The 340

V8 Sam · Post by **V8 Sam** » Fri Mar 22, 13 6:38 pm

Right, I often hear about how good this engine is..

but I never fully understood what made it stand out amongst the rest?

read many an article saying the 340 engined Abods where a match for the much bigger 440 lumps etc. (all though i probably assume this is down to weight of the full size motors)

is the 340 more desrible over the 360? if so why?

Pete · Post by **Pete** » Fri Mar 22, 13 6:46 pm

I think a bit of it is folklore - a bit like the Chevy 327; but the 340 is a GOOD engine. A lot of it comes from the Trans Am motors which had very good heads and provision for 4 bolt mains, but not fitted in the factory.

I have been fortunate to have had 3. A 340 with a 4bbl vac sec and 2 with six pack set ups.

They are immense fun, are light, have good port flow and rev freely.

A 340 is a velociraptor compared to a 440 T-Rex; very different animals; but both could rip your head off.

340 is a very nice street engine in either "A" or "E" body....

Pete · Post by **Pete** » Fri Mar 22, 13 6:50 pm

...and Gavin and Dave Bishop will be along soon to tell you how similar a 340 and a 360 really is in a minute....I think the lower compression and the "Smog motor" tag has given the 360 a bad press.......

Dave81 · Post by **Dave81** » Fri Mar 22, 13 7:59 pm

340 was part of the original Scat pack and Rapid Transit System. It was the engine to have if you wanted a small block back in the 60's & 70's.

Have to say they are great and when they scream they sound bloody fantastic. But, with the cost differential and aftermarket parts i'd take the 360 every time. If you have a 340 then great. Not sure i would pay the premium for the long block over a 360. £ for £ today the 360 will be the more poweful engine in any price determined build!

Both great engines whichever you choose, and i will admit there is a cool factor to saying you own a 340!

Just my opinion...........

MrNorm · Post by **MrNorm** » Fri Mar 22, 13 11:03 pm

Agree with Pete (as predicted!) and Dave, 360 is better bang for the buck, and 20 more cubes to boot. Cheaper, more plentiful, no real differences (Talking early LA engines 340-360). No brainer......

Having said that, one of the few decision where I let my heart rule my head on my car (obviously painting it pink was another one

) and went with a 340 as Dave said just for the cool factor (to me that is). And it's not even 340 cubes as it is stroked - but it is a 340 stroker and not a 360 stroker!

MilesnMiles · Post by **MilesnMiles** » Sat Mar 23, 13 6:26 am

Dave, it's not quite as simple as 360 better than 340 for equal $ on parts.
The rod/bore ratio on the 340 makes for a easy high revving engine, the 360 tends to be seen a s a good basis for a torque monster.
When my 340 finally hits the road I'll report back with a 'seat of the pants' indication. I ran a 360 for seven years in my old Dart. Nice engines.

Carl · Post by **Carl** » Sat Mar 23, 13 10:33 am

It's all to do with stroke ratio. The 360 has a longer stroke which will make more torque than the 340, but the 340 which has a bigger bore will make more HP per cubic inch. In short the 360 will be a better street/strip engine but the 340 will be a better racing engine, look at the success it had in Nascar. Both engines (pre74 360s) can be bored out to 0.040 later ones had thinner cylinder walls to make the engine lighter so 0.030 would be the max. Both engines have their cams high up in the bloke which is great for stroking as it allows for a longer stroke. The 360 has bigger mains than the 340. Having said all that this is just what I understand. But there must be a reason why the 340 was used for racing rather than the 360? And I believe the only real racing 340 block where the 'X' blocks or the later 'R' 'R1' 'R2' etc blocks but you will prober my never find 1. These had provisions for 4 bolt mains. As I say this is just my belief

Jim · Post by **Jim** » Sat Mar 23, 13 10:33 am

The 68-71 340 is a wonderful engine, with high compression and big valve heads it's a little screamer. They tamed it for 1972 with lower compression and smaller valves.

