Slant Six 170 vs. 225

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The Dart GT

The Dart GT

1963 Dodge Dart GT Convertible
Joined
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So the guy has a dilemma: I remember 39 years-ago when I last drove this car that the original 170 was pretty sluggish (around 100 hp?). I would like just a little more pep. (I'm not trying to turn it into a muscle car).

Does anyone know how much HP is created with the two barrel carb with the two barrel intake on a 170?

My other option is...I have a spare rebuilt 1972 225 that only has about 1,500 miles on it that will get me roughly 145 hp. Will I notice a big difference with the extra 45 hp? Obviously a lot more work to do the engine swap.

I don't remember if I had any work done on the 170. I know it never used any oil and the odometer says 165k.

Opinions? Thoughts? You guys are great. Thanks
 
Unless you upgrade the exhaust, as in headers, or at least opening up the exhaust manifold outlet to 2.25" or 2.5", you'll not see much of a difference at all. If you put more in, you need to be able to get more out and the stock 1 7/8 exhaust pipe ain't gonna get it done.

Also, while a decent article, that article up there ^^^^ is way biased towards its sponsors. Even doing everything they did, you ain't gonna see a 77hp increase still naturally aspirated. 50-55, I could see.
 
I would venture to say that if you aren’t racing, and even IF both engines were the same HP, that the 225 would offer more torque where you would really need it- on the street accelerating from a stop.
As said, open up the exhaust. But please don’t run duals. If you are one that believes you need to see 2 tips, split a good free flowing single system.
 
RogerRamRod said:
I would venture to say that if you aren’t racing, and even IF both engines were the same HP, that the 225 would offer more torque where you would really need it- on the street accelerating from a stop.
As said, open up the exhaust. But please don’t run duals. If you are one that believes you need to see 2 tips, split a good free flowing single system.
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Good point about the torque. Hadn't thought about that. Don't worry. No dual exhaust.
 
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RustyRatRod said:
Unless you upgrade the exhaust, as in headers, or at least opening up the exhaust manifold outlet to 2.25" or 2.5", you'll not see much of a difference at all. If you put more in, you need to be able to get more out and the stock 1 7/8 exhaust pipe ain't gonna get it done.

Also, while a decent article, that article up there ^^^^ is way biased towards its sponsors. Even doing everything they did, you ain't gonna see a 77hp increase still naturally aspirated. 50-55, I could see.
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I was already going to upgrade the exhaust pipes to a larger diameter. Good point. But....how does one go about increasing the diameter of the exhaust manifold?
 
The Dart GT said:
I was already going to upgrade the exhaust pipes to a larger diameter. Good point. But....how does one go about increasing the diameter of the exhaust manifold?
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Here's what I did. I have a good friend right down the road who is an excellent fabricator. I suck at it. I'd probably grind everything BUT what I needed to. lol
Exhaust Manifold Mod
Just installing the bigger pipe really does nothing since the exhaust still has to come through that tiny manifold outlet. It made a noticeable difference on my stock 170 in my Valiant even before I added the bigger pipe. Of course now I have a pretty warm 225 in it.
 
The Dart GT said:
Good pint about the torque. Hadn't thought about that. Don't worry. No dual exhaust.
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It's a trade off. The 225 is 55 more cubes. However, it has a really long (4.125") stroke. So in the rev department, the 170 has it beat. The short stroke allows the 170 to rev quicker. We have members here who race the 170 in different forms with good success. None of the slant sixes will ever be a V8, but they are a lot of fun. @Charrlie_S is really famous in the slant 6 world and has raced them for years. Maybe he will chime in, since I tagged him. He can further help dissect the differences.
 
Just adding a 2 bbl to the 170, will not get you a lot, but doesn't take a lot, either. Are you running a standard trans, or an automatic. Putting a 72 engine in front of a 63 trans, has some issues.
Personally, if it were me, and the 170 was in good condition, I would mill the head, to get a true (about) 8.5-1 CR, add the 2 bbl, and open up the exhaust (single). If you want to spend a little more money, a mild cam, and consider (optional) a little bowl porting, and back cut the valves (while the head is off). The rest is tuning.
PS: Convert to electronic ign. I like the GM HEI conversion, or the pertronics. Not a fan of the Mopar system.
 
Question, when was the first un-leaded head made? I have 5- /6s and thinking hard on using one in my 69 notch.
 
Ceedawg said:
Question, when was the first un-leaded head made? I have 5- /6s and thinking hard on using one in my 69 notch.
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I'm not positive. But what difference does it make? If you're swapping heads, any way, you should do a valve job on the head. The factory hardened seats are only a few thousands deep, and a valve job removes the hardened surface. I would suggest installing hardened exhaust seats during the valve job, if you're looking for longevity.
 
