273ci thoughts?

[rumblefish360]

OH, your dislike of he Hyper pistons.... pistons fail for a few reasons. No matter what there made of. You just have to be on your game to start with when you use a Hyper since they will fail quicker when you abuse them/race them. Spark timing & too small of a ring gap are Notorious killers with a hypereutectic piston’s. However, it will do the same to a cast or forged piston. Then It doesn’t matter what the piston is made of. It will take up the whole damn engine.

Below my ‘67 - 318 in reasonable shape. Getting ready for a cam swap, intake and yup! Headers.

 

[ir3333]

Back to the original post.How much power do you want, how much do you want to spend and how are you going to drive your car?
I'm betting you would be best served with a mild 360, economical to buy or build and more than fast enough to be fun. Now, having said that my personal favourite is the 340

 

[66fs]

Sorry 273, I see a lot of mumbo jumbo.
Bottom line, an extra 45 cubes due to bore size will make for a more powerful engine in HP and TQ across the board when otherwise equally equipped. What ever you do to the 273, I get to do to the 318. The 318 wins.


The chances? I’d call it even. And that chance I’d call piss poor. That is a 52 year old engine. I stated that the low compression of the 318 can be fixed by a low dollar head killing which is worth the cost of indeed you “NEED” that extra compression.


You can turn a 318 into a 340 easy?
Oh please due tell! I have yet myself find a 318 able to accept a over boring of .130. Is it possible? I just haven’t seen it.

Now about head flow. I agree. How that enters in the cubic inch engine vs. engine discussion when basically, from where I stand, they use the same head. The particulars of the exact head castings used on the engines throughout there run years and the flow rates of these heads I don’t have known in my head or even bother to keep on paper/lap top/ stone carvings.. LOL!
As I said, “Basically there the same head.”

Do you have a reliable chart that YOU personally flowed? A trusted friend? Some wacko internet source?

Oh, I thought we were having a conversation. If you really think I'd overbore a 318 to 340 specs, you'd be wrong. And if you think.065 of an inch larger radius bore makes any difference in a street engine you'd be wrong. Can you disprove my general flow numbers?

 

[replicaracer43]

Oh, I thought we were having a conversation. If you really think I'd overbore a 318 to 340 specs, you'd be wrong. And if you think.065 of an inch larger radius bore makes any difference in a street engine you'd be wrong. Can you disprove my general flow numbers?

Looking at this from another angle, what is the advantage a 273 has over a 318? I know I have torn lots of 273s down, kept the rocker assembly's and crankshaft, and thrown the rest in the scrap bin. All 2 barrel engines, no commandos

 

[273]

Not trying to be personally critical, 273, so please don't take this to heart as an insult; just trying to work this out. The above is a false argument; the only thing that this says is that the example 340 and 440 engines are equally efficient at the same airflow, which is the case since you picked the flows and power per ci to be equal. It is a meaningless argument as to the effect of displacement.

Real world, the airflow will not be equal at all; we work to make the airflow adequate to support the cubes. So torque/HP output will not be equal vs cubes. A quick look at BB vs SB port flows will tell the story.

Can't agree on the thought that considerations of torque are not important. In some racing forms, it is a far, far better measure of overall performance than peak HP. Peak HP for 4 stoke engines like we typically build here is a convenient and direct indicator of 1/4 mile performance, so is useful as a measure of performance in the drag race world.

The engines we use /6 sb bb and depending on parts selection and preparation the efficiency is gonna very but in a relatively narrow way. It takes a certain amount of fuel within a ballpark range to make "X" HP and since fuel to air ratio can't very greatly its gonna take similar amounts of air flow to make a certain amount of power within a narrow range.

To make the same 500 hp with two engines one twice as large as the other eg. 250 cid vs 500 cid the 250 cid will have to spin twice as many rpm give or take depending on there efficiencies. Which means there are both are consuming about the same amount of fuel and air. 2nd even at the same hp the 500 cid will make ruffly twice the torque but my main point the 250 will need about twice the gear equalling out the torque that the tires see.

Torque is a snapshot of what an engine is doing at one rpm, HP is all those snapshots added together over time "rpm", eg. say for simplicity one engine does 1 rpm and the other does 2 rpm, 1st makes 500 lbs=ft @ 1 rpm an engine 2 makes 250 lbs-ft @ 2 rpm both are doing the same amount of work "hp" but the 2nd engine needs to do it at twice the rpm to accomplish it .

So ya torque is important but so is rpm, neither by itself can tell us much about an engines ability, eg how much torque do i need to do 10's in the quarter mile or how much rpm ? but we know ruffly how much hp.

