help with 73 340

[340plot]

hey guys, i am picking up a 73 340 duster that is the original engine in it. i am wondering all the differences in the enge compared to the older year 340's i know it has lower compression and smaller valves.
are the exaust manifolds the better flowing ones? same as the older 340's? i beleive that the heads have smaller valves, but what can i do to them to flow like the x heads? do the 73 heads hive big ports like the x or j heads?
what would i need to buy to have the h.p of like a 71 engine? pistons? which ones? heads? which ones? exaust manifolds? or the 73 ones ok? should i go with a bigger cam?
how about i aske a little differently. what are good choices to get this engine to be able to be driven every day, and still push 400 horepower? without nitrous or stroking it?
thanks for all the help guys
here are a few other questions..... a 73 340 duster came factory with a 904 or 727? 8 3/4? cause the rear in the car now is not a 8 3/4

 

[70aarcuda]

73 340 heads are J heads....just replace 1.88 with 2.20 intake...then you have a 71 J head.

The ports are the same...

exhaust manifolds are different...put headers on it if you want the best performance...

you need to raise the compression....KB243 pistons will get your compression back to 71 level....although the 71 340 is rated a 10.5 to 1 compression is it more like 9.5.....and with cast iron heads is probably the best you should have given today's gas....

 

[340plot]

73 340 heads are J heads....just replace 1.88 with 2.20 intake...then you have a 71 J head.

The ports are the same...

exhaust manifolds are different...put headers on it if you want the best performance...

you need to raise the compression....KB243 pistons will get your compression back to 71 level....although the 71 340 is rated a 10.5 to 1 compression is it more like 9.5.....and with cast iron heads is probably the best you should have given today's gas....

ok,great about the heads. would my local machine shop be able to do the bigger valves? oh, and the exaust manifolds. i had a few a bodies with headers, and i think they suck, cause every set i had on the cars would get crushed cause they sit so low to the ground. is there anything i can do with the stock ones?

 

[70aarcuda]

any GOOD machine shop should be able to install larger vavles...

there are two makers of headers that do not hang down ...

TTi and Headers by Doug

I have tti on my 73 340 duster.....they look as beautiful today as they did 5 yrs ago...

 

[70aarcuda]

this is what it looked like went i got it.....

 

[moper]

400 horsepower ia doable but you need to go thru the engine. As far as daily drivien, you could do it on the manifolds but it's easier (read as cheaper/better) to run them. Your '73 may not have had the 8 3/4. I've seen the 8 1/4s in them before and that wouldnt surprise me if you have one in it. The earlier engines are not very different. So to reach your level figure on a total rebuild, a little bit of head work, cam, intake, carb, etc. What is your realistic budget?

 

[340_833 dart]

'73 340 Darts had the 8.25" rearend.
All 340 automatic cars had the 727.
Pistons in the 340s were supposed to be 0.018" out of the hole. After my block was decked and squared the KB243 pistons are now 0.020" above deck.
I swapped the original 1.88"/1.60" J heads for 2.02"/1.60" O heads.
But, with the factory open chamber heads and 0.039" thick head gaskets, I still don't have quench. I guesstimate the CR at 9.8:1. That was the only thing I didn't measure when I was assembling the engine.#-o
The heads have stainless valves with a 3-angle valve job. They were pocket ported and gasket matched to the intake.
I'm running the Lunati Voodoo 60403 cam, Edelbrock Performer RPM manifold and Holley 750 cfm vacuum secondary carb, along with TTI headers.
If Desktop Dyno can be believed, the engine is around 410 horsepower and 390 ft lbs.
It is a fun car to drive on the street. Gas mileage stinks but, who cares? It's not a daily driver.

 

[340plot]

yea, it has the 8 1/4 in it, but i picked up a rolling 340-manual car that im taking the 8 3/44 and posi chunk out of, and cutting the hump out of it before i junk it. unless you know someone looking for a clear titled 71 340 car that needs minumal body work, but the interior is gutted also.