until you've driven more than 10k miles.

Going from my 15 MPG truck to my 30 MPG Neon saves 400 gallons/yr. assuming 12k miles/yr. Since I have less than $800 into the car and insurance is only $35/mo. The car paid for itself in about 9 months and now saves me about $90/mo. even after insuring the extra vehicle. Also, the Neon tires cost 1/2 that of the truck.

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Joshua

You would have to cut the rod journals down to something like a Honda rod bearing size to be able to destroke it, then use a differnt rod. Not that hard, but probably not worth the expense.


IMHO you could spend your time and effort into other parts of the engine to reach your goals. Things like getting the velocity up in the head and intake ports to match the cruise RPM, pushing compression limits, low drag rings, coatings like Micro Blue in the engine ( google it, pretty impressive), custom camshaft, ect,ect,ect............


There are many things that would yield better results than destroking. Infact you may want a good bit of torque to get good fuel mileage. The Micro Blue can be used in the tranny and rear end also. Then take things like aluminum driveshafts, lighter wheels, lighten the car. Aero drag on the car is a other area to work on.


Better fuel and timing control also could do a lot. IMHO, if I really did go the route of making the engine smaller I would sleeve the bore and make the pistons smaller, less weight, drag/friction, less timing the engine would need. Of course you could always do both,


Jess

Sometimes you just want to try something new....

I have thought about it, but don't know that anyone has done it. I am looking at building a 170 motor, but not into the build yet. I think 30+ MPG should be quite doable if the car is set up right. 35+ will be tough, but your thoughts about the little roadster could make that happen.

EFI, 5spd, and aero mods will help a lot...

Lou

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Home of Slant6-powered fun machines since 1988

Micro blue kinda looks like hibbity hoobla but who knows maybe it does rock!

Kev

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well someone stated 32 mpg on a stock featherweight duster..hwy.

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slant six's RULE!
http://www.usajon.com

With EFI and 2 throttle bodies you can split the engine in two (front half and rear half)


Cut off the fuel to the rear half, and then have the rear throttle body open up all the way for minimal pumping loses. (will work just about the same as valve deactivation)



Then you run on the front 3 cylinders............

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

Well newer cars are going with larger engines and getting better mpg. If an engine is too small it has to work harder than a bigger one, let alone the fact that 170-equipped cars had a higher geared rear-end.

I have a 170 and would never consider downsizing.

Im just asking if anyone has done this..I would not do this in a convential car..but a ultra light weight...

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slant six's RULE!
http://www.usajon.com

Never done this but you could off-set grind the crank and use some "brand-x" con rods combined shorter pistons.
Another option, Sleeve the block down to 78mm (3.071) and use some Nissan or ?? pistons, I come-up with a 139 ci size, based on a 3.071 bore and a 3.125 stroke.

While on the subject of "brain-farts"...
I have alway wanted one of the prototype aluminum block 170 engines... but have never been able to find one.

My "plan B" is to build a 170 "tall block", using the 225 aluminum block and a 170 crankshaft.
I am still working on ways "whip-up" the 7.700 inch "c to c" connecting rod it needs... and there are some options, short of making the rods from scratch... it's just time & money.
How does a 2.46 rod ratio sound?
DD

I've thought of taking an aluminum 225 block and relocating the head bolt holes 1-1.5" down by welding (or something), and shortening the deck ht by the same amt. This would both stabilize the cylinders, and give a lightweight low deck motor. Someday...

I think I'll need about $5k and one or two willing and skilled machinists and welders.

I wonder if you could CNC machine a whole top deck plate 3/4-1" thick with head bolt holes/bosses, and weld the whole thing to a shortened block? 209 ci, 250 HP, ~ 100lbs lighter than a stock early 225.

Lou

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Home of Slant6-powered fun machines since 1988

build it square 3.125 x 3.125.... my 120 ci harley aftermarket engine is square and puts 121 horse to wheel/ground...uses big block corvette piston blanks


kep on roddin'

Bingo! I have often considered it, but had never thought of synchronizing two throttle bodies. That's the missing piece. My brain will now go into overdrive as it ponders some more. Look what you've done to me...

However, the biggest advantage to cylinder deactivation is being able to do it on demand. A car with a tiny slant-3 wouldn't have the power to get out of its own way. If you want a small engine, build a small engine, and keep the aforementioned pumping losses away.

Many more thoughts on the topic, but perhaps I'll post over in the EFI section.

- Erik

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Lots of early Valiants and Barracudas have crossed my path.
Also a handful of other toys for variety now and then.