 

[273]

Not trying to be personally critical, 273, so please don't take this to heart as an insult; just trying to work this out. The above is a false argument; the only thing that this says is that the example 340 and 440 engines are equally efficient at the same airflow, which is the case since you picked the flows and power per ci to be equal. It is a meaningless argument as to the effect of displacement.

Real world, the airflow will not be equal at all; we work to make the airflow adequate to support the cubes. So torque/HP output will not be equal vs cubes. A quick look at BB vs SB port flows will tell the story.

Can't agree on the thought that considerations of torque are not important. In some racing forms, it is a far, far better measure of overall performance than peak HP. Peak HP for 4 stoke engines like we typically build here is a convenient and direct indicator of 1/4 mile performance, so is useful as a measure of performance in the drag race world.

I have no problem with critical, I could even be wrong, I just Don't think so as of now
It wasn't meant to be a real world example, just generally to show how engine size torque gearing rpm are interconnected and two engine of different size but same hp will be putting similar torque to the ground, cause most seem to feel more torque at the crank is an advantage, but think of little about the drivelines gearing and the final the output at the tires.

 

[66fs]

Looking at this from another angle, what is the advantage a 273 has over a 318? I know I have torn lots of 273s down, kept the rocker assembly's and crankshaft, and thrown the rest in the scrap bin. All 2 barrel engines, no commandos

The OP has one. Just wanted a driver. Funny that is what I used to do with 360's Kept the heads and rods and scrapped the rest. I like the best heads on the smallest engine. runs normal and when you want go go fast, just wind it up. More of a sports car driver, anywhere, all day long, kind of guy. V rated 50 series tires, Not a drag racer.

 

[rumblefish360]

Oh, I thought we were having a conversation. If you really think I'd overbore a 318 to 340 specs, you'd be wrong. And if you think.065 of an inch larger radius bore makes any difference in a street engine you'd be wrong. Can you disprove my general flow numbers?

I think I mixed up my thoughts and posts.. LMAO!
Oh yea, two he talks. Talking here, no other way.

On the .065 larger bore making a difference on a street engine, the truth is hard to find unless you clock it or dyno it. It’s there. How it translates in a vehicle is different. The amount of difference’s climb high and quick.

I can prove there is a difference! Wait! Why would I when it’s been published her and over again? What I do have handy though are cylinder head flow sheets from the same head showing the difference between cylinder bore sizes. Though it is far removed from its application in this topic, it does show a difference. I’ll scrape it up later.

From here on, it gets theoretical. As the exact build specs would have to be given and the best anyone could do here short of an actual dyno test between engines is a dyno sim.

It back to the street mention. The old adage is true, bigger is better on power production which I only trumped by a positive displacement pressure additive.
Turbo/super charger.

 

[273]

The old adage is true, bigger is better on power production which I only trumped by a positive displacement pressure additive.
Turbo/super charger.

Like to add RPM, which all basically add displacement over time, mainly measured with CFM.

 

[ir3333]

i know a lifelong racer who has built and raced all the mopar examples...and he wrote a book with his results! It's not hi horsepower or a big torque number ...it's balance in the total package.
He notes in his book that the high horsepower engines he raced never E.T' d well because making hp at hi rpm usually sacrifices lo end torque.
That's why early 340 A bodies did so well with only 275hp and 340 ft. lbs.

 

[273]

i know a lifelong racer who has built and raced all the mopar examples...and he wrote a book with his results! It's not hi horsepower or a big torque number ...it's balance in the total package.
He notes in his book that the high horsepower engines he raced never E.T' d well because making hp at hi rpm usually sacrifices lo end torque.
That's why early 340 A bodies did so well with only 275hp and 340 ft. lbs.

More transmission gears can get away with a narrower powerband thats more peaky, if you had a variable trans that keep an engine at peak hp, then peak would be all that matters.
You divide your powerband into multiple ranges eg. 3000-4000 4000-5000 5000-6000 and figure how much time is spent in each during a run and basically work on them from longest to shortest.

 

[66fs]

I think I mixed up my thoughts and posts.. LMAO!
Oh yea, two he talks. Talking here, no other way.

On the .065 larger bore making a difference on a street engine, the truth is hard to find unless you clock it or dyno it. It’s there. How it translates in a vehicle is different. The amount of difference’s climb high and quick.

I can prove there is a difference! Wait! Why would I when it’s been published her and over again? What I do have handy though are cylinder head flow sheets from the same head showing the difference between cylinder bore sizes. Though it is far removed from its application in this topic, it does show a difference. I’ll scrape it up later.

From here on, it gets theoretical. As the exact build specs would have to be given and the best anyone could do here short of an actual dyno test between engines is a dyno sim.

