Oldiron440
Well-Known Member
This 340 needs more cam and a 750 carb, that thing should be pulling like a M’Fr at 6000-6500.
How to get 400 hp out of 1971 340 .30 over
- Thread starter Jays71 demon
- Start date
-
The easiest and most cost effective way is to build a stone stock 71 and back 340 with forged pistons and put a 150 plate shot on it.
junkyardhero
Well-Known Member
if you extrapolate the data from the dyno test, it appears that each "bolt on" results in a 20hp gain (approx)... the 340 is rated at 275hp and we've seen 320hp in "stock" dyno tests so let's split the difference and call it 300.
add an intake, headers and carb you're at 360. throw in a reasonable cam and there's 380. i'd wager to guess roller rockers, springs, and a sightly more aggressive cam has you sitting at 400.
all of that without touching the heads or running some wild compression number.
yeah, you can make 400 with 318 but it's all about compression and heads. with a 340 you already have that in place, so working with that potential should easily send it over 400 all day.
add an intake, headers and carb you're at 360. throw in a reasonable cam and there's 380. i'd wager to guess roller rockers, springs, and a sightly more aggressive cam has you sitting at 400.
all of that without touching the heads or running some wild compression number.
yeah, you can make 400 with 318 but it's all about compression and heads. with a 340 you already have that in place, so working with that potential should easily send it over 400 all day.
It boils down to the sum of parts, going to need some head work to reach an honest 400.
It can be done with over the counter parts but you will need to open your wallet.
Most of the 340's with subpar factory heads are running well under 400.
It can be done with over the counter parts but you will need to open your wallet.
Most of the 340's with subpar factory heads are running well under 400.
The one place I’d argue is that, where do you find a stock as delivered 340 from ‘71 & down with the high compression pistons till running around today in good shape?
I think it’s a load of bologna because (IMO!) they all need to be rebuilt.
Initially I believe this is true but the fun factor has to wear on you over time. $$$ Especially if you are heavy footed. I’m sure someone has done the math. Spray ain’t cheap.
I have one
68 340 orig rings bearings
refreshed top end weiand stealth 650dp unilite 218 218 454 110 in 106 3.91sg tf-2 727
102k on the bottom end 169 psi cranking compression
junkyardhero
Well-Known Member
i was assuming that one would be starting with a 10.5:1 bottom end on a fresh build and then working toward 400 from there, not slapping parts on a wore out 55yr old motor.
ir3333
Well-Known Member
These guys a paid by the manufacturers whose parts they advertise. Here's Comp's own honest dyno of a 9.0:1 350 with good Dart heads, the XE268 and headers. Have a look!
junkyardhero
Well-Known Member
by all accounts, this is the same motor that you've raced, changed cams on and shot nitrous at?I have one
68 340 orig rings bearings
refreshed top end weiand stealth 650dp unilite 218 218 454 110 in 106 3.91sg tf-2 727
102k on the bottom end 169 psi cranking compression
*raises eyebrow*
Ive never sprayed this motor
i sprayed a 68 dart 270 318 340 heads hemi cam torker door stop 650 dp 3.23s
Also sprayed a70 duster 340 243@50 gk cam same torker door stop same 650 dp carb same unilte 3.23s
This motor came out of 68 gts i raced@80k miles ran 14.3@97 plus all stock 3.23s ended up being junked
That motor is in my 67 gt vert now
any more questions smart ***?
junkyardhero
Well-Known Member
pardon my conflating the facts, what with all your posts being so easy to decipher.
Yeah go with that now the you look a fool
Pay attention never said i sprayed a gts or 67 gtjust a dart 270 and 70 duster
clown
junkyardhero
Well-Known Member
if you wish to insult me i would much prefer if you did so using complete sentences, and maybe some grammar. or at least something that passes for the english language.
shocking revelation: i don't keep a detailed dossier on the History of a-bodyguy, facts V1
honestly, all you do is regurgitate some numbers salad that revolves around 13.0, headers, 340, torker, 150 shot, and double pumper. so you can see how somebody as simple as yours truly could easily become confused.
anyway, respectfully, go fart in a phone booth.
You ran your mouth and you got flushed be a man dont pass the the buck.
Whats this thread about ?
You want to try and call me out on BS you have no chance grow up.
Find the ignore button if you dont like my responses Dummy.
junkyardhero
Well-Known Member
what ever you say, pal.
i hope this exchange made you feel better about yourself; you obviously need that.
All it shows is you questioned my honesty i put you in your place for trying to do so.
You reacted like and immature punk.
That is all it shows.
junkyardhero
Well-Known Member
you sure showed me gramps! guess i owe you the two bits i got from mowing lawns yesterday after school!
you posted suspect anecdotal data, without context and counter to your other posts. i thought that was interesting and made mention of it.
i didn't question your honesty, i didn't call you names, and in fact i did note that after you came with the information to correct me that it was confusing.
so what, you think you really showed me? all you showed was that you're the immature punk who flipped out when you thought somebody questioned their honesty and started calling names. real class act with that, my dude.
and that's the tale of the tape right there.
[apologies to the commentariat, we now return you to the regularly scheduled programming of how to attain 400hp]
Trust me, he's neither the fool, clown or dummy.
Ode to the mighty 340, just add a cam, LD 340, headers and viola 400 hp. ....
....
doogievlg
Well-Known Member
I’ve heard a lot of small block guys say their car “should make 400 hp”. I think some folks need to recalibrate their denim dyno.
FYI OP, I have a similar build to yours but in a 360. Flat tops, RPM Intake, cam, and 750 DP. I made 413 hp / 430 ft lbs.
I followed your build, you forgot to mention the edelbrock heads.
doogievlg
Well-Known Member
lol yea that’s a big part to leave out. My bad.
-
