B Bodies & 340’s

[Moparfiend]

I would like to know some specifics regarding the automatic drivetrain combinations used in say Roadrunners with 340’s.

What rear end and torque converters (stall specs) were used along with engine compression ratios and camshafts specs if possible.

Thanks MF

 

[R413]

First year for a road runner with a 340 was 1971. Because the
340 is down on torque with 340 ft lbs compared to a 383 with 425 ft lbs of torque.
And 340 is down on horsepower with 275 compared to a road runner 383 at 335 horsepower. A 1966-1970 b-body is a heavy car, that's why the factory didn't put a 340 in them.
340 was an A body only engine in 1968-69, and really make a good combination.

1971 road runners were smaller and lighter cars by about 300 lbs depending where you get the numbers. Better aerodynamics also.

 

[Moparfiend]

See my update below

 

[Moparfiend]

If I’m not mistaken, the 1970 was rated approximately 200lbs lighter than the 1971. But 3/10 sec. in a quarter mile isn’t a big deal either, but let’s not go there because this is not what I was asking for.
I am however, asking about the set ups. Anybody out there with a 71 to 73 roadrunner with a 340 in it that wants to comment about their configuration?

 

[Bighouse]

I’ve got a 69 Charger with a 340/727. The casting date is late 69 on the block. I bought it like this. The only thing I know about it is it has a crane rocker set-up and some lumpy cam, an edelbrock manifold and carb, HEI distributor and headers. It’s faster than I thought it was going to be.

It had 3:55’s that I swapped for 3.23’s for a little more highway.

Don’t know if that helps, but I like it.

 

[Nacho-RT74]

Searching on the hamtramck registry website (dealership data books) you’ll find several specs about axle ratios, compression and basic stuff like that… but no mention to more technical stuff such as TC stall or specific camshaft specs… just says “hi-lift”.

And the “compression ratios” is just a number based on engines IF were cut “blue printed”… which was not! LOL

 

[DeltaV]

TC tables and the procedure for stall testing are in the factory service manuals. Similarly, compression ratios, valve sizes, valve timing, and etc. are identified.

Factory Service Manuals and other data are available for download to your computer for FREE.

The mymopar website is nice:

Service Manuals – MyMopar

Happy reading!

 

[DeltaV]

This is an interesting article; and see the part about "Bogus Numbers":

340 Production Numbers and Specs

 

[HawkRod]

My 73 Road Runner was equipped with a 340, 727 and 8 3/4 rear. I believe that all 340s got 727 transmissions, and likely 8 3/4 rears too. But I am not 100% certain about that and I'm sure someone will correct me if I am wrong.

My particular car had a 3.55 sure grip, but 3.23 open rear was standard. I don't know the stall spec of the torque converter though.

 

[Moparfiend]

I’ve got a 69 Charger with a 340/727. The casting date is late 69 on the block. I bought it like this. The only thing I know about it is it has a crane rocker set-up and some lumpy cam, an edelbrock manifold and carb, HEI distributor and headers. It’s faster than I thought it was going to be.

It had 3:55’s that I swapped for 3.23’s for a little more highway.

Don’t know if that helps, but I like it.

Thanks I didn’t know they put those in chargers back then

 

[Moparfiend]

My 73 Road Runner was equipped with a 340, 727 and 8 3/4 rear. I believe that all 340s got 727 transmissions, and likely 8 3/4 rears too. But I am not 100% certain about that and I'm sure someone will correct me if I am wrong.

My particular car had a 3.55 sure grip, but 3.23 open rear was standard. I don't know the stall spec of the torque converter though.

What was the performance like just out of curiosity?

 

[RJS]

Thanks I didn’t know they put those in chargers back then

They didn't but someone must have. And back to 1971 B-Body's as stated 3.23's 3.55's and 3.91's were available.

 

[YY1]

I disagree about 66/67 being heavy cars.
A 2 door "23" body 66/67 is light as hell.
Almost as light as an A body.
...but the 340 was introduced in 68.

71-73 RR and Charger 340 cars could have 3 or 4 speed manual trans not all 727.
71 through 73 came with 8 3/4 axle.
Sometime in the 7-74 production changeover, the 9 1/4 axle was introduced.

 

[Bighouse]

Thanks I didn’t know they put those in chargers back then

As said earlier- they didn’t. My car was originally a 318

 

[HawkRod]

What was the performance like just out of curiosity?

In 1973 the 340 had reduced compression (don't remember the ratio but you can look it up), and a shot peened cast crank with external balancing. The heads also had smaller valves. IIRC, the horsepower was rated at 240.

I was 16 when I started driving it, and over time I added headers and a better exhaust. It actually ran OK, but a few years after I got it the oil pressure was low enough that I rebuilt it to 69 specs with a hotter cam. I upgraded the heads to 2.02 intakes, like the 69 spec. After that, it really ran strong but needed really good octane to run well. After a time I tired of having to put octane boosters in it, so I reduced the compression to 9.33:1, using a special cut that improved quench area that my father-in-law sort of developed at the time (now it is common). I swear after reducing the compression the damn thing ran stronger than it did before.

Bottom line is I have a GREAT respect for 340s. They are an engine that Chrysler just got right. Build them right and they will run like a scared ape!

 

[DeltaV]

340 compression ratios as per model year FSM:

10.5:1 for 1968
10.5:1 for 1969
10.5:1 for 1970
10.5:1 for 1971
10.2:1 for 1971 cited by internet sources.
8.5:1 for 1972
8.5:1 for 1973