340's Rule, 360's Drool !!

I would love to see someone bolt a bone stock hi-po 340 on a dyno with an air gap intake and TTI headers, then strap an air gap on a 360 magnum and the same TTI headers and watch the 360 make more power at EVERY RPM.

The 73 340 VS 74 360 is also a great example, when outfitted the same way the 360 puts the hurting on it real bad.

Also the 360 mag has a stronger block and a hydro roller cam you can get reground to a real nice cam under $100. How much does it cost to put any roller cam in a 340?

I have a real nice 71 340 with a fresh .030 bore job that I am gonna pass on building for my R/T Dak because I want to make 550-600 HP that will last a long time. It is a tough decesion because of the cubes I will give up but 8 cubes is nothing compared to a roller cam and a more solid block

The 360 wins in every case except a numbers matching gold restoration type build.

This topic is a failure unless we start considering the pinionangle.

Until you sonic test a 340 and realize they can be paper thin!

But either one equipped with a long arm trumps them both,....
Keith

This is just like 10+ years ago!! LOL!!

Had a 372" 360 based engine 10 years ago, ran 10.98 NA on pump gas in a 2800# 69 Dart.

IIRC it was based on a very early production 360 block that apparently used the outgoing 340 core, so it was 4.00 bore (stock) but had tons of meat to work with, and was .70 over (or think of a 340 @ .30 over). Crank was internally balanced, knife edged, .600~ lift solid cam, "super stock prepped" rods. Mopar M1 and holley 750 DP.

I was a 340 guy but thought of it as the best of both.

Arguing about which SB is better is like arguing if Syphilis or gonorrhea is better...

What he said

I`ve had numerous 340 combos in my Dart and ran good with them , but my current 360 combo is the fastest of all of them, I am making more power with less compression and cam than I ran in the 340. But then it could be my combination. My new almost complete combo: R3 based 408 with Indy 360-1 heads / pump gas combo I am hoping makes even more power.

Im an odd duck, I like them all, all have their good and bad.

From the 273 up to the 360. I can tell ya my 408 pulls like a train, and revvs pretty darn good for a long arm engine.

I have had both, my 340 ran good but my 360 is faster. It should be though it has better everything in it.

My car was an original 340 car and that is stated on the hood plates. I often get asked what size motor and when I say 360 I get an odd look sometimes followed by "them 340s sure did run" I usually agree or depending on the person I will say yeah, but a 360 is bigger lol.

As far as the cast vs forges crank argument. Its well known that forged is better and I won't and can't argue thats it not. However I have broken a 340 crankshaft and my 360 crank was still alive when the thrust got eaten.

The 360 brings the cheap though no doubt. Mine wiped the thrust out 9 days before drag week this year. I bought a machined crankshaft and bearings kit from O'rielly auto for $188, and had it in less than 24 hours. It made the drive and is still together sofar lol.

Do you want to race your 340 against one of my 360

340's.... you all are talking a 273 with a 4.125 stroke crank, right??? I bet you could take a lot of weight out of that crank during balancing....

I bet a 318 with a 4.125 stroker crank (396) will stomp most Chev 396's.....

I have a 410 5.9 in the works.....

360 wasn’t nothing but a truck motor....

For a street strip cheap build it would be hard to beat a 360 magnum with a reground cam. And a .030 set of pistons with EQ heads. Those heads really move some air with a little work. 400 to 450 hp depending on what you budget for valvetrain upgrades. If i ever do another 5.9/360 it will retain the stock rockers and lift will max at about .520 but still ought to make 425 hp?

Exactly. And anyone with a 340 block or parts wants beaucoup bucks for them just because they are what they are. I have a stroked 360 to 410 cubes that's a beast! Torque monster.

The biggest difference in stock form, 340 ... pre EPA, 360 ... post EPA

[quote=Roughbird72]The biggest difference in stock form, 340 ... pre EPA, 360 ... post EPA

:What does that have to do with an engine you are going to modify. You got me scratching my head on that one.

It means if they're factory stock there's a difference, due EPA restrictions.
IMO, If you build either with premium parts I don't think .040" more bore is going to be a much of difference.

THIS!! I have sonic checked 3 360 magnum blocks and the thinnest thrust was .190, down low close to the mains. along with the roller cam, .020 shorter deck, and the fact that the deck on all 3 was square within .003. The oil passages to mains and pump are also already big, no need to do that step. 4" steel crank and eagle h-beams go in with a small eyebrow notch. Only bad thing I found was main bore diameter being to the high side of spec, but still in spec. Even the chevy machinists commented how well machined, and thick they are compared to a chevy.

back when I was in high school, 1974, my first mopar was a 1970 340 4 speed dart. I had a buddy that had a 71 340 automatic duster and his brother had a 1972 duster with a 360 4 speed, we drag raced on HwyY just outside of town and I could always beat the 340 auto by a car length, the 360 duster just depended on what side of the road I got, we were neck and neck. I currently have a 69 cuda with a 408 stoked 360 with a procharger, 4 speed and man is it fun to drive. Have built several of the 360/408 engines for others and they all really like them. With the reasonable stroker kits today, a 350 or 340 is really a mute point, unless you are restoring for numbers correct vehicles.

