Hey , what did they do to the motors as they got into the 1970s that dropped the HP

such as

a 1967 slant is rated at about 145 hp

while a 1974 slant is rated at about 110 hp


Did they just put a smaller carb on it ?

Or was it smaller valves in the head?


What I'm getting at is ....

does a 74 motor block have the same hp potential as say a 67 block.

after rebuilding my head my bottom end has gone out and I'm looking at just swapping it out for another motor, but all I can find so far are 70s blocks.

I'm thinking that theres no differance....?

right , wrong ? ?

answers please

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'67 Dart 225 Super Six

In 1972 the 'system' went to SAE net measurements over 'Brake' measurements...

The old system was like your slant, not accessories or belts on an engine dyno (figures at the crank), net was supposed to be more accurate with a full load of accessories (A/C on, load on alternator), and supposedly they took the measurements from measurement on a chassis dyno.


The 1967 block is all the same as the 1974 block...but a few things happened:

The 1967 motor will have a baby Holley 1920 on it, not the bigger mouth gaping Holley 1945.
The 1967 stock cam is a bit 'smaller' than the 1974 stock cam.
The 1974 head would have hardened seats for unleaded gas, and better combustion chambers (you won't notice much driving an automatic to the grocery store...)


For rebuilding, you can grab any forged crank 225 up to 1976 and swap your 1967 crank into it...

-D.Idiot

The later Net Horsepower ratings were not made using chassis dynamometers, but they do include factors for parasitic losses - water pumps, etc. - that were not addressed under the Gross Horsepower rating.
Not that there has recently been another change in the rating systems, one that cost several advertised horsepower for several cars - but added a few to some!

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"When you find a big kettle of crazy, it's best not to stir it." - Pointy-haired Boss

1964 Valiant V200, 225/Pushbutton 904
BBD, CAI, HEI, LBP, AC, AM/FM/USB, EIEIO

Yep, and the SAE Net numbers, for any given level of engine power, are lower than the old SAE Gross ("BHP") numbers. That accounts for most of the difference between the '71 and '72 ratings.
There were multiple venturi sizes and two throttle bore sizes for the Holley 1920 and Carter BBS carbs used in '67. Multiple venturi sizes and only one throttle bore size for the Holley 1945. In no case is the Holley 1945 bigger than the 1920 or BBS.
The combustion chamber improvement was introduced for the 1967 model year and was the same as in 1974. The primary main effect of this change was not on horsepower, but on emissions.

Aside from the rating system change giving lower numbers, the rest of the differences in pre-'72 and post-'72 engine ratings are due to the progressive introduction of stricter and stricter emission standards in North America, and the half-baked measures taken to comply with them with the slant-6. EGR, then more EGR, then even more EGR. Lower compression, then even lower compression. Smaller and leaner carburetors. Shorter and slower advance curves. Hotter running. More restrictive multiple-catalyst exhaust systems. Still with the same old stone-age combustion chamber! Had they not dropped the late-'70s program to produce an aluminum fast-burn cylinder head for the slant, the poor old 225 might not have been down to 80 pathetic, gasping, wheezing horsepower in its last few years.

Back to the question of ratings: I have a hard time placing much stock in the factory ratings year to year. Consider: The 225's published rating remained at 145bhp, 215 lb-ft of torque, at the same RPMs, from 1960 through 1971. That's across three different camshafts, multiple different ignition advance curves, and a lot of markedly different carburetors. The only change in ratings during this whole time was in '67 when the 170's published rating was changed from 101bhp to 115bhp, correlating with the installation of the larger 225-sized carburetor (1-11/16" throttle bore) and the 240°-236°-16°-0.395" cam that had been installed in the 225 for '65.

Other ratings of interest: 160bhp for the export 2bbl setup of '67-'76, and 180bhp for the Argentine twin 1bbl setup.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

wow you really know your stuff

You said that they began to progressively drop the compression as went thought the seventies.

HOw was this achieved?

Did they fatten up the head or the block?

And what would it take to get a 74 electronic distributator to perform like say a 67 one. Change the springs?

thanks

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'67 Dart 225 Super Six

You don't want the '74 distributor to perform line a '67 - points vs. electronic - but you could benefit from giving it a better advance curve. Springs are part of it, but so are the weights and slots, as well as the vacuum canister. A search of the forum will give you several hits, including these:
http://www.dutra.org/doug/draft-webpage ... ibutor.htm
http://www.slantsix.org/forum/viewtopic ... ht=recurve

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"When you find a big kettle of crazy, it's best not to stir it." - Pointy-haired Boss

1964 Valiant V200, 225/Pushbutton 904
BBD, CAI, HEI, LBP, AC, AM/FM/USB, EIEIO

linky no worky....

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

I edited it. Two links got stuck together. Had to spray them with the garden hose to get them apart.
Try again.

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"When you find a big kettle of crazy, it's best not to stir it." - Pointy-haired Boss

1964 Valiant V200, 225/Pushbutton 904
BBD, CAI, HEI, LBP, AC, AM/FM/USB, EIEIO

Here's a thread I did on recurving my 64


http://www.slantsix.org/forum/viewtopic ... ight=curve

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

Hey Ed, that's some SWEEEEET steering you got on the valiant there...is that like 15 turns lock-lock? btw where in s.cal are you? I'm heading down in a few weeks to Claremont/Pomona area

Mostly with the head. It's possible/likely the block deck height might've been increased in the late-'70s/early-mid-'80s blocks, but I don't have specifics.
See other responses—yes, you'd change the advance mechanisms. Be advised that if your '67 advance curve is set up and working well for you, it can without too much difficulty be transferred to the '74 distributor (both early and late vacuum advances fit late distributors, springs also interchange). Then the only thing you'd have to match up would be the centrifugal advance slots.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

No, only 10 turns.


I'm right next to LAX, but I'll be out of town for the next couple of weeks.......

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

Yea, I've been chuckling at that, too. It does hit pretty close to home. My arms feel like a windmill when I'm parking the little '64. Gotta keep it rolling slightly, to avoid the futility of trying to swivel a tire on dry pavement.

- 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.

I just make sure I keep my thumbs out of the way when I release the steering wheel to let it unwind.............

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