What's so good about the 340!

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hux340

hux340

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G'day All,
Have a 71 Demon 340. Have never owned an American Muscle Car let alone a Mopar before as I've always bought Aussie muscle stuff. This is the first USA car I've bought. In saying that very bloody impressed with the performance of this 340 motor! It's not stock, (has only about 3k on it), but it does have a bit of a cam, but no way full on.
Question - why were they such a killer engine?
I go cruising & when I'm in 1/2/3rd at about 3k & I gun it the thing just launches with this induction roar. Brings a massive grin to my face & all who are with me in the car when I do it.
Love it, great car.
 
Tell us your combination, no way in hell, is it stock. As for the roar," Thermoquad"..? comes to mind...And no way in bloody hell,is that a bad thing ,mate.. You must have paid a pretty penny ,to get it there.
In theory: the best small block Mopar ever assembled, off the assembly line.. The engineers ,did a fantastic job: Good quench, good factory(X cylinder heads..) unported heads( they flow 220 cfm @ .500 lift, in current terms..)great stock intake /exhaust manifolds..Cam timing was decent..(that first '68 340 stick cam, was nasty..).. 71 Thermoquad intake, was the best setup, if you know how to tune it.. Added my historical references: Again , what do you have?..., & your car??( lol..)
 
For those of you young whipper snappers I was there at the drags with my dad in 68-69 when the funnest thing was running pure stock races. Had to run with street tires, closed headers etc. The 340 cars were very tough to beat if they had any kind of gears. They would pull several car lengths on the big block cars from the start and hang on at the end.
We had a 69 Cuda Formula S, automatic car with 3:55 gears. That little pure stock with tires was good for mid 14's in COLORADO. 5,280 feet high. Always felt the 340 cars were possessed.
 
340's were never built for anything but muscle cars

They were not in the land barges ( c bodies) or trucks, just in go fast cars

The also had good stuff inside

Windage tray, double row timing chain, great heads intake and exhaust manifolds

In the light weight a bodies made a package hard to beat

NHRA looked at the factory hp rating, after they were wiping up the tracks across the country instead on a 275 hp factor they said more like 315.

You have a good combination in body style and weight to hp ratio

Enjoy your American Muscle!
 
340's where blessed with high flowing heads with 18 degree valves and big bores which all adds up to an engine that can flow a lot of cfm's (horsepower) and the intake/exhaust was no slouch either . 2nd the 340 had great bore stroke and rod ratios to add to that advantage of the great top end. Weakest part was probably the cam not saying the stock cam sucks but leaves a lot of power on the table.
 
They were way over built from factory. when my chevy buddies used to build a small block it was "gotta upgrade to 3/8 rod bolts, pink rods, need screw in rocker studs, need a double roller timing chain, need a windage tray, etc" Mopar guys be like, Hmm got that already!
 
hux340 said:
G'day All,
Have a 71 Demon 340. Have never owned an American Muscle Car let alone a Mopar before as I've always bought Aussie muscle stuff. This is the first USA car I've bought. In saying that very bloody impressed with the performance of this 340 motor! It's not stock, (has only about 3k on it), but it does have a bit of a cam, but no way full on.
Question - why were they such a killer engine?
I go cruising & when I'm in 1/2/3rd at about 3k & I gun it the thing just launches with this induction roar. Brings a massive grin to my face & all who are with me in the car when I do it.
Love it, great car.
Click to expand...

You answered your own question!
 
340 engines were factory power engines. They were built to be street fighters, and they sold a lot because of it. The only reason I like the 340 though is it's historical name plate. If someone offered me a worn out 340 and a worn out 360 I would probably go after the 360. 360s are plentiful and they have tons of power potential. For me it's like buying between gibson and epiphone. Epiphone guitars are made to the exact same spec as gibson guitars, they just don't say gibson. Same guitar for half the price. If you want the 340 you pay for it. Just my opinion.
 
In addition to what has already been said about the internals, the early 340s also had (from the factory): forged crank, forged pistons and floating piston/rod pins.
The 4.040" bore and 3.31" stroke let them rev quick.
It was so much fun to pick on a big-block car on the street. The 340-powered A-body would always jump out to a quick lead - and street races are always short so the big blocks never had a chance to get into their power.
 
jay soneff said:
For those of you young whipper snappers I was there at the drags with my dad in 68-69 when the funnest thing was running pure stock races. Had to run with street tires, closed headers etc. The 340 cars were very tough to beat if they had any kind of gears. They would pull several car lengths on the big block cars from the start and hang on at the end.
We had a 69 Cuda Formula S, automatic car with 3:55 gears. That little pure stock with tires was good for mid 14's in COLORADO. 5,280 feet high. Always felt the 340 cars were possessed.
Click to expand...


Jay, I used to run G/Pure Stock at OCIR with my '69 340 Swinger. "Pure Stock" there meant no headers.
My best was a 14.28 @ 98+mph with 3.23 non-suregrip gears, a 727, and rock-hard Polyglas tires. Trophied numerous times.
 
My 340 internals all forged. 1.6 rockers. J heads redone 2.02 in. 1.65 ex. Solid lifter cam .550 lift on both valves. Dougs headers. Six pack for carb. Motor is in a 67 fb barracuda. Why a 340? For the simple reason I know how to work and modify them. I can spin this motor to 6500 Rpm all day long. Internally balance. Hear is a hint. The old 273 motors had forged cranks in them. Don't throw that motor away till you get the crank. Some even had 1.5 adj. rockers, grab them to.
 

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The 340 was engineered for performance, which forfeits some life span. This was a huge step away from what Dodge Brothers had built their reputation on. It was what the market wanted. Today the majority of 340 blocks have been bored and bored again.
 
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