Engine building questions on a 340

[David Wagle]

I wasn't even sure what to title this subject but here it goes. My engine is a 73 340 with a Holley 650, stock exhaust manifolds, Edelbrock LD340 intake, tranny is a 904 w/3:91 gears. I know the cam is fairly mild and from MP. I put it on the dyno and she came out with 175 hp at the rear wheels. Didn't blow anybody out of the water but it gave me a starting point. I would like at least 300-350 hp at the rear wheels. My questions are. I don't really know where to start. Does anybody have a proven combination that will create this kind of HP, if so what is it? What else will be needed? What kind of tranny work etc?

[goose69]

Well maybe I can help just a little. I had a '73 340 'cuda automatic car and built a motor for it that was sopose to be my daily driver. Started with the stock block and punched it .030 over with trw cast pistons. If I remember right I used '70 340 pistons but I'd have to check. Stock crank, stock exhaust manifolds, but a 2.5in. exhaust with edelbrock mufflers. the heads were stock 360 cast heads with stock size valves, but mild port work and match porting on both the intake and exhaust. I used the 270 comp cam with matching valvetrain, edelbrock performer RPM and an edelbrock 600 carb. Stock electronic ignition. I used a factory high stall mated to a 727 and 3.23 gears. I'm not sure what the perfect match was on this combo, but it would boil the tires and still got good gas milage for what it was. I would average about 14mpg. I threw on a holley 750dp and 3.91 gears one night ant the thing was deadly!! I never did put it on a dyno (although I always wanted to), but it was an eye opening experience for myself and others I ran against. The thing would climb RPM's like an air tool and would walk all over big blocks( hard to say that cause I'm a big block guy). If you're interested I can try and look up in my records and see about some of the specifics of this motor.

[skankweirdall]

Edelbrock or MP aluminum heads. 10.5 to one, with a M1 single plane intake and somewhere near .600 lift. 800 carb and 1 7/8 headers. A 3800 converter and 3.91 to 4.10 gears. If that doesn't make the HP you desire you did something way wrong.

[David Wagle]

If you have the specifics on that engine it would be great goose69. Whatever replies I get on this question I'm going to print out and keep. They say knowledge is power so, whatever I get I'll probabley use some combination thereof when I build my engine.

[fastmopars .inc]

wow skank i think he said 350hp not 550!
haha
but yeah, the combo skankwierdall posted should get you where you want it and probably a little bit more.

[jasontlit]

he said 350 horses at the wheels. Through an automatic tranny...you'll probably need at least 425 or so at the crank...

[6 packin]

freshen up the block, has to be correct, 10.5:1 pistons the a set of Eddy heads, a pretty good camshaft maybe in the 220-230 dur@50 maybe from Hughes or racer brown, a Performer RPM Airgap intake, and Demon, or Holley carb near the 700 CFM range. A set of headers Like TTI's somthing good not headman $99.95 either. Keep the rear gears, get a good converter, and not a 3000 stall used crap (ger) from Ebay, maybe Coan,Dynamic, or ATI. MSD 6AL ignition. Get the rotating assembly light as possiable, Like Ross, KB, or diamond pistons, and maybe a set of Eagle SIR rods, there lighter and stronger than stockers. Get a good setup on valve gear, like comps Steel roller tips, or crane ductile adjustable ones. This would be the package you can be happy with, on the street or at the track.

[dave571]

"At least 300-350 at the wheels" is a tall order.

400 or better at the crank. Skankweirdal is on the right path.

David Waigle, what is your budget?

[440barracuda]

I just got a 340 block and heads, not sure if it has X heads, how can i tell? i want a 11 second Dart, what should i do? I would like to run a auto, and have a dana 60 on hand. I want it to be a strett/strip car. can anyone here help?

[David Wagle]

I appreciate all the input. Dave571, haven't exactly figured that out yet. Figured I would get ideas then start pricing the materials and labor. I know to create that kind of power won't be cheap.

[skankweirdall]

The problem here is it would be easier to get there with more cubes. I used a 340 for my Duster, it ran 11.70's just like I drove it on the street except to lower the rear tire pressure. Anyway you may not like the combo because the bigger heads and the small cubic inches like to be twisted. 340 +.030, .590 MP cam, W2 heads, midly ported. Crane 1.6 roller rockers, TRW replacement 71 pistons, M1 single plane intake and 800 carb. T/A 4200 stall speed 9" converter. 4.56:1 gears, 29 inch tall tires 12 inches of tread, Heddman 1 7/8 headers, Flowmaster 3 1/2 to 3 reducers to a 3 inch exhaust to 3" in and out Flowmaster 2 chamber mufflers with turn downs at the rear axle. Battery in the trunck, rearched 3000# S/S springs and drag stars all around. Trans was a 904 with a T/A reverse valve body. Aluminum radiator and electric fan, no mechanical fan. You'll be twisting this combo around 7500 to 7800. Choose valve springs (you'll need the 2 inch installed height) that have about 140 to 155 on the seat and about 440 over the nose. Break your cam in with just the outer springs and then install the inners.


Or you could use my combo above which relies on a smaller port cross sectional area to keep the velocity up. This way you won't have to twist it as hard, you should still do some bowl and guide work on those heads though. Use 1.5 rockers and you'll be set. You'll still need the 3" exhaust as well.