Charrlie_S said:
Just adding a 2 bbl to the 170, will not get you a lot, but doesn't take a lot, either. Are you running a standard trans, or an automatic. Putting a 72 engine in front of a 63 trans, has some issues.
Personally, if it were me, and the 170 was in good condition, I would mill the head, to get a true (about) 8.5-1 CR, add the 2 bbl, and open up the exhaust (single). If you want to spend a little more money, a mild cam, and consider (optional) a little bowl porting, and back cut the valves (while the head is off). The rest is tuning.
PS: Convert to electronic ign. I like the GM HEI conversion, or the pertronics. Not a fan of the Mopar system.
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Thanks Charlie! Kitty was just askin about you the other day. You been doin ok?
 
Ceedawg said:
Question, when was the first un-leaded head made? I have 5- /6s and thinking hard on using one in my 69 notch.
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1972, I believe was the first full year. Like Charlie says though, they are only induction (heat) hardened and it does not go very deep. Chances are after the first valve job, it's gone and possibly before, if it's a high mileage engine.....and most are.
 
Charrlie_S said:
Just adding a 2 bbl to the 170, will not get you a lot, but doesn't take a lot, either. Are you running a standard trans, or an automatic. Putting a 72 engine in front of a 63 trans, has some issues.
Personally, if it were me, and the 170 was in good condition, I would mill the head, to get a true (about) 8.5-1 CR, add the 2 bbl, and open up the exhaust (single). If you want to spend a little more money, a mild cam, and consider (optional) a little bowl porting, and back cut the valves (while the head is off). The rest is tuning.
PS: Convert to electronic ign. I like the GM HEI conversion, or the pertronics. Not a fan of the Mopar system.
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Forgot about the Pertronic, was going to go to the electronic one.
 
Charrlie_S said:
More money, more weight, zero gain over a larger dia free flowing single, in the rpm range of a street driver.
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Also, from my understanding, better scavenging. You’re only getting an exhaust pulse every 120° of rotation, so its not like 2 Cyl worth of spent gas is fighting for the same space. (Yes of course the same is true for 8cyl)
Plus IMO, tru full duals on pretty much any 6 (at least any I’ve heard) sounds like pure ***. And Im not hatin, I like me some in-line 6s, I’ve owned a few slants, Fords, & Jeep 4.0s. There’s also reasons BMW kept at it for so long.
 
RogerRamRod said:
Also, from my understanding, better scavenging. You’re only getting an exhaust pulse every 120° of rotation, so its not like 2 Cyl worth of spent gas is fighting for the same space. (Yes of course the same is true for 8cyl)
Plus IMO, tru full duals on pretty much any 6 (at least any I’ve heard) sounds like pure ***. And Im not hatin, I like me some in-line 6s, I’ve owned a few slants, Fords, & Jeep 4.0s. There’s also reasons BMW kept at it for so long.
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That's right. The slant 6 responds much better to a well thought out single exhaust. Especially when using headers. Because of the firing order, the exhaust pulses are swapping between the first three and the last three every time the engine fires and that's perfect for scavenging. People put duals on them and I believe they lose a little when doing that.
 
I’ll defer to the guys that build these every time, I only drove pretty much stock stuff, but….
An engine that felt sluggish 39 years ago with 145K (100hp- new rating?)
Vs
An engine with 1500 miles and 145hp.

of course this all depends on how accurate those power numbers are (or were), but the question being; would you feel 45 hp, I would say…You’re damn skippy your gonna feel 45hp, thats almost 50% more. Would you feel 45 hp if you were at 500 hp, probably not. I’d even wager to say that at 500, you’d be hard pressed to notice a 50% increase (unless of course you were racing) but at that point you’d be so far over what a 63 dart needs to drive around, that you’d never be making use of what you had already.
BUT, points to ponder;
1) originality
2) “a little more pep. (I'm not trying to turn it into a muscle car).”
3) how much do you want to spend for that little more pep & how much will you get comparing dollar for dollar what you will spend on those 2 alternatives?
 
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I'll tell you when I am happy with a slant 6. When I can pull a hill without down shifting. When I have enough nads to actually accelerate going uphill without down shifting, with Kitty in the passenger's seat and a full load of groceries in the trunk and I have that now. By a LOT. Makes me grin.
 
Went to the offenhauser intake, avs2 500 4 barrel, clifford headers (3-2-1 design) and 2.25" exhaust on an otherwise stock 225 and it easily buries the speedo and keeps going on a 64 Dart 2 door. Not a real cheap upgrade though
 
RustyRatRod said:
I'll tell you when I am happy with a slant 6. When I can pull a hill without down shifting. When I have enough nads to actually accelerate going uphill without down shifting, with Kitty in the passenger's seat and a full load of groceries in the trunk and I have that now. By a LOT. Makes me grin.
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And good gas millage
 
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