170 vs. 225

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mathewdylang

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Talking to people on the / board, they said that the 170 shorter stroke would probably be better with a turbo. I hadnt thought about that in my looking. I know my duster was a factory 225 with a 3spd. I was going that way for that reason.

Can someone give me pros and cons to boosting each motor? Obviously the 170 could use Smaller turbo, which might give me a few more choices in turbo. Other than that whats everyones input?

Thanks in advance,
Mat
 
Maybe I should have chosen different words. Maybe "better" isn't what I was lookin for. When you go forced induction, cubic inch displacement doesn't matter as much as going N/A. That's probably a better way to put it. There are a LOT better people than I to help you. I am sure they will chime in and we might BOTH learn sumffin. lol
 
Maybe I should have chosen different words. Maybe "better" isn't what I was lookin for. When you go forced induction, cubic inch displacement doesn't matter as much as going N/A. That's probably a better way to put it. There are a LOT better people than I to help you. I am sure they will chime in and we might BOTH learn sumffin. lol

The various "hot rod associations" such as NHRA and IHRA have always classified modified cars according to their weight, divided by their engine displacement, with the exception of a few "spec classes" like Pro Stock..

The difference in a 170 and a 225 is virtually 33-percent.

ONE-THIRD.

That's lot to make up.

The 170 has one thing going for it; having a one-inch shorter stroke than its 225 brother, it loves to rev...

But, that's it.

EVERY OTHER engine specification relative to output at full throttle gives the advantage to the bigger motor.

In certain classes of competition (in organized drag racing) the 170 has the advantage, but in the (street driven) real world, there is no comparison.

Unless you're running an NHRA or IHRA class with your car, and it's a pound-per-cubic inch class, there's no eathly reason to give away 33-percent of your engine's power-making capability.

One reason might be if you were looking for that last mile-per-gallon of fuel economy.... but, I can't think of another.

Hope this helps...:cheers:
 
Not trying to cause an argument Bill, but I've seen you pretty much echo my point about cubic inches not being really important with forced induction. Now of course when I make the point, I get disagreed with. That's cool. And typical. Mat, just disregard my opinion on this. I was trying to help, but obviously I went the wrong direction.
 
The few things I have learned in the last few years (that I can remember) is .............. The slant six head was designed for the 170/6, and was never changed for the longer stroke bigger bore 198/ and 225/, I agree with Bills finding that C.I. is a plus for getting more power easier then it is by trying to get bigger numbers with a 170/6 (low deck) block.. all of the 170/ engines have a steal crank and larger rod and crank bearings, witch will handle more boost or Nos, the early 225 engines also have steel cranks and big rod and crank bearings till 197?, but at one time (not sure) they went to a cast-iron crank and smaller bearing size..( I could be wrong on this bearing/gernal size) So if and when I go 225/6 the head work is going to be a must do for the bigger bore and longer stroke and it will net more H.P.
H.P.
170 1967-1969 8.5 to 1 115 @ 4400 155 @ 2400
225 1964-1971 8.4 to 1 145 @ 4000 215 @ 2400 note,this big hp, compared to the rest of the 225/6 engines
225 1972 8.4 to 1 110 @ 4000 185 @ 2000
225 1973 8.4 to 1 105 @ 4000 185 @ 1600
225 1974 8.4 to 1 105 @ 3600 180 @ 1600
225 1975 8.4 to 1 95 @ 3600 170 @ 1600
225 1976-78 8.4 to 1 100 @ 3600 170 @ 1600
225-2V 1977-78 8.4 to 1 110 180

This info was found here http://www.allpar.com/slant6.html
 
What was the cause of the big dropoff in HP on the 225 from 1971 to 1972? Or was that just a different power rating system causing the number to drop? I read through the allpar article but didn't notice an explanation for this. In other words, in looking for a transplant or engine to build, is there any actual reason that a '71 or earlier 225 would be better than a '72-up one?
 