It back to the street mention. The old adage is true, bigger is better on power production which I only trumped by a positive displacement pressure additive.
Turbo/super charger.

I don't run dyno tests or do bench racing, Sorry. Not into theory. I have built and driven all the above. Flow numbers come from Jason and backed up by other reliable independant sources. You and I will not see eye to eye. I don't use my cars the way you do. As always you are welcome to your opinion. I'll still scrap all the 360's and 318's and keep the 273's and 340's. Because that is what I like.

 

[ir3333]

i have another friend with a 340 dart that always raced his buddy who had a 440 GTX.Both cars were far from stock and they were always making changes to "one up" each other.They hit a point were at the strip the GTX would consistently inch the little 340 out.As a last ditch attempt to slay the gtx he installed a .489 gear set and took the big block out shifting just below 8000.
Next day took the .489's out and never used them again.
..I just love that story!

 

[66fs]

Looking at this from another angle, what is the advantage a 273 has over a 318?

I have had both, the original 273 in my 64 Cuda was always very fast. No other explanation. Faster than factory HP 360's.

 

[replicaracer43]

I have had both, the original 273 in my 64 Cuda was always very fast. No other explanation. Faster than factory HP 360's.

What exactly is "very fast" ?

 

[fishmens67]

I have had both, the original 273 in my 64 Cuda was always very fast. No other explanation. Faster than factory HP 360's.

I bet if you put that factory HP 360, if there ever was one, it would be faster than the 273.
FWIW I never came across a factory Hi po 360. a smog 360 would still be faster. lol

 

[replicaracer43]

I bet if you put that factory HP 360, if there ever was one, it would be faster than the 273.
FWIW I never came across a factory Hi po 360. a smog 360 would still be faster. lol

74 dusters and dart sports had the "hp" 360 engine, as well as the lil red Express trucks in '78 and '79

 

[ir3333]

I didn't think any 360's were Hp? Weren't they standard lo compression engines with the 340 cam and small valve j heads?

 

[rumblefish360]

Like to add RPM, which all basically add displacement over time, mainly measured with CFM.

It’s impossible to add displacement overtime in RPM. What are you talking about his work cycles per second.

 

[273]

It’s impossible to add displacement overtime in RPM. What are you talking about his work cycles per second.

CFM - Cubic Feet per Minute, could use cubic inch per minute just be ridicules sized numbers. Cid x RPM / 3456 = CFM.

No matter which way you slice it, Naturally aspirated, blown, turbo, large displacement, small displacement, high rpm, low rpm etc... is gonna have to displace a certain amount of fuel and air in certain amount of time to make a certain HP, within a given tolerance based on efficiencies. CFM is a "Displacement" of air "Cubic Feet" in time, a "Minute", RPM is based on same time "Revolutions Per Minute". Engines are measured in there static displacement "liters, cubic inch, even cubic feet if you wanted" a working engine ain't static. So a 250 cid at 10,000 rpm is "Displacing" the same amount of air as 500 cid at 5000 rpm given same VE%. so in that minute of time there the same size, same dynamic displacement.

 

[rumblefish360]

I get that. But the engine can not grow in size no matter how you say it. Your just dead wrong no matter how you slice it.

 

[fishmens67]

74 dusters and dart sports had the "hp" 360 engine, as well as the lil red Express trucks in '78 and '79

I know, but I believe it was just a HP badge. more of an embarrassment for Mopar at the time. lol
anyway the 273 was a good engine in the pre 67 a-bodies.

 

[273]

I get that. But the engine can not grow in size no matter how you say it. Your just dead wrong no matter how you slice it.

Never said it grows your engine, just saying dynamic displacement "CFM" matters more in the end than static displacement "CID".

 

[replicaracer43]

I know, but I believe it was just a HP badge. more of an embarrassment for Mopar at the time. lol
anyway the 273 was a good engine in the pre 67 a-bodies.

Not exactly, the "hp" 360s got the windage tray, a hotter cam, stiffer valve springs and a 4 barrel carburetor. And in 1978, was the fastest production vehicle, in a TRUCK no less, sounds like a performance engine to me!

 

[pishta]

E58 or EH1 motor option, a 360 with 340 parts:
Camshaft from the 1968 340 4-bbl.
Red stripe valvesprings with damper from the 1968 340 4-bbl.
Standard valve retainers (replacing rotators)
Large Thermo-Quad from Police 360
Intake manifold from the 1978 Police 360
Windage tray from Police 360
Roller timing chain and sprockets from Police 360
Dual-snorkel air cleaner with fresh air ducts
Chrome valve covers and air cleaner lid
Street-Hemi style mufflers

EH1 (truck) motor didnt have cat's so they had a better exhaust and 255 HP, up from 245 of E58.