looking to rebuild my 340

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gniknayrb18

gniknayrb18

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i have a 71 340 that i wanna deck out in pretty much all edelbrock. not real sure if this is a good way to go or if something else would work better. what are your guys opinions with heads and intakes and cams....im not wanting to bore anything out. so tell me what you think
 
Tons better stuff out there than the Edelbrock cam line, but their heads and intakes are nice. Also, boring doesn't depend on "want" it depends on "need".
 
It's a 40 year old motor it might need to be bored just be prepared for that.
This is a thread by MRL that the 340 motor made 470 HP and 410(?) TQ. Sounds like it might be what you're after. Like MRL motor, mine is also a hyd roller cam with eddy closed chamber heads. His cam is a tad smaller than mine (mine is @ 50, 231/239 .535"/.550") but mine is 30 over and his block was 40 over.
 
its just weird my 340 has a street demon intake on it with a street demon carb and i floor it and it just doesnt take off like it should.....my 5.9 cummins is much quicker and that doesnt seam right to me it has a cam in it just not sure what all they did to it before i got it...put it this way i use to own a 77 formula 400 with a sb 400 and muncie 4 speed it had 6x heads a torker 2 intake and a 750 eddy carb and that thing would scream and light them up whenever i wanted
 
my 340 has headers on it with dual exhaust with purple hornets and all new piping just seams like its starving for fuel or over fueled and im not real familiar with the holley. but i know this has a cam in it and i just dont know whats going on with it.
 
What transmission you using and what rear gear ratio you using?
 
ok i guess my question is what is a good nasty sounding cam that i could replace in it... what are some good heads that are for street but will give me a good compression rate... and im pretty set on the intake and carb....going for the eddy air gap rmp and a 650 thunder series avs or a 750 avs
 
well im currently running a stock rear end ...7 1/4 but looking at a 8 3/4 that has been shortened....ive been told to stay from the rear end that im looking at but i honstly think it might be worth it
 
and i have a 727 in it that was rebuilt....the car had a slant 6 with a manual transmission and the guy i bought it from put a 340 and a 727 with an aluminum drive shaft and the exhaust but i cant even get this thing to spin the tires
 
gniknayrb18 said:
its just weird my 340 has a street demon intake on it with a street demon carb and i floor it and it just doesnt take off like it should.....my 5.9 cummins is much quicker and that doesnt seam right to me it has a cam in it just not sure what all they did to it before i got it...put it this way i use to own a 77 formula 400 with a sb 400 and muncie 4 speed it had 6x heads a torker 2 intake and a 750 eddy carb and that thing would scream and light them up whenever i wanted
Click to expand...

could be several things slowing it down... one or two of the following would hurt ya:
low stall converter
low compression (what year is the 340 block?)
kickdown not adjusted right for the trans
carb not set up for the combo
vacuum leak somewhere so carb not performing like it should
ign timing out of adjustment

if you look at the spark plugs and tell us how they look it might give us some ideas.
 
Do what you must on the rear axle but you've been given good advice on it. You've been warned. You could buy a complete ready to bolt in unit for far less what it will take to buy that one and get it ready to bolt in your car.
 
is this a good cam or just a standard one and i planned on picking that rear end up today but took your advice and let it go
 
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