what about this one
best cam for a 340
- Thread starter polywideblock
- Start date
wyrmrider
Well-Known Member
here is a recent thread on 340 4 speed .325 gears with a emphasis on pleasure driving not hot rodding
https://www.forabodiesonly.com/mopa...-restoring-68-340-that-runs-on-91-oct.416141/
https://www.forabodiesonly.com/mopa...-restoring-68-340-that-runs-on-91-oct.416141/
rumblefish360
Well-Known Member
It is very similar intake duration wise to your other (3rd) choice @ 224 which I shyed away from because of the gear and tire size combonation. Like I said in my second choice, it may take some foot to clutch pedal finesse to get going. The cams rpm range starts a little higher up than what would make for a good driving combination.
Once you start moving the car, somewhere around 1900-2000 everything starts catching on and working well. While I listed the rpm ranges a bit above what Comp has listed, it may have a slight curve beyond what they stated, it is the overall package that has to be looked at.
The cars gear ratio & tire size I have stated but also the cars weight and size. Being a B body, a very similar set up to my ‘73 E body 340/4spd that I have had for the last 32 years under multiple changes of stock to race parts from stem to stern. Finding the sweet drivers combo with the 3.23 gears it was born with always lead to a smaller cam.
The smallest cam I had was a Crane 216/228-.454-.480-112 in it. I had at the time the same gear ratio and tire size as you have now. I had to use mine as a daily driver for work in and out of NY city. (A 30 mile car clogged rush hour one way trip)
After a tire diameter reduction, (235/60/15 - 26 inches) the drive abilty was enhanced with an easier roll off the line and not so much clutch work to get going.
If your looking for a more performance oriented ride 1 step above stock, go for it. I tried to keep the cams listed in a operating range with consideration of the current combo of the car and the car itself in mind. The centerlines are at 110, in which that should provide the typical muscle car choppy idle.
In my 4spd Cuda I have run the 275/60/15’s with a cam duration @ [email protected] and a 4.10 gear. I would side step the clutch at 3500 rpm’s as that was about the best area to have the car get up and GO! Around town, it was crappy.
rumblefish360
Well-Known Member
A thread gone amok
wyrmrider
Well-Known Member
OK post 4 we find out the car is a 4 speed
Find out it's a 71 in a heavy Roadrunner
post 6 rumble asks some key questions
rear gears, low gear in 4 speed, tires, weight, cruise rpm, power brakes
post 7 rumble questions if low compression engine- we do not know
rumble says “in general” and in general he is correct- but it depends on the Duration as much as the “centerline” and I can't tell if he means centerline the way Mopar Performance uses the term i.e. Lobe Centers or if he is commenting on the installed intake centerline
Looks like he is referring to the ground in lobe center
post 12
Hughes is not a cam company but good advice
post 15 we find out cranking compression 157-160
post 16
caveat on gears on the manual and gears and converter on the automatic
rumble asks if the motor is a stock 71 (or has it been rebuilt with rebuilder pistons)
https://www.hotrod.com/articles/bad-mopars-340-beat-ford-chevy-shocking-new-data/
why the carb change
J heads with 2.02 valves are stock. The stock carb is a Carter Thermoquad rated at 800 cfm.
post 17 3.23 gears
post 18
270H obsolete crap you are better off with a stock 340 cam
post 19 rumble nails it on the 270 @006 size cam
rumble makes some suggestion is post 20
do we know if he has headers or stock exhaust and did 71 have the good er 340 cast exhaust still?
XE262H still do not know compression but best so far if stock Intake and exhaust closes 57ABDC
IMHO 274dual energy is a gimmick and is worse than 270H intake closes 64ABDC
will loose a lot of dynamic compression
256-262 Lunati looks better than 270 or 274 comp's intake close would be about 54 ABDC
262/268 lunati much better choice than XE268 comp
do need to nail down the valve springs and how much lift can be had keeper to stem seal
what rumbel said read it again
Finding the sweet drivers combo with the 3.23 gears it was born with always lead to a smaller cam.
275 with 4.10 gears= Around town, it was crappy.
So stock heads? Headers?
Looks like the Lunati or Howard found in the gone amok thread would work here too
exhaust duration and lobe centers would depend on compression and exhaust efficiency
Find out it's a 71 in a heavy Roadrunner
post 6 rumble asks some key questions
rear gears, low gear in 4 speed, tires, weight, cruise rpm, power brakes
post 7 rumble questions if low compression engine- we do not know
rumble says “in general” and in general he is correct- but it depends on the Duration as much as the “centerline” and I can't tell if he means centerline the way Mopar Performance uses the term i.e. Lobe Centers or if he is commenting on the installed intake centerline
Looks like he is referring to the ground in lobe center
post 12
Hughes is not a cam company but good advice
post 15 we find out cranking compression 157-160
post 16
caveat on gears on the manual and gears and converter on the automatic
rumble asks if the motor is a stock 71 (or has it been rebuilt with rebuilder pistons)
https://www.hotrod.com/articles/bad-mopars-340-beat-ford-chevy-shocking-new-data/
why the carb change
J heads with 2.02 valves are stock. The stock carb is a Carter Thermoquad rated at 800 cfm.
post 17 3.23 gears
post 18
270H obsolete crap you are better off with a stock 340 cam
post 19 rumble nails it on the 270 @006 size cam
rumble makes some suggestion is post 20
do we know if he has headers or stock exhaust and did 71 have the good er 340 cast exhaust still?
XE262H still do not know compression but best so far if stock Intake and exhaust closes 57ABDC
IMHO 274dual energy is a gimmick and is worse than 270H intake closes 64ABDC
will loose a lot of dynamic compression
256-262 Lunati looks better than 270 or 274 comp's intake close would be about 54 ABDC
262/268 lunati much better choice than XE268 comp
do need to nail down the valve springs and how much lift can be had keeper to stem seal
what rumbel said read it again
Finding the sweet drivers combo with the 3.23 gears it was born with always lead to a smaller cam.
275 with 4.10 gears= Around town, it was crappy.
So stock heads? Headers?
Looks like the Lunati or Howard found in the gone amok thread would work here too
exhaust duration and lobe centers would depend on compression and exhaust efficiency
rumblefish360
Well-Known Member
This question towards myself? Headers, Hooker Super Comps @1-3/4, Edelbrock heads.
The 274 Dual Energy Comp cam you labeled gimmick is not. Works fine.
I mentioned centerline as described in the manufactures pages.
He has exhaust manifolds.
Why do you think the he changed the carb? He could have gotten the car that way with the rpm intake under it. Not all J heads are 2.02, they also may not be stock. You assume to much.
How so? Please describe.
You also need to learn how to make use of the quote feature.
You also should not be splitting hairs (again) over the most minor details flaming big power.
rumblefish360
Well-Known Member
When monies allow, swap to a RPM and feel a positive impact on the additional torque with a no loss on HP. You will thank me after the swap.
Signed, the been there done that and most happy with it!!!!
69b3rt
Well-Known Member
I have been contemplating going to that Edelbrock Performer RPM combo for a while. The intake seems even taller than the TorquerII. I like hiding everything under stock air cleaner.
I'm going with your first choice it seems to be what I'm after, a bit hotter than stock but not over the top
wyrmrider
Well-Known Member
That's sub prime rumble, you can do better
so at the last minute, I went with the above XE268H #21 instead K20-223-3
but included this as an upgrade
but included this as an upgrade
wyrmrider
Well-Known Member
They are both old 1977 vintage chevy profiles
pick one with the 262 duration and the 268 lift
pick one with the 262 duration and the 268 lift
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