Happy Moparing

[David Wagle]

Which would be better to go with, the factory heads with I assume some work or aluminum heads from Edelbrock or I think someone mentioned MP? How much are the Edelbrocks? Can someone give me an idea on cost to get the same performance from factory heads?

[skankweirdall]

Get a Summit and/or Jegs catalog or something like that for some price comparisons. Also check around the web at Muscle Motors, Indy Cylinder Head, etc.

As for the factory heads, forget it. The exhaust side is poor in comparison to anything else. By the time you got a set of factory heads to flow what midly worked Edelbrock or MP heads would flow you will have already spent more than getting the aluminum heads in the first place. On top of that you will be pretty maxed out in the head department where if you got the aluminum heads you'd still have room for improvement.

[David Wagle]

Just got a new Summitt catalog I'll check it? Anyone ever buy anything from Mancini Racing? I know they have engine rebuild packages etc. I also considered a crate engine but I really like having the 340. When I first joined the military I had a 74 Duster with a 318. I was young and used to read all the Mopar Mags about the "potent small block that was the 340". At the time I could never quite swing the $ for a 340. Now umpteen years later I finally have one and honestly couldn't be happier or more excited about it. Kinda like a kid with a new toy at christmas!!

[skankweirdall]

I loved my 340 even though I've got a whole lot less money in the 360 short block, it's not the same. The ET didn't really change but I had to go from a 5.13 gear to a 4.88 and although the 360 leaves a little harder it doesn't run on the top end like the 340 did. That 340 was king of the top end charge. The 360 is kinda whimpy upstairs.

[rumblefish360]

In simple terms, an Edel. RPM package with some porting and a better cam will do it. I would have a comp. ratio of 10.5-1 in doing that.

6 packin is on it I think & skankweirdall's is a little overkill, but sounds real yummmmmy.

skankweirdall; That's what a little stroke will do for ya. That's why I chose the 360 for the street. Just a few more foot pounds, a few less revs.

[David Wagle]

I checked the Summitt catalog. It shows the Edelbrock heads for 361-440 Chryslers. Will those fit? Rumblefish, is an Edelbrock RPM package just the heads?

[George G. Leverette]

David maybe this will help, I have a 72 340 Duster with 30 over Mopar 340 high swirl port heads with all stainless valves cost about $875.00 to purchase all parts then I installed them. MSD 6AL from Mopar, early 340 exhaust manifolds, 2 1\2" pipes with cross over, 355 rearwith suregrip. I ran 51.1s on a couple of passes at LACR taking it easy because the engine had only 500 miles on it. forgot the T.Q. carb. The car is a daily driver with A\C and power steering. The 74 Duster has the 360 short block from Mopar with eddy heads from Indy bought them for $1.249 because they install sorings for the cam youy running. This combo is not as smooth as the 340 because of the Hughes cam. The Mopar 508 is on the ragged edge for a street cam but once past 2600 RPM its monster time.

I gave both examples because if you drive the car often the spinning wheels and loud exhaust gets old real quick. There are some real nice stroker kits that will give you the best of both worlds???????

[skankweirdall]

No David, those are big block heads. You need the ones for the 318-360, The LA small block. Call them up, they have a whole bunch more stuff than what is in the catalog.

When I was building my car if I needed a MP part that was on back order from Mopar I'd call Summit and sure enough, they had it in stock. Even though it wasn't listed in their catalog.

[David Wagle]

Great! Thanks for all the info. Skankweirdall, I thought those were for big blocks but didn't see the small block heads listed. I'll give them a call and find out for sure on a price. Like I said I'm going to print all this stuff out, it gives me some good ideas on what I need. Last thing. There's no need to switch the 904 for a 727? I always thought the 904 was more of just a passenger car tranny?

[skankweirdall]

Summit has them listed with the Mopar Performance stuff.

I use a 904 in my Duster.

[skankweirdall]

Originally posted by rumblefish360

skankweirdall; That's what a little stroke will do for ya. That's why I chose the 360 for the street. Just a few more foot pounds, a few less revs.

Yeah, but since I'm one of the faster cars in the class I'm usually chasing my opponent. That top end charge really fools them, so I miss it. I've got a siamese bore R3 block and a new 3.31 stroke crank so I'm thinking real hard about building a 4.185 bore/3.31 stroke 365. I'm thinking that will give me back my edge and maybe a few more ponies to boot.

[rumblefish360]

skankweirdall;

No David, those are big block heads. You need the ones for the 318-360, The LA small block. Call them up, they have a whole bunch more stuff than what is in the catalog.

Good lookin out.

I like that big bore thinking. Big thumbs up there. I'll be doing a 400 that sits in wait in the corner here. Rev baby rev.

[rumblefish360]

David Wagle;

The RPM package is carb, intake and heads. They suggest 1 3/4 tube exhaust pipe. They also have a bunch of other things on the engine. Cams, but they could be better, go MoPar at least. Air cleaner, valve covers and such.
I suggest the basic go fast parts. Head and intake, carb if ya like them. I prefur the OE Carters over the Edel. Carter copies. Followed by Holley then Demon carbs. They also have mufflers that flow well.

[David Wagle]

Got it, thanks Rumblefish.