Tips on building my 1973 Dart Sport 340

[moparmadman440]

Hey,


I was wondering if any of you Mopar guys could give me some knowledge on building my 1973 340 for my Dart Sport. I just bought the block and it is currently being machined. The block has checked out good as for no cracks and the line bore is fine. The machinist said that .30 over would do the trick on it. This is the first engine I am going to try and tackle rebuilding. I am just 19 but I have a passion for mopars and worked a lot on them but never done a rebuild. The heads that came on that year block reduced the compression but I don't have those heads anyway............ so I need heads for one thing. Any info that you guys could give me would be greatly appreciated.


P.S. The pistons that I have bought for it are Keith Black pistons .30 over, forged, with big valve reliefs. The compression will be about 9.0 - 9.5

I want this car to be a daily driver but also a force that imports can't reckon with!!!

Thanks for the advice



moparmadman440

[1972roadrunner]

i've got J heads on mine... i'm not sure of the year of the block... go to http://tmezz.mezzweb.com:81 to learn more about it. course, right now the motor is half torn apart in the garage on a motor stand while the car is in the driveway with no hood/motor... i think i spun a crank bearing, not sure till complete teardown probably tomorrow (its 12:41am now).

if i was you, i would use studs on the main caps, good bearings, steel crank, steel or equally strong connecting rods, forged pistons (mine are rated at 12.5:1 but the open chamber design of the J heads makes it much lower...probably AROUND 10:1 but i'm not too sure..). what kind of intake/carb are you plannin on using? i'm using an edelbrock torkerII aluminum high-rise intake, and a Holley 650 double pumper. runs GREAT! well, till smoke filled the block and the starter couldn't hardley turn the motor...

good luck! and congrats on purchasing a great block! i must warn you though, your wallet will be beaten and might have many holes in it by the time your done rebuilding! i put over $4,000 into mine and DIDN'T get a crank, rods, heads, intake, carb....basically the most expensive parts... now we're thinking about putting more money into the bottom end now that we have NOS..... course, i haven't run it yet...can't wait! gotta get the bugs worked out first...

[Dartcustom]

You could go the stroker route, since it's already torn down. Would make a mean smallblock.

[rumblefish360]

A storker is a good idea. Return the KB pistons if you want to go that route.
A good compresion for the street is a max of 9.5-1 for iron heads, 10.5-1 with aluminum heads. Pocket port your heads w/2.02 intake valves, grab a Comp Cams 280* cam and liffters w/springs.
A 650 (Min.) carb and a Edel. RPM intake, MSD ignition and headers.
This should grab you about 400 HP.
An every day cruise machine can use 3.55's with a wider, slightly taller tire.
MoPar has good iron heads. They can be purchased allready ported and complete, ready to bolt on. (As I was thinking about above.)
Edelbrock has Aluminum heads that are bolt on.
The next step would be the MoPar W-2 series head for some BIG Whoop A$$ performance.
All heads should be checked prior to being installed on the engine.

[moparmadman440]

Rumblefish,


Should I stick with the cast crank and the stock rods, if I have them checked. And if I chose to stroke it how hard would it be to do. I want to know what options I have available to me. Me friend has a car just like mine with the 340 and its really fast.......mustangs are nothing to him. Of course he is running a 100 shot of NOS but he never hardly has his bottle filled and in the car.

Thanks for all the ideas guys........... I don't know where I would be without Moparchat, I have learned so much just from reading things on here!

[1972roadrunner]

moparmadman440: i have my stock rods and cast crank, but i'm not sure if we're going to keep them... motor is out of the car and on the stand... if your budget can support it, I would go with steel crank and rods...thats just me though .

also, i love your sig!! theres a guy at work that says mopars suck . he's into that import shit too! if i see him tomorrow i'll have to drop that line by him .

[dave571]

Mopars suck?


That's what a lot guys say at the lights. Usually it's right before the light turns green, and I hand them their ass.


Back to the topic
Every one has different ideas about what money well spent is. A good example is the cast vs steel crank.

The steel crank won't add a single horse power to your engine.

On the other hand it does make the engine less likely to come a part.

On the other hand, not many brand x engines run forged, so why do we need steel?

See what I mean???

The bottom line is, that if you want to make power on a budget, the power comes from the heads and the cam, (and having enough compression to run the cam)

From there, your accesory combination makes the difference. If the engine is torn down, your cheapest horse power is in mild port work, and port matching the heads and manifolds. It makes a big difference, and doesn't hurt you on the bottom end like some things do.

[pro-street dart]

I'm building a 73 Dart Sport too

It's a original 4-speed car that's now tubbed with a ladderbar suspension, dana rear, and a stroker 340 with a 2x4 carb set-up.
Good luck with yours and good choice!!

[rumblefish360]

Should I stick with the cast crank and the stock rods, if I have them checked.

They should be fine for a good amount of HP.
Stoking the engine is as easy as ;
Getting the crank and pistons to match the new stroke. The machine shop might have to do a little work on the block so the new crank can swings the rods around without hitting the block. It's just a little notch the machinest makes. This will take some time to do. It's not just a swipe with a dremel.
Then the rest is like ant other engine.
People stoke there engines to gain Torque from the add stroke and the new CID of the engine.
The car now becomes much easier to move with the same peadal travel.
There are kits out there that make this easier and quicker.

[Doug Wilson]

The cast crank and 340 rods should be good to 7000. You should have the engine balanced if you plan to twist it that tight.