So I have been kicking an idea back and forth in my head for a while,and decided to seek professional help for it!

Im picking up my 67 Dart this weekend.Stock 1 bbl 225 slant.While I am driving it stock and doing all the little things(fuel line mod,hei ignition conv.,disc brake conv.etc...) I want to start building a replacement engine,slowly over a amount of time/funds. I want to build a slant for a good amount of power and gas mileage.The dart has a 904 behind it and my plan is to retrofit a gearvendors overdrive unit from a motor home to my dart.Effectively giving me 6 gears and a nice overdrive. So I was thinking: Less cubes=Less fuel.

I have been trying to find a 198 engine,with no luck so far.What do you guys think about using a 170 in a 67 dart? With the head ported,good cam,4 bbl intake,yadda yadda etc... will it have to work too hard to move my 67,even with those upgrades?

My other idea is: Is there any way to DE-stroke a 225 to get less cubes?

Whats everyones ideas and opinions on this matter? What would YOU do? I want a fun little engine,that has the ability of getting good economy when I can behave myself...what say you?

Also a little of where I am comming from:
My current daily driver is a 07 honda fit,due to being laid off twice this year,and getting a job that pays 1/3 of what I made before,I can no longer afford the payment,so I must give it back to the bank.

This car has 1.5L with 109 h.p and I think 94 ft. lbs of torque,and with a 5 speed I think this car is fun! So I dont need gobs of power to be impressed obviously

Also, dont worry.I dont expect the slant to get anywhere near the m.p.g's I get with my honda! I get 35 in town and 44 highway if I drive 65. I just want somewhere in the mid to upper 20's,with about a million smiles per gallon.

i guess if you put a 170 crank in a 225 block, would that make a "super" long rod?

zedpapa

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1970 dodge dart w/225 /6 bored .040" over, holley 390cfm w/vac. sec., compcams 252s, clifford shorty headers w/2.5" exhaust w/flowmaster, f-body 11" front discs, aluminum A-833OD, 8 1/4 w/3.21 SG
soon to have 5 gears!!!

Well, if you can find a gearvendors unit that will bolt up to a slant six 904, that might work. However, I think you would be better off keeping a 225 unless you also plan on increasing your rear axle gear ratio to a lower ratio (higher numerically) When you build a motor to achieve your goals, you really want as much torque as possible. The 225 is the best motor for torque. 198s are very hard to find. The only way to de-stroke a 225 is to install a 198 crank and con-rods, in which case you will already have had to purchase a 198, so why bother?

My advice would be too find a 225, keep the valve size stock but do some clean-up porting, keep a one barrel or small or staged two barrel carb, switch to the 71-80 stock mechanical cam, upgrade exhaust to dutra dual exhaust manifolds which have two 2 inch pipes that combine into one 2 1/4 inch pipe, and switch to electronic HEI ignition with a custom curved distributor. A cold air and heated air intake system would be a good idea too.

A manual five speed transmission would be far cheaper and easier....

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Casually looking for a Clifford hyperpak intake for cheap.

Im able to get the gearvendors for around 800,in good shape.Then all I need is the adapter from GV(I think like 100-150) and I can bolt it in just by widening the trans tunnel a bit. The wife cant drive stick,and I dont want to cut this car up! Its a 67 Dart GT with 80,000 orig. miles.Buckets with automatic console,and I want to keep it that way!

Also a gear swap is already in the plans,when I swap the 7 1/4 for a 8 3/4.

i would use the 225 mainly if you are in an area with hills a 170 will hit a hill and go from 45 to 35 in the blink of an eye. 225 and do a small amount of head work for better flow and i would get a shift kit for the trans and gearvinders still makes over drive if you want to go new but id go used that wont be 2 grand http://www.gearvendors.com/hrdodge3s.html
904 is at the bottem of the page
or get you a set of 2.76 gears and that would drop your highway rpms

then get a super six they can give a big bump in hp (5-10 maybe) and milage and some dura duels and 2 inch duel pipes out the side with glass packs and maybe a towing cam

BUT more torque more mpg and smother acceleration

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1973 plymouth duster 225 slant six .30 over, erson 270 cam, 9.5 to 1 compression, big valves, headers, and a holley 4 bbl
http://cardomain.com/ride/3135091

hey that thing got a hemi? naw its just a slant six

GENT,

I was thinking along those lines when I rebuilt my engine two years ago. However, keep the 225 platform and build it for torque. Do a search for my build (mileage and torque). As you can see below, I custom built a 8 3/4 2.76 posi for mine. It keeps the rpms down, right in the pocket for torque and good gas mileage.

Following Doc's suggestions during the build, the engine came out perfect! and very, very spunky for a SL6. It is allot of fun to drive.

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

Sounds like I should keep the 225! Would I lose much torque if I eventually find a 198 and build that? The Dart I am buying comes with a COMPLETE super six set up,has kickdown and even the 2 1/4 headpipe! The reason I want the Gearvendors OD is because I can get it for so cheap.I have a connection that will sell me one that has been inspected and has a fluid change for only 800,then I just have to get the adapter for the 904!

I will definatly be buying the dutra duals,already have a deal going with Doc But I will be Y pipeing it into a single exhaust. I was thinking,do any of you think the AussieSpeed manifold will offer any m.p.g/power improvements over a stock super six manifold?I love the wicked looks and feel that with long equal length runners it might offer better torque and possibly better mileage

Thank you everyone for your ideas and opinions! Keep the comming!

-GENT

Well, I'm a little lost on your goals and wants? If it is gas mileage the 225 is the best bet, especially since you could keep the higher rear end and perhaps an overdrive. I would assume your searching for a little motor in less motor less gas?
I would disagree that the 225 is a better motor. Read the RPM limit thread for more reasoning, but it boils down to two things. The Raised Block and long stroke really fights itself and creates torsional loads on the mains. A big deal? Probably not huge but a major facter when trying to turn revs. The next idea is that they all share a lot of the same stuff right? And in short your head wants to match or exceed your size in flow. So a head designed for a 170 that flows lets say 160cfm would be a kinda weak sauce on a 230 correct? On the same token if your port and flow it to 200cfm imagine what that would do to the 170. So am I bashing the 225, no, just stating some stuff that I look for when building engines. Of course I always chose the 302 over the 351C.... so maybe I take different paths.

Im not going to lie,your post made my head spin a little.What are you asking/telling me?

Don't worry too much about it. Within reason a larger engine turning slower can usually achieve the same economy as a smaller one turning faster. If you're serious about economy and the use of the overdrive I would also suggest a lockup torque converter and transmission. Running low engine speeds with highway loads leads to increased torque converter slippage and power lost as heat in the transmission fluid. This heat of course comes from burning fuel in the engine and a loss of economy.

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Joshua

Where can I find a lock-up trans/converter to fit the slant?How much would it cost?

Nearly every slant six 904 transmission manufactured post 79 is a lock-up tranny. There are a few oddballs such as 1986 california truck and van 904 trannys (nonlockup), but the vasy majority are.

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Casually looking for a Clifford hyperpak intake for cheap.

Is it a good lock-up trans? Any troubles with these transmissions?

The 904 is a fairly stout design. There have been many documented instances of these transmissions going three and four hundred thousand miles without even a filter change. The lockup transmission inceases efficiency slightly and doesn't really affect durability or reliability.

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Casually looking for a Clifford hyperpak intake for cheap.

How about performance? Any affect on that?