All I own are 340s(4 of them now but always looking for more)

I have seen so many dead stock 340 Darts go head to head with 360 Darts and it was always so close, mostly driver. From my observation, the 340 cars would 60 foot the 360 cars but the 360 cars had more MPH in the top end.

But I bet if your buddy with the 340 Auto had yanked that A727 and put in a good shift kit'ed A904 it would have been a whole different outcome.

With no other changes, my 1979 Cop car 360 E58 in a 66 Dart Wagon with the A727 that came with the engine, the A727 was going south so I put my TransGo shift kitted 1978 LeBarron A904 in it with just the trans and driveshft changes and that Dart wagon came alive.

Five year old wisdom , and it is still tough to argue.

And ironically enough, they were made and machined in Mexico (the 360 Magnum blocks)!

Only in Vegas.

forgive this Ford guys , lack of SBM knowledge , but the 2 lines running to the valve covers,........Oil to the rocker shaft ?

Looks like a nascar "truck" motor, probably oil spray rails to cool the valve springs.

I agree!!!
I have owned and raced 42 different small block Chryslers so far. In my opinion the 340 is better if its the 67 to early 72 motors for the forged crank, Higher rpm more reliably Better heads from the factory. Higher compression Pistons, on and on...
,
The cast crank 340's are the same as all the 360 4 barrel motors and hard to tell when racing stock ver stock.
But in racing if you change everything around the 360s are a dime a dozen and if you blow it up the stuff is easy to find. The 340's are desired for doing restorations and racing.
If mopar had been smart and offered in stock form a 360 with a factory forged crank then I would buy them.
You go ahead and bring your 360 powered car around and make my 340 motor match the same and I will show you why the 340 is better. ( same cam, Same heads, Same intake/carb etc and I will out rev you. Out horsepower you, and beat you to the end of the track.
The 340 X, U, O heads all are 2.02 intake valve sized.
The 360 heads only came with 188 valves.
Sure you can upgrade?
and that is another reason why the early 340's rule in drag racing.
The only reason the 360 motors are so popular as most cant find a 340 instead.
Emissions and Cost was why the 360 stayed.
Performance was not much of a though at mopar anymore.
Fuel crunch and fuel embargo's caused it.
in my humble and educated opinion.
Grant Eaton

I much prefer the smaller main bearing bores/smaller crank. The rod ratio was an advantage, even with the resulting shorter stroke. The early, thick wall block is the one to use if you can find one.

Revamped for dry lake bed racing.... yes, spray oiling for the valve springs. Not sure what I’m going to do with it. Supposedly 11 dyno pulls on it.

Bigger main diameter creates more over lap between the rod and main journals making the crank is stronger.That makes the cast crank a pretty decent piece. The stock heads are all pretty much a wash except for intake valve size. The stock 360 lacks compression and cam. However the magnum has the roller advantage and better head. I've run al of them. To be honest I really see no advantage with the 340 except the bore is a little bigger. The magnum blocks have far better machining from the factory. If its getting rebuilt the the pistons and cam are getting swapped anyway so who cares. As far as cast crank strenth? We make well over 800 with a factory 360 crank. I currently have a 340, 360, and a big block. Any body that thinks just because they have a 340 or a 360 and that's the difference if its quick or not makes me wonder.
Doug

Dead bone stock yes a 340 crushes the 360, on paper.

Any one that thinks a 1978 Little Red Express only had a MAX of 225 HP, can I call you stupid and get away with it?

Mid 1980's I had a 1965 Dart GT. I put a 1974 4bb 360 HP in it with the only mods done was a 'True deck' milled the block 0.020", a 340 Resto cam and a Weian aluminum intake. I used 340 Iron exhaust manifolds. A727 with TransGo shift kit. 8 /34 with 3.91:1 SG 225/60 14 tires. I had a Heath Kit CD ignition triggered by my Prestolite Dual Point.

My buddy had a 1964 Valiant 2 door. He had a stock 340 from a Duster. Mallory YL dual point dizzy. He also used the 340 iron manifolds. A727. 8 3/4 with 4.10 SG but he ran a taller 235/65 14 tire.

We weighed within 35 pounds with us in the cars, mine was heavier.

Best 3-4 out of 5 he would beat me by a door.... until I put a set of 2.02" X heads that had been milled a bit. 5 out of 5 I'd win. Yes he 60 footed me every time but I'd run him down between 1000' and 1320' marks.

The only way he could beat me was by removing the passenger and back seats and the front bumper. I raced with my spare tire and jack in the trunk.

Many runs at test and tune nights at Seattle International Raceway.

I still use 340s ONLY... they rev and I use rpm

With good parts anything will rev. Heck they run BAE Hemis well over 9000rpm with 4.375 stroke.
Doug

cant find a 340 to save my life. 360s are all over the place.

Didn't you use a 4" crank in the rampage?

Yes its a 4.00 crank but still a 340 block... this is the first 4.00 crank I've used... I like it

Without added stroke, a 340 is just a bored 318

Don't you wish
AKA aside I have built and raced both stock 340 and stock 360 and then added strokers cranks, bigger is better, thicker cylinder walls on any Mopar LA SB are a lot better
Start your builds with a R block