Difference between 360,340 and 318

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Coyote Jack

Coyote Jack

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I am just wondering what kind of HP and TQ differences I would get between each of the small blocks. We will say that the boost will be supplied by a 6-71 type of blower and be limited to 8 lbs. Everything else on the engines would be the same, ie: heads, cam, compression ratio, exhaust, carbs and ignition. compression would be 8 to 1.

Jack
 
The 360 has a longer stroke than the 318 or 340. The 360 stroke is 3.58" and the 318/340 stroke is 3.31". With everything being equal the 360 should produce more torque than the other 2.
 
That's what a mopar mechanic told me when I built mine. Around town a 360 will beat a 340 because of the torque, at the drag strip the 340 revs high easier.
 
I don't think you are going to see a lot of difference between the three with a blower. Superchargers add lots of torque through out the power band.
 
I hear this nonsense--and nonsense is exactly what it is, about how a 340 "revs easier."

Horsepower and torque are just that--and an engine that develops more HP at lower RPM is better off, all other things being equal. Secondly, "revs easier" is pretty much limited by the heads and valve train--and it turns out that nowadays there are a lot better heads than could be had for the 340 "when built."

What I'm trying to say, is, if an engine puts out 2 hp, it's not going to "rev easier" no matter what the stroke is--it's the load on the engine---gearing and weight of the car--that determines "how fast" the damn thing revs, not the stroke.

To put it another way, if you could build a 340 and a 360 with absolutely identical output, they would both "rev the same" and in the same car with the same gearing, would be turning EXACTLY the same RPM at the end of the 1/4

Now don't get me wrong--there ARE advantages and disadvantages to different bore/ stroke combinations TO PRODUCE POWER. People like Jenkins proved that a long time ago. Nobody had ever heard of a "383 Chivvy" until Grumpy came up with it.

I guess to boil this all down, what I'm saying is, forget RPM and concentrate on the power you can produce. The only reason to try to get power out of a little bitty engine is IF YOU HAVE CLASS RESTRICTIONS, or are limited by budget, the 'ol "run whut ya brung."
 
Burntorange70 said:
I don't think you are going to see a lot of difference between the three with a blower. Superchargers add lots of torque through out the power band.
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You are on the right track as far as my question is concerned. I am wondering what the numbers would be when each of these engines have a blower on them.

To the other guy's, thanks for your answers but I think you were missing my question. I have a pretty good idea what the differences are for each of the engines before a blower is set on top. It's what happens after a blower is added that I'm looking for.

Jack
 
Burntorange70 said:
I don't know about easier but short stroke = quicker revs.
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It revs quicker in neutral, but how about with a load on it?

They don't award trophies for how quickly an engine will rev in neutral....

A 360 has more torque than a similar-build 340, and will excel at accellerating X number of pounds due to the longer stroke and having more cubic inches.

You'll notice, I said "similar build." Race 340s with W-9 heads and 14-1 compression are apples-oranges compared to a street 360.
 
Here it is: The Answer

The 318 will do it all, get the T-shirt and The short block will be cheaper to replace !!!!
 
Prine is right. A comparably build 318 will produce plenty of power. I stuck with the 5.2 in my duster because I can pick up another one complete anywhere from $3-500 off craigslist.
 
Prine and TT'74,

Thanks for the answers. I was thinking that way but just wasn't sure. I have a 318 sitting in my garage that has a forged crank. That will help keep the build on budget. Also will make it easier to get good pistons from what I have seen on the manufacturers sites. A good set of heads, (maybe used eddy's) and a set of rods and I should be good to go.

Jack
 
Coyote Jack said:
Don't be sorry. You were on the right track as far as what info I was looking for.

Jack
Click to expand...

Was just trying not to get off topic about revs. LOL

Will ask my dad when I see him next. He is having a whipplecharger put on his motor and has done a lot of reserch on things like this.

Rely you are only looking at 42 cubs difference 318 VS 360. Don't know that it would make a lot of difference when you go putting on a blower that tricks the motor in to thinking it is bigger than it rely is.
 
318 has smaller main caps, and weaker rods if we are talking stock blocks with stock parts, the 340 starts out with better rods, stronger caps and a forged crank, 360's are cast, some of the early 318's are forged also. if its low HP they will all hold up, if high hp then the 340 in stock form is better. for those in love with the 318 they are great motors but in a high hp build i would want the better rods and thicker webs and caps on the 340.
 
Assuming all motors are built similar lets say to the 1 HP to CI level you gain about 40 hp with the 360 over the 318. Hard to beat cubic inches. Your going to see about a 50% increase in HP with 8 pounds of boost so 318 around 477 HP and 360 around 540. On the track with slicks and good tuning on each combo the 360 would be quicker. On the street running legal tires I bet you wouldn't notice much difference. With those kind of power levels in a light A body your going to be traction limited.
 
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