340 Build Spec's

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69Dart

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Just scored a 340 that has never been apart and also bolted to it was a 727. This combination will be going in a 68 Dart that will be for the street. When I say street...its going to be a daily driver and need to run on low to middle of the road fuel.
Still want it to run faily well but not crazy built. Would like to hear a little cam lope..
OK..here is your chance..what would you put into it..

Thanks
Rick
 
9.0 to 1, Factory heads, bowl ported and matched, Air Gap, 3310, headers 1 3/4, Comp 268, file to fit rings, stock lower end. You can substitute TQ and factory TQ manifold if you want stock look, and they will work good. I believe 1 5/8 headers are too small for 340/360. this would be solid street performer, run on middle grade fuel and be turn key. If you need more, you can add more camshaft and head work. Good luck. Terry.
 
I do the close to the same, minus the bowl work and gasket matching, run the 1 5/8 headers, add a little compression, and run the old Comp 268H High Energy cam. With a '71 T quad intake and carb, mine went 13.0 in a 74 4sp Cuda with 3.23s, drove it daily for 2 years, and passed emmissions twice. That was back when I could shift tho...lol.
 
The 71 TQ was a solid fuel carb. 72-73 was a better unit. 71 manifold is good. Scamp be careful on the compression if you want to run low or middle fuel. Short cam won't allow much. 1 5/8 tubes loose 7 % on 340/360's. I learned this from a Hedman engineer many years ago. TTI steps will work, but expensive. Bowl porting is easy and cheap if you do this yourself and there is no penalty. Clean up the bowls and blend into the bottom cut. Low lift flow is better and more flow everywhere in the flow curve. Also back cutting the valves is inexpensive and pays off big in low lift flow. Good lick. Terry.
 
headsbikesmopars said:
9.0 to 1, Factory heads, bowl ported and matched, Air Gap, 3310, headers 1 3/4, Comp 268, file to fit rings, stock lower end. You can substitute TQ and factory TQ manifold if you want stock look, and they will work good. I believe 1 5/8 headers are too small for 340/360. this would be solid street performer, run on middle grade fuel and be turn key. If you need more, you can add more camshaft and head work. Good luck. Terry.
Click to expand...

FWIW, I have been following a lot of these tech articles in the Engine Masters series by Popular Hot Rodding and in the past month they did an article on headers. This was a big block engine but they tested in succession 8 different sets of headers from 1.75" tube to 2.25" with different length tubes and collector configurations.

The conclusion: All the different headers made with in 1 HP and 1 FT-LB average over the 2500-6500 rpm test range. They could suffle around the torque peak and change the shape of the torque curve but the averages stayed the same.

General design guide lines tell you the larger the tube diameter of a header the higher in the rpm range the torque peak occurs. So if you are building a daily driver motor stay with the 1 5/8" headers you will keep the power down in an rpm range you can use it.

A 3310 is also to much carb for a daily driven car, you would be much happier with something in the 650cfm range. Again another article where a 383 stroker small block in a Camaro was bing tuned on a chassis dyno. They were limited in what they could do to this engine because the goal was to keep it 100% California Smog legal. I believe they were testing up to about 6000 rpm maybe 6500. The engine had a 600cfm 4160 Holley vacuum secondary carb. At the peak test rpm they only had 0.8"Hg manifold vacuum which indicated that the carb was not resricting air flow into the engine.

The bigger carb may give you a slight edge in the upper rpm ranges (above 6000 rpm) but it will be at the expense of throttle response in the lower rpm ranges you will be driving the car. You will also likely see a mileage advantage with the smaller carb too.
 
moper said:
I do the close to the same, minus the bowl work and gasket matching, run the 1 5/8 headers, add a little compression, and run the old Comp 268H High Energy cam. With a '71 T quad intake and carb, mine went 13.0 in a 74 4sp Cuda with 3.23s, drove it daily for 2 years, and passed emmissions twice. That was back when I could shift tho...lol.
Click to expand...

I agree with Dave. This should be a great driver.
 
