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1977 W-200 318-727-203
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Discussion Starter · #1 ·
Just a brainspin,

In the years '71/'72 or there about engines developed about 200/250 HP from a 318, while later on (emissions) in about '76/'77 they only had 150HP from a 318.

since I only have access to '76/'77 318 engines, I wonder if it's possible to use '71/'72 parts in the '76/'77 castings, and if so, which parts would I need to get the '71/'72 HP's?

 

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crank/rods all the same , pistons dropped compression = lower hp .
 

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Most of the difference, is due to a change in the way horsepower was measured across the board, I think it was 1971 or 72. You will see about the same drop between all the US companies at that time. Then as more emissions came into play, the HP numbers dropped even more.

Keep in mind, pre unleaded fuel heads do not play well with unleaded fuel.
 

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Discussion Starter · #4 ·
SuperBurban said:
Most of the difference, is due to a change in the way horsepower was measured across the board, I think it was 1971 or 72. You will see about the same drop between all the US companies at that time. Then as more emissions came into play, the HP numbers dropped even more.

Keep in mind, pre unleaded fuel heads do not play well with unleaded fuel.
The way I read this, is that the engine itself almost stays the same , it's more the way of measuring the output, that lowers the different HP's over the years???
While others speak about lowering compression by means of the pistons?
And I guess a different cam as well?

So, Imagine I find '71/'72 pistons and a crank for a 318, and I mount them in the '77 block, would that mean that I have an engine with '71/'72 output?

could it be that simple?
 

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SuperBurban said:
Most of the difference, is due to a change in the way horsepower was measured across the board, I think it was 1971 or 72. You will see about the same drop between all the US companies at that time. Then as more emissions came into play, the HP numbers dropped even more.

Keep in mind, pre unleaded fuel heads do not play well with unleaded fuel.
Agreed, Brake HP also known in the US as SAE Gross HP, was used up through the '71 model year. In '72 we went to the SAE Net HP standard. Gross HP was just the engine with no accessories, Net HP is with the waterpump, and other belt drive accessories for that year and model engine as well as whatever emissions and exhaust systems that were used for that engine option. In addition, the "gas crunch", rising insurance premiums on big cubic inch engines and high HP levels as well as ever increasing emissions requirements all conspired to lower HP ratings from the "golden years" of the muscle car era.

Other changes was the swap to hardened exhaust valve seats for use with unleaded gasoline. Swapping parts does not always mean you will get a particular result. If you built an engine to '71 specs, it should put out the same as an engine in '71 would, though the '72 engine is likely identical and just has the different measurement standard. In reality, there were not very many changes made to 318 engines in the '70s and you would have to go back to '69 or so and the car lines to get any really good parts, and they might not be compatible with some of the '70s era parts. And it's all pretty moot considering how much better the Magnum engines were in relation to the old engines anyway so for better small block parts I would look at newer engines, not older.
 

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area51 said:
The way I read this, is that the engine itself almost stays the same , it's more the way of measuring the output, that lowers the different HP's over the years???
While others speak about lowering compression by means of the pistons?
And I guess a different cam as well?

So, Imagine I find '71/'72 pistons and a crank for a 318, and I mount them in the '77 block, would that mean that I have an engine with '71/'72 output?

could it be that simple?
As Elwenil says, it was just a way of calculating the HP. Parts are the same, or so close, its not worth trying to hunt them down.

Me, the number one choice would be to scarf up a 360 magnum, swap the intake to run a 4bbl, and run with it.

Next choice would be a 318 magnum.

I realize those may be hard for you. But when you start factoring in machine shop time, it may look better.

I am not the goto guy for performance. So hopefully some others will chip in. I would look at new pistons, to up the compression a bit. maybe a cam, and 4bbl intake and carb.

Or just freshen up what you have, and run the wheels off it. One of the things that makes the 318 so bullet proof, is that the block is not pushed to get the higher HP numbers. Power is not everything.

First step is to get the heads off, and check them, and the block surfaces for flatness. After that, it becomes a cost/ benefit comparisons, and decide which way you want to go. The more research, and comparisons you do before you pull the plug and decide on a direction, the happier you will be in the end.
 

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Discussion Starter · #7 ·
Great, I'm very happy with this response.
To me it's like a base line, I always thought that it was due to the petrol crisis that mfg.drastically changed the HP output by changing parts in those engines.
I also never realised that those Magnum engines are so much better?

That might also be a big plus, since I remarked that I had difficulty in goiing up a hill with my trailer attached lately, though knowing now what I know, (having headgasket and valve problems) it might also be the reason why it didn't pull as well as I was used to.

but then, where are laying the qualities of such a Magnum engine? are they having more Hp from the same displacement? or more torque?

And is that out of the same number of gallon of fuel? (so efficiency is better), or does the fuelconsumption augment as well?
 

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A '77 318 2 BBL would have had about 145 HP new, a mid '90s Magnum 5.2L (318) would have had 230 HP.  The increase is mainly due to the head design, roller camshaft and multiport EFI.  The block and bottom end is basically the same design with a few small details changed.
 

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Discussion Starter · #9 ·
Great!, if I was to put such a engine in my old Dodge, and replaced the efi for a carb., what effect would that have?
 

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they usta have higher compression and different cams , by 77 the compression dropped , and cams were different due to emissions requirements , with the advent of computers to controll spark fuel mixture , they again upped the compression ( fuel injected magnum engines )
  soo 2 things happened 1 they measured horsepower output differently and came up with different numbers from the same engine , and emissions requirement got stricter  compression dropped cam grind /timing changed .

if you install a magnum engine with a carburetor instead of the fuel injection , basically all your doing is upping the compression and changing the cam , so a retro cam say 1969 340 , and higher compression will make a better 318, yes the mag heads may be better , but they DO crack ..  and so does the magnum block .. ( seen that in places I'd NEVER seen an L/A block crack )  the crank is the same rods the same block dezign the same where it makes a difference ... ( a new casting same dimensions ? )  I'd not worry over unleaded leaded fuel and hardened /non hardened seats .... amaco high test was allways non leaded .... 
 

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Hard to say. It would probably do pretty well. I do know the 300 HP 360 Magnum crate engine Mopar Performance used to sell was just a production 360 truck engine with a dual plane intake. It was rated at that with a 750 CFM carb, electronic ignition and headers.



For the record, the Magnum block is just a slightly altered LA series block.
 

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Dual plan intakes will have the inlet where the carb mounts divided into left and right sides, a single plane will only have one large hole under the carb.
 

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Discussion Starter · #14 ·
Hmmm, I have one with four holes, and underneath one big space that goes to the 4 intake runs???
ment for a 4bbl, it has the partno;2465726.
 

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That is an early, dual plane, 273 intake.  I doubt you will find any stock single plane small block intakes.  I would not use that intake on anything newer, it most likely will have very small runners and wouldn't be much a performance increase when compared to an aftermarket aluminum intake.  I would look at one of those or a stock 360 4BBL truck intake.  The 273 intake is probably worth more as a restoration part for someone working on a '65 Barracuda or similar anyway.
 

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mopar changed heads several times over the years, the 69-71ish engines had smaller chamber heads, which would mean more compression ratio.
also I have seen more than a few stock single plane 318 intakes from around the same time frame. I know that the 318 in my brother's 68 charger was a single plane 2 bbl.   
 
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