There's nothing wrong with a 360. Some people don't like the cast crank, but that's OK with me. I had a built 360 in a Duster many years ago, and that car flew.

But yes I do have a soft spot for the 340, it's one of my favourite engines, and it works very well in an A or E body especially.

Blue · Post by **Blue** » Sat Mar 23, 13 11:17 am

These days the 360 is the better option, plenty of cheap ones about and aftermarket parts to build whatever you want. 340's are too hard to find and too expensive, so not much point unless you really must have one.

MrNorm · Post by **MrNorm** » Sat Mar 23, 13 11:35 am

Yes the 340 does rev a little better. But remember we are not talking night and day, the 340 stroke is about 7mm (in new money) less, and the bore is only 40thou more. In fact if you get an early 360 block (which used the same cores as the 340) and bored it 40 thou, you would in effect have a virgin (standard bore) 340 block apart from the larger journals.

So I agree, if you want a standard displacement engine for racing (rpm) a 340 is th better option. Any other application 360 makes sense. And tbh, if you are building a decent engine, I can think of no reason not to build a stroker these days, in which case the stroke becomes the same for either.

BTW - X blocks, R blocks were all aftermarket (Mopar) blocks. Never used in a passenger car. No LA engines ever had four bolt mains, though the TA blocks had provision for them.
Also the 340s had cast cranks too from (72?)

Les Szabo · Post by **Les Szabo** » Sat Mar 23, 13 12:22 pm

To put it plainly Sam without getting too technical, the block/pistons creates a certain demand of air for the cylinder heads to supply it depending on size of the bores and the stroke which is the speed it wants it.

The 340 2.02 cylinder had large enough valves and intake tract to supply that demand very well and then some in stock form, which is why they respond so well to a big cam and carb and will make good hp and torque., much like the SB Chevy's.

How much you squeeze the fuel/air mixture once its sucked inside the chamber will depend on how big a bang you create (10.5:1CR) on the downward stroke which is power.

Thats why a 360 is more referred to as a torque engine, cos of there lower 8.5:1 CR. and longer stroke. Less demand, slower and less bang at the top.=less hp.

You can make a 318 into a lively motor by simply installing 10.5:1 slugs, a pair of 1.88 valve 360 heads will do and a decent cam, then your back to heads that can supply air to the bores demands and off you go on the tuning route. Basically you are re-creating a 340 but with a smaller 318 bore.

In comparison, a 440 has a BIG bore, its demand for air exceeds what a stock 906 head with its 2.08 int valve and a similar intake tract size to a 340 can reasonably supply it, thats why with the extra weight, and sluggish performance, a Small Block with a relatively mild tune could out perform a BB car sometimes.

Anyhow if you haven't fallen asleep yet reading this

...thats what its mostly all about.

Les

Carl · Post by **Carl** » Sat Mar 23, 13 12:31 pm

And don't forget if you are changing to a 340 or 360 from a 318 you have to change the left hand engine mount as I believe they are different brackets on the 340/360 block than on the 318

pete walton · Post by **pete walton** » Sat Mar 23, 13 12:57 pm

http://www.racingjunk.com/Nostalgia/291 ... -Drag.html
Nice little project ,and at that price a bargaaain..Not sure about the way the scoop is nailed on ,but still nice in my book,,,Duncans six pak inlet ,bit of fettling and you have a sweet little race car

V8 Sam · Post by **V8 Sam** » Sat Mar 23, 13 1:15 pm

Not planning on doing a anything to my motor yet.

I believe it is already in a mild tune state as it is. And it runs very well. Maybe next year I'll play a little. Especially if it's just a case of finding the 340 heads etc and if it's all matches up 'plug and play' stylee

But right now its all about sorting the main car first....when ever the weather lets off.

Mick · Post by **Mick** » Sat Mar 23, 13 1:25 pm

If 15 yrs ago, i knew what i know now, that and the parts availibilty, stroker kits etc. I would have gone the small block stroker route, with either ported eddy's,indy's or W2. Push for 550- 600 hp and have 150 lb less on the front..
Mick