That was kind of where I was going. 1 5/8 keeps the 340s "limited" torque down where a street geared car likes it. Not max hp, but usable power low down. You can do the bowl blend, it will only help, but you dont have to..Mine was doen before I did any port work, so they were a 3 angle stone valve job, and no special anything. I would bump static up to 9.5-9.8:1, again, to keep the torque peak lower. I dont think this would be any problem with a properly curved distributor. I would avoid the Holley carbs all together, because i like Carters or Edelbrocks for idles quality and throttle response on stock or almost stock builds. (back to that emmissions testing..lol..Holleys are rough to get through..) Just different tastes for different guys.
 
Carbs are a very much a personal preference thing. I have heard just as many people complain about all the brands for all the same reasons. What ever carb you select you better plan on doing some tuning (more than just turning the idle mixture screws) to get the most out out of it or you won't likely be happy.

I believe the reason for the 4160 Holley was it had a CARB exemption for that car which made it legal.

FWIW, I still have the 600 CFM 4160 on my 360. I had to go down from the stock #69 primary jets to 65's to get the mixture close. Still using the red pump cam but have it in the #2 postion for a little more initial squirt. The carb seems happiest with the silver spring in the secondaries (the next softer causes a slight bog when the secondaries open and the next stiffer doesn't seem to run as hard). The idle screws do not have much effect so I think I need to open the secondary stop a wisker so I can close down the primaries some. I have about 14" Hg idle vacuum so I want to go up to an 8 or 9 power valve to see if I can get rid of that last bit of tip in hesitation. The interesting thing was the article with the 383 and 4160 as they tuned that carb they wound up with pretty much the same settings as I have by using my butt dyno and reading the plugs. They did do some custom work to the secondary metering plate to richen the secondaries.
 
Sorry Rick, I missunderstood. Didn't know you were going for a stump puller. I was giving you a combo for a street driver and good performer that was fairly cheap to put together and would be low maintenance and turn key. All on pump gas with a lope. Ma Mopar did pretty good with that 800 TQ on a stock engine, with 8.5 compresion. You have much to consider. Good luck on your project, Terry.
 
As of 11/23/05 we lost the 340 that we were suppose to get! Now we have a couple of choices left that I am not sure which would be the best.
We have a 73 Challenger sitting in the back yard that was either going to a new home as a complete car or we could pull the 318 and tranny out of it for the Dart. I know its not the 340 that I really wanted for the car but the only cost in the motor and tranny would be the rebuild. We could look around and put a 360 in it but what do you really gain execpt cubic inches. If this car was going to see a lot of time at the strip then that might be something to consider. But this car is going to be a daily driver and may see the strip a couple of times...
What do you think????

Thanks
Rick
 
For the last couple of days I have been looking around Ebay @ 68 Darts. The cars that I have found are sporting the 340 motors. In the build on my son's 68 Dart I do have access to that 318 out of the Challenger but its not what "Dad" wants for a power plant. I know it sounds stupid that I would want something different when the 318 wont cost any money execpt for the rebuild. But that is not what I want to put in his car...I want a 340...
I guess you could say it was a dad thing.. Now what I need to do is locate a 340...HELP!!!!!!

Thanks
Rick
 
Since you are deviating from stock anyway 360's are much more plentiful and a bunch cheaper than a 340. Comparatively built, the 360 will make more power at a lower more street friendly rpm than a 340. You can always dress it out with a 340 pie plate on the air cleaner, the only way anyone would know is they crawled under the car and looked at the casting numbers on the side of the block. Think of it as a stroked 340 (which is what it is).

Or, you can take that 318 you already have and rebuild it with the MP 4" stroker crank and have a 390. For sure you will need to replace the 318 heads with 340/360 heads.
 
Good luck finding a 340 for a reasonable price. They are hard to come by. Do like Dave suggests and get a 360 core... or stroke the 318. A 360 crank with cut down mains in a 318 bored .030 over would give you 349 cubes.
 
I'd bet doing the same mods (change the ehads to a set of Magnums) to the 318 and you and your Dad wont be able to tell the difference, and you'll be beating up on 340s and 360s at the track. I have 2 340 cores, and a 318. I'm building the 318 next for my truck, to replace the 360. The 349 idea is a very good one, and fairly cost effective, except for the balancing work.
 
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