340, camshaft choice for a 50 year old motor......

[bandit67]

Guys, just found out the cam I have for my 340 build is not for a Mopar. So, cam needed. I have assembled a good candidate choice I think for this build . It is 1970 340 with windage tray, steel crank, and j heads.....2.02 valves I think. I plan to stay with the stock converter, no high stalls, and am looking for killer torque and stay in the 1500 to 5800 rpm band. I Like 108 to 110 lobe centers but not sure if these heads like split pattern lifts or single pattern lifts. I have only run hydraulic flat tappets but maybe a roller cam if one will work with the stock valve train? New springs were installed by my machine shop but they were just performance replacements...nothing heavy. New carb and intake coming and maybe headers in the future, thanks for any opinions.....

 

[69a100]

What's the numbers on a stock cam, lift/dur. for a 340? Take those numbers and do not go beyond 10% more then stock duration, and not more them .050" lift over stock and you will have one strong street cruzer that can use a stock converter. These are words from from the guru Steve Dulcich that he told me this when I was looking for a cam upgrade.
Stick within those parameters and you'll be fine. Good Luck

 

[kramer]

On street motors with stock type stall torque convertors and especially if your going to stay hp exhaust manifolds I would keep lobe seperation numbers in the 112 to 114 range it tends to flatten out the torque curve and better low end torque, it won't give you the peak hp and torque numbers but it helps in streetability.

 

[toolmanmike]

Then call Jim at Racer Brown, tell him what you have and what you want and let him choose your lobes for you.


Make the call to Jim. Call him after 2 PM EST and he can help you with the best cam for you.

 

[PRHeads]

Comp 268H

 

[Derwud]

I love the 340 stock HP cam..

But that is great info here, "On street motors with stock type stall torque convertors and especially if your going to stay hp exhaust manifolds I would keep lobe seperation numbers in the 112 to 114 range it tends to flatten out the torque curve and better low end torque, it won't give you the peak hp and torque numbers but it helps in streetability"

 

[toolmanmike]

Lots of 340 cam discussion on FABO. https://www.forabodiesonly.com/mopar/search/78668404/?q=340+cam&o=relevance

 

[bandit67]

Thanks Guys, and Toolman for all those thread links. Got a good idea of the direction I wish to head in but need to do some actual hard data numbers;ie Comp. Ratio, before I buy. I do wish to learn more but do think LS in the 112-114 will be better for me than the 110-108 range. Sounds like Jim is the go to guy to tie it all together.....thanks

 

[rumblefish360]

What is your gear ratio, tire size & what transmission are you running.

FWIW, any cam with a duration @ .050 larger than 218 would be best if the converter was changed to a higher stall rating. While a quality converter would drive around like a stock one would and shine under a mashing or the go pedal, the expense (and work) can be avoided.

The 340 had a higher stall converter than the normal people movers had. You can get away with a little more cam if the gear ratio and tire size isn’t out of line with the new cam choice.
(Like what PRH suggested.)

Going to a roller is not just about laying the pipper the cash and slam dunking the expensive set up in and go.

 

[wyrmrider]

racer brown- good choice
comp under 274HL not so good Lunati voodoo is 2 generations later design according to designer UBHarold
340 stock cam is way obsolete really long duration for little lift
big problem is you did not give how much compression you have- makes a big difference
book says 10.5 but really more like 9.5 unless someone has changed the pistons along the way
stock heads or milled a bunch bone stock heads cannot make use over 450 lift- slightly more with a modern valve job and a mild bowl blend
you most likely have the hp converter
even bigger question is how do you want to drive it
answer rumble's question

hard to compare Mopar timing with anything else - you are close comparing to Engle or Racer Brown
that 268 mopar duration is more like almost 290 crane degrees

 

[bandit67]

Car this is going in , 73 Challenger, converter, rear gear ratio, 727...no clue if original or not. Car was originally a 340 motor. Pistons are KB 243 s which state 10.2 c. r. with my heads. Heads were in good shape and need only slight surfacing. .39 gasket dropped comp. ratio somewhat.,.14 or .16 above deck height, I think. Tire size, not much more than original..

