The 340 Mopar Engine is still one of the most popular Mopar Engines from the ’60s and ’70s. Some Mopar Engines were designed for drag racing. They were heavy and bulky, but put-out high horsepower. This made them great for straight line races, but anything that involved curves they struggled. That’s were the quick-and-nimble 340 Mopar Engine found its calling.
The 340 Mopar Engine was developed in the 1960s and found its way to production by the end of 1967. It was close in cubic inches to the 318 Engine, but they differed in a whole lot more than just 22 cubic inches.
The 340 had: high performance heads, special carburetor and cam; New oil pump with a 90 degree adapter; 2.02 inch intake valves and 1.60 inch exhaust valves; Dual Time Chain with windage tray; high-rise dual plane intake.
Even with all of these performance features the top “horsepower rating” that any 340 Mopar Engine was 290 horsepower. This was the 340 Six Pack version debuted in the Dodge Challenger T/A and AAR ‘Cuda. Many believe that many Mopar Engines’ horsepower were underestimated to cut down the costs that buyers would have to pay for their insurance. So the actual horsepower of these 340 engines are most likely more than the rated 290 horsepower.
Stock 340 Mopar Engine Characteristics
Figure 1 show the performance characteristics (power curve) of the stock 340 engine. The maximums were at 281 hp at 5200 rpm and 328 lbs/ft at 3900 rpm. These numbers are right on target for the the factory ratings on the 340 high performance which were 275hp at 5000 rpm, and 340 lbs/ft at 3200 rpm.
Share Your 340 High Performance Modifications
How have you built up your High Performance 340 Engine? Share in the comments!
I owned, built, and raced my 68 Barracuda 340-formula-S automatic convertible in 70-71. I stated in J-stock auto, S/S-H, and finally E-Modified. I put Larry Atherton’s cross over oil system mods in, ran alum rods & pistons, solid lifters, HD valve train, 80psi oil system, etc etc. dual 780’s on a tunnel ram, 5k stall conv, and modified my 727 torqueflite with hemi bands and pro-stock shifter. With 5:33 gears and shifting at 9k(!) I was in the 114-116 mph range. Best times: 11.88-11.98-12.02. At 19 I was guessing on everything, but have the best memories of my time. Painted Original Flying Machine in black & gold Gothic letters on my front fenders. One helluva ride.
HELLO
I have a 70 dart swinger with 340 J heads hi rise intake ect want to know about it?
I just received three dusters 2-70s 1-74 came with six motors six transmissions four rear ends three sets J heads mini oven parts oh our late 60s 340sWill be selling some parts when I find out what I have
I have 340-6 AAR. The car definitely feels like it is faster than 290hp but I really think the numbers are close but the lighter motor and 391 gear does make the car very punchy and faster feeling than the big block E bodys.
Oh yeah and Terry moss you’re either smoking crack or just a full of shit lie. Nothing you’ve written is even close to right.
I have 2 340 engine blocks and a forged steel crank that has been totally checked out by Pittsburgh Crankshaft. Tag is with it. Still in the box from there. Selling all 3, plus I have a fender and trunk lid for a 71 duster. email at chucklesmax69@gmail.com
i have a 1970 340 x heads that was built for a stock car its home now is a 1986 D150 i would like to bring power range down a bit like 1000-to 6000 rpm 10.5.1 .30over any recomend for a cam would be helpful