From what I seen on that right up they went to a cast-iron crank and smaller bearing size for weight loss and less friction figuring the cast iron crank will handle what power the slant 6 will make. Learn something every day, but I have herd the smaller bearing size have and can throw a rode out the side of the longer stroke 225, #4 I believe
 
The 170 would give me the higher revs, but as a street toy i dont know how often i would need big revs. And the slightly bigger motor would probably be better for messing with v8 cars around town. Thanks everyone for your input.
 
I cannot offer any advice to boost-- I can however tell you a 225 hands down smokes a 170 for breakaway performance.

I had a 1962 valiant 170 push button traffic-- could not get inot traffic in Wichita Ks--(flat) swapped in the 225(used low mileage engine) car ran totally different. I only changed the exhaust to mate up to the taller point-- used the same ignition & carb set-up (carter 1bbl & petronix).

vast improvement -- easily entered into traffic after the swap.

Car is still driven today.
Lawrence
 

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Not trying to cause an argument Bill, but I've seen you pretty much echo my point about cubic inches not being really important with forced induction. Now of course when I make the point, I get disagreed with. That's cool. And typical. Mat, just disregard my opinion on this. I was trying to help, but obviously I went the wrong direction.

I probably over-stated the case for displacement advantages in this discussion about the `70/225 comparison, true. If you just want to make horsepower, you can spin a boosted 170 a lot faster than a 225 and probaBLY MAKE ABOUT AS MUCH TOTAL HORSEPOWER AS THE BIGGER MOTOR, BECAUSE THE 225 IS GOING TO THROW IN THE TOWEL AT ABOUT 5,500 RPM WHILE THE 170 WILL CONTINUE TO SEE HORSEPOWER CLIMB FAR BEYOND THAT DUE TO THE FACT THAt it has a MUCH shorter stroke AND the exact same cylinder head as the bigger motor. Sorry for the caps; I am a two-finger typist and have to watch the keyboard, not the monitor, and can accidentally hit the caps lock key and never know it....

Anyway, yes, the 170 is not that handicapped when it comes to making pure horsepower, but when driving around town, stoplight-to-stoplight (not racing,) the 225 will have a lot more off-idle torque to get the car rolling, and make daily-driving a much more enjoyable experience, I think. It's a driveability thing having to do with available non-boosted torque, but not total performance.

At the strip, there might not be that much difference, but the 170, in making those big numbers, would probably need to run somewhat more boost and wind up a lot tighter. WHICH IT COULD... just a different "build" in terms of valve train technology to accommodate all those r.p.m.s, which the 170 needs (and, is capable of, properly built) to achieve the horsepower numbers of a lower-revving 225.

I apologize, Rusty, for mis-stating my case; you were right all along...:eek:ops:
 
Yep! I am keeping my eye out for a 225/6 to do a up grade to the 170/ that Victoria is cradling now, but it's going to be hard to pull a perfectly good running engine when the time comes :mrgreen:
 
I understand both sides. I had a 93 eagle talon tsi that low end power wasnt huge but get about 3500 and up to 7500 rpm it screamed. Im guessing it would be the same for the 170. Where as my cousins v6 turbo had more off the line with the larger 3.0 but couldnt get it to breathe as long. Which is what would happen to the 225. I dont intend to make it a track car. Just fun to play with and mess with some people. Maybe make it "quick and able to corner". But i think the 225 is better suited for my around town toy as it will probably not see more than 5500rpm.
 
I apologize, Rusty, for mis-stating my case; you were right all along..

That's highly unlikely.


I'll put it like this. If I HAD a 170 (and I do) and I planned on a turbo motor, I would not go to the trouble to find a 225. At least not for a street car. I would use what I already had.
 
I understand both sides. I had a 93 eagle talon tsi that low end power wasnt huge but get about 3500 and up to 7500 rpm it screamed. Im guessing it would be the same for the 170. Where as my cousins v6 turbo had more off the line with the larger 3.0 but couldnt get it to breathe as long. Which is what would happen to the 225. I dont intend to make it a track car. Just fun to play with and mess with some people. Maybe make it "quick and able to corner". But i think the 225 is better suited for my around town toy as it will probably not see more than 5500rpm.


