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  #1  
Old 02-27-2001, 11:19 PM
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Mr.Mopar Mr.Mopar is offline
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Question

I would like some opinions from you guys about rebuilding the 340 that is presently in my Dart, or maybe going with a 360. I know the 360 delivers more torque, but will it out run the 340? Lets say that they both will be built using the same 9.5:1 compression ratio, same 280 Mopar cam and ported 2.02 heads. Which do you think will win the 1/4 mile drag? Thanks in advance for your thoughts.
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Old 02-28-2001, 01:23 AM
70AARCuda 70AARCuda is offline
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Default easy answer

given everything is the same except for the size of the engine.....the 360 will win...cause size matters....lol
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Old 02-28-2001, 01:36 AM
bubby440 bubby440 is offline
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i made a rough draft on my engine analyzer from what info you gave - only 2 hp diff. - 18 ft. lb. torque - both favoring the 360. but if you already have a 340, i would use it.
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Old 02-28-2001, 01:41 AM
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JVMopar JVMopar is offline
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The HP numbers may be higher for the 360. But you have to take into consideration the greater wight of rotating mass in the 360. By using the short stroke 340 (stroke is 3.31") your motor will wind up faster. So you will reach your HP faster. In my opinion I think that I would run the 340. Since the 340 was designed as an all out performance motor. Where as the 360 started it's life as a smogger. That's just my .02.
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Old 02-28-2001, 02:23 AM
70AARCuda 70AARCuda is offline
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Default torque..........

the longer stroke of the 360 will produce more low end and midrange torque......

the 360 has a lighter piston due to shorter compression height and smaller bore...

I have raced both 340s and 360s...everything being equal.....the 360 will win....

tony
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Old 02-28-2001, 09:42 AM
Sly Fox Sly Fox is offline
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I would think the 360 would get off the line quicker than the 340 because of the torque. The 340 would have to play catch up a little bit. I think the 360 would probably be a little bit quicker. But, they are so close that I don't think it would really matter. It's your choice.

Sly
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Old 02-28-2001, 10:40 AM
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You have to factor in the added cost of converting to the 360. You would need the B&M flex plate or a re-weighterd converter. You would also need a different oil pan for the 360. Just something to think about.
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Old 02-28-2001, 08:15 PM
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Smile 340 rebuild

Thanks for your input everyone, you all have very valid points. I loaded the values into a desktop dyno that I borrowed from a friend of mine last night and it does show a small increase in HP and Torque in the 360. I really like the way the 340 winds up and performs and there is a certain amount of prestige that comes with the ownership of a 340 muscle motor. The 360 may win by a small margin, but I think I will rebuild the 340 as some of you mentioned and tweak it a bit more just to make sure I get the extra edge that I need. I would like to say that this is a great forum for posting questions and answers and I credit all of you out there for your expert opinions.
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  #9  
Old 02-28-2001, 11:45 PM
shannon shannon is offline
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No dout that the 360 is going to make more torque. However, while the long stroke 360 is going to have more power down low, the short stroke 340 is going to have a fatter power band up top. Maybe not more power but it will hold more hp longer, where as the 360 would drop off more quickly. I know that we are talking about engines here but think about it, you would have to use a long wrench to break a bolt, but once you break it, do you keep you hand at the long end of the wrench. Probably not, once you get the bolt started, you move your hand lower on the wrench. A short stroke is going to tune better to a higher rpm. The 340 also has a better rod ratio, which really starts to show up around 6000 rpm. Less friction due to the side loading of the piston against the bore. Also the rod and piston do not have to travel as far with a short stroke engine. This is what you want with a high rpm engine. Anyway, for a street car with street gears, the 360 would be the better engine, but with a light car with low gears, I'd pick the 340.
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Old 03-01-2001, 08:54 PM
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rumblefish360 rumblefish360 is offline
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The 360, in thery <SP> ouch> should win. More torque down low with a quicker peak in HP. Even though the 340 has less rotating mass and shorter stoke for quicker revs.
All things being equal and mad sci. aside...of course.
I agree with "Build the 340, because you allready have it"
JVMOPAR:

The 360 did not start life as a smogger really. "72 wasn't really that bad at all. Low compression was the worst thing. Smaller cams and valves are next. Converting the 360 up to 340 levels is the same as doing an eng. for serious street/stip action. All things changed out for better ones. The 340 does offer the advantage of allready having the 2.02's and higher compresion in the early years though.
If were gonna do it on a higher level, New intake , cam, valves carb, pistons etc... Its a tie.
I guess its all in the wallet. And where ya want to go.
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Old 03-01-2001, 09:24 PM
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Cool ONE MORE ?

Are you using a 4- speed, if so i prefer a 340-RPM advantage------auto. would be the 360-torque advantage----70 or older 340 is the choice since they have a steel crank and all 340 had full floating wrist pins--but either engine would benifit from using the magnum head and rollers--dont mess up like i did on my first 340 re-build, replace the factory oil pump drive with a hp unit--i twisted mine @ high rpm's and lifted it outa the pump. lol killed that 340
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