71 cuda 340 carb and cam

[culp71]

Hello

I'm rebuilding a 70 340 w 4 barrel (J heads / forged crank) back to "close as possible" to original specs for a 71 cuda.
Of course slight boring will be done to get cylinders round again, but I want it to be just like the day it was built.

? does anyone have info for the 340 (4 barrel "shaker" LA engine) original cam specs.?
(duration, lift, center line, overlap etc.)

thanks

[cudabob496]

http://www.forabodiesonly.com/mopar/showthread.php?t=53607

[AussieMark]

Comp Cams grind # 268AH-10 part # 20-309-4 I am planning on using this cam as well when I rebuild my 1970 340 a good choice because we know how well it works and you don't need special springs or the cylinder head machining that goes with them, the springs Comp Cams recommend will fit no hassles.

[AussieMark]

There is another cam worth a look part # 20-233-3 grind # XE68H just found it on the website so close to the original one yet is slightly more everywhere and the powerband is slightly wider coming in 200 rpm earlier comes in a kit with the lifters and timing kit part # SK20-223-3.

[culp71]

alright, all good info thanks. I've got the cam all figured out.

my next question is what was the cfm on the original carb (340 w 4 barrel/shaker), additionally which should be used
between the Edelbrock thunder series AVS or Edelbrock performer carb?

which is closest to the original?

thanks

[anlauto]

Why not run the original Thermoquad ?

[crash340]

Agree, dont be put off by the TQ, its not that hard to set up and there are some great youTube series on setting them up and tweaking them.

[Chryco Psycho]

Personally I would match up the duration specs for the cam to the Lunati VooDoo series
This cam matches exactly to the duration spec for the auto 340 but has more lift with over .500 compared to the original .444 lift
 http://www.summitracing.com/int/parts/lun-10200703lk.
 71 340s had the TQ , that is what I would use over any of the Eddy series carbs , the AVS Thunder carbs are closer to the original carbs used 68-70 & are more tunable than the AFB type which overall Mopar almost never used on anything except the Hemi

[AussieMark]

Chryco when you go any bigger on the cam they seem to recommend a double valve spring which will need the valve guides to be machined and I am just wondering (for my own application) is it really worth the extra effort to gain an extra .030"lift I am thinking of the extra load on the valve train (parasitic loss) caused by the heavier springs and with standard O or J heads will it increase the flow enough to justify the additional lift? thanks Mark

[Chryco Psycho]

You would have to check with Lunati but I believe a heavier single spring should work OK & you need to trim the top of the guides too but lift is basically free extra flow so the engine shoudl run similar to a stock cam but make more power , but I have always ported the heads as well to maximize the benefits of both the heads & cam working together , you could always step down 1 cam to the 702 grind giving you a bit more bottom end to midrange power with great idle vacuum etc for power brakes .
 I have this disease where I get caught up in the reality of if you are spending all of the $$ anyway why not maximize the potential of all the parts being used especially when a lot of the parts cost the same or very little more to get the most outof the final package .... silly me !!

[73restomod]

I would go with the lunati as well, and find a nice beehive valve spring setup to run it. It will make the most of what you have, and cost should be kept low because no hardcore machine work should be needed to do it.