Well, you didn't ask (nobody did!) but here's my opinion of your scenario...

Ten pounds of boost on a 225 can produce about 320 horsepower (flywheel) which is an amazing wake-up call for a slant six. In order to enjoy long-term mechanical health, you'd need to install a water/alcohol injection system, I think, and run premium (91-93 octane) gasoline... and if I were doing it, I'd pull the head and not port it ($$$) but, install some larger (1.714"/1.5") valves and 340 valve springs (cheap.)

You'd end up with a pump gas engine that would pull a 3,300 pound A Body into the 13's and maybe faster. You'd need to swap in a 2.76-geared 8.25" rear end from an Aspen/Volare, or very late A-Body.
The stock ignition should work fine, but you'd definitely (and, this is of CRITICAL IMPORTANCE!) need to limit your total mechanical spark advance to eighteen degrees. That is, set your distributor (retard it) so that no way can that engine EVER see more than eighteen degrees of advance in the crank, Vacuum advance doesn't count; it will go away as soon as there's no vacuum, which happens when the throttle is opened a goodly amount... and/or, it goes on boost.

A 500 Holley 2-bbl modified for blow-thru on a Super Six 2bbl manifold would be a great induction system for this motor,

A stock torque converter is all that is needed.

Have fun!!!!!!!!!!!!! :blob:
 
Bill thats good insight. Thanks for posting. I think im going 225 if i can get my hands on one. For this scenario what turbo should i look into. Because 10 pounds on a small turbo is nothing like 10 pounds on a large turbo.
 
I have a 225 block with all the machine work done and a standard steel crank, but I am in Georgia.
 
Bill thats good insight. Thanks for posting. I think im going 225 if i can get my hands on one. For this scenario what turbo should i look into. Because 10 pounds on a small turbo is nothing like 10 pounds on a large turbo.

You need to ask that question of someone who knows what they are talking about; I really don't. Our turbo is a 66mm Turbonetics, plain-bearing, non water-cooled. very basic unit with an external waste gate. We have had NO trouble making 15 pounds of boost with it and it's begging to be let loose.

I am thinking that you might fare well to get a 1987 Buick Grand National (3.8 liter) turbo in good workking order from a junkyard; they have a built-in wastegate... one more thing you wouldn't need to buy.

Tom Wolfe (FABO member shaker223) bolted one with a 4bbl and ran 12.95 @ 104mph with an otherwise stock engine. That was with 21 pounds of boost, however.

Here's the video of that run:[ame="http://www.youtube.com/watch?v=pPe_vHwZsF4"]Slant Six Turbo 1970 Dodge Dart 1/4 Mile pass - YouTube[/ame]

Everything stock except for the turbo and a Holley 4bbl....

There are lots of ways to do this... You're on the right track!

Have fun.:blob:
 
The advantage of a 170 over the 225 is its ability to rev. With a turbo, that is irrevalent. You don't need or want high rpm. Personally I would use what ever engine I had available. That is what I did in 1979. I used the 170 that was in my car, already (didn't have to buy another motor). Used a Corvair turbo, which was used on a 168 cid engine (perfect match). At that time there was very little info available on turbo size matching.
 
B.D,nice low dollar combo. Nice return, for the dollar.(and v8 different).
 
B.D,nice low dollar combo. Nice return, for the dollar.(and v8 different).

Thanks Bomber!!! I forgot to mention an important part of the prescription, though; the exhaust manifold/turbo mount.

PISHTA came up with a grand idea of setups like this where drag racing is not the premier activity for the car.

He buys a 2.25" J-pipe (exhaust tubing) and welds a flange onto one end and a turbo mount on the other end. That means no welding on the CRACK-PRONE EXHAUST MANIFOLD! The idea is a great one, as slant six exhaust manifolds are notorious for cracking, and welding on them only makes the probability more likely to happen.

Pishta gets my vote as "Mopar Man-of-the-year" for coming up with this solution to a very natty problem.

Here's a picture of the J-[ipe in action...
 

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only reason a boost car stops pulling is its running out of fuel, hit a limiter, or the turbo is to small...
 
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