 

[wyrmrider]

so a higher compression 340 not 73 compression
hyd cam
you need some help choosing
call racer brown (eves)
pm dart19666 at crower on this board
the only catalog cams to look at are lunati download the catalog
you are the only one to pick your rev range
but remember the converter caveat above-or you will be on the converter/ gears treadmill
watch out for suggestion on how to get bracket racing max horsepower
you need a big fat torque curve
fill this out
http://jonescams.com/street-performance/

 

[Bighead440]

We put a Lunati factory performance 340 grind cam in this '67 Belvedere sedan, it is a factory 273 car with a 1968 340, positive deck pistons and steel crank. It's pretty healthy, with 232/242*@.050" lift on a 112*LSA, but it has spring friendly .462/.473" lift. We advanced it 4* and it pulls pretty dang hard!! You'll be needing 3.55+ on gear and a 2500+stall converter for sure.

 

[wyrmrider]

factory performance 340 grind cam
232/242*@.050" lift
does not compute or you have a funny definition of factory
what cam series? part number?
thanks for your observations

 

[toolmanmike]

We put a Lunati factory performance 340 grind cam in this '67 Belvedere sedan, it is a factory 273 car with a 1968 340, positive deck pistons and steel crank. It's pretty healthy, with 232/242*@.050" lift on a 112*LSA, but it has spring friendly .462/.473" lift. We advanced it 4* and it pulls pretty dang hard!! You'll be needing 3.55+ on gear and a 2500+stall converter for sure.

I can hear the 4° advance in the lope. Sounds good.

 

[wyrmrider]

First where did you get the 10.2
most 340's with flat top pistons and a fel pro thick gasket are closer to 9:1
NHRA spec was for positive deck +.002 (if I remember without looking it up- so were 383 HP's)
a little theory here
the stock exhaust does not like overlap
\which is why it was suggested to keep your lca wide
the Lunati Voodoos- the shorter ones --are 112 which should work
108 0r 110 not so much
so pick the larger voodoo with the 112 lca
or you may have to go custom
The Crower 281 HDP works and is a catalog cam ( if you want a hot cam which you say you do not)
go over to fabo and PM Dart19666 about it but it's a lot bigger than the mentioned Voodoos
otherwise I can't think of a shelf grind

 

[Bighead440]

factory performance 340 grind cam
232/242*@.050" lift
does not compute or you have a funny definition of factory
what cam series? part number?
thanks for your observations

https://www.lunatipower.com/factory...-cam-lifter-kit-chrysler-273-360-298-308.html

 

[Bighead440]

First where did you get the 10.2
most 340's with flat top pistons and a fel pro thick gasket are closer to 9:1
NHRA spec was for positive deck +.002 (if I remember without looking it up- so were 383 HP's)
a little theory here
the stock exhaust does not like overlap
\which is why it was suggested to keep your lca wide
the Lunati Voodoos- the shorter ones --are 112 which should work
108 0r 110 not so much
so pick the larger voodoo with the 112 lca
or you may have to go custom
The Crower 281 HDP works and is a catalog cam ( if you want a hot cam which you say you do not)
go over to fabo and PM Dart19666 about it but it's a lot bigger than the mentioned Voodoos
otherwise I can't think of a shelf grind

I have seen the early 340s ('68-71) with positive deck. They can get a little sensitive on detonation with X or J heads and pump gas. A quick way to pep-up a zero to negative deck ('72&3) 340 is to put a closed chamber head on, like aftermarket or a magnum head. The early M1 dual plane Magnum carb intake has the centered water outlet and looks similar to the original unit. We upgraded a '70 Challenger 340 that had been converted to low compression with TRW forged '72-up replacement pistons (to alleviate spark knock issues) at some point, by adding Magnum heads and China "air-gap" intake, removing X heads and an LD340. Same headers/gear/converter and it was like we put a 4" crank in it!! It had the Melling 340 resto cam, I can't remember the "SPD" etc. part #, but I think it was like 210/222* @.050"with .440"ish lift.

 

[toolmanmike]

https://www.lunatipower.com/factory...-cam-lifter-kit-chrysler-273-360-298-308.html

That Lunati is a bit big compared to the stock 340 cam specs I think.
'68-'73 340 .430/.444 lift 268/276 duration...the '68 340 with manual trans. was .444/.453 lift .276/.284 duration...

 

[Bighead440]

That Lunati is a bit big compared to the stock 340 cam specs I think.
'68-'73 340 .430/.444 lift 268/276 duration...the '68 340 with manual trans. was .444/.453 lift .276/.284 duration...

Yes, I agree 100%. I don't grind cams, I just buy them based on specs to hopefully function well and perform. This one does just that, especially since a '67 Belvedere wouldn't have had a 340 anyway...