340 Cam

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Dan the man

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What is the actual duration at 0.050" of mopars 340 cam? The places that I've looked into give different answers, some say it's 208* intake / 214* exhaust, while others say it's 228* intake / 235* exhaust. I have a older mopar engine builder's manual and it said that factory cams are figured by multiplying advertised duration by .777 and performance cam's by .850. I thought that the 340 cam would be considered a performance cam since it was only in the 340 and the high performance 360's. Is the .850 for the purple shaft cam's only? I'm thinking about using a cam that's equivalent to the 340 in the 318. What compression ratio would I need? Thanks everyone.
 
eekvonzipper said:
What else are you doing to your 318? is it still a two-Barrel?
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Going to a 4 barrel carburetor, 650?. Headers, 2 1/4" dual exhaust. Is a x pipe helpful? The car is going to be a semi daily driver ( weather permitting). Mainly looking to improve performance, 300 horsepower at the flywheel is fine with me. I'm wanting better throttle response and low to midrange torque.
 
Yeah, I think the X-Pipe Helps with Low-End Torque some but it probably makes Tranny service a real bear...
Do some Compression testing first, If you have a stock engine with alot of miles and wear I'd be worried about Washing the Rings out of it.
 
The 2 340 cams you describe above sounds correct. They had 2 versions, one for the automatic transmission and one for the manual transmission. The one with the lower duration was for the automatic. 65'
 
Dan the man said:
What is the actual duration at 0.050" of mopars 340 cam? The places that I've looked into give different answers, some say it's 208* intake / 214* exhaust, while others say it's 228* intake / 235* exhaust. I have a older mopar engine builder's manual and it said that factory cams are figured by multiplying advertised duration by .777 and performance cam's by .850. I thought that the 340 cam would be considered a performance cam since it was only in the 340 and the high performance 360's. Is the .850 for the purple shaft cam's only? I'm thinking about using a cam that's equivalent to the 340 in the 318. What compression ratio would I need? Thanks everyone.
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Cam's weren't measured @.050 back then so specs you may find are a guesstimate. Use the search feature here. There are a dozen pages of threads that have 340 cam information.
 
Plymouth 65 said:
The 2 340 cams you describe above sounds correct. They had 2 versions, one for the automatic transmission and one for the manual transmission. The one with the lower duration was for the automatic. 65'
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That was only for 1968 340 cars. Does not apply to any other year.
 
CamCraft-factory hi-po cam specs.png
 
The early 68 4 speed 340's had a bigger cam. The 340 automatic specs were 268,276 .429,.444

For the manual cam they put the auto exhaust lobe on the intake and borrowed the 440 magnum exhaust lobe for the exhaust to end up with 276,284 .444, .453. Both auto and manual cams had 114 degrees lobe separation.
 
65 Cuda 340 said:
Can't remember - I saved it to My Documents quite a while back - but the name of the file is "Cam-Craft Factory hi-po cam specs."
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Camcraft catalogs are one of the sources that list durations at lift (.006/.004 etc) for those cams.
Cam 5214 671 may be a later version of the earlier cams or Camcrafts number?
Part number changes may have been just a subtle change in design.
 
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toolmanmike said:
@krazykuda has a lot of time and work into these specs. The information came from factory service manuals. Thanks Karl.
Factory V-8 Engine and Cam Specs by Year 1965-1975
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Those are gross duration figures, not duration at .050.

I would note that CamCraft's "advertised duration" figures for Mopar cams don't agree with Chrysler's own advertised figures. I'm thinking that CamCraft's "advertised duration" is using a different base lift to measure duration from than Chrysler did. I remember Chevy cams of the era had what looked like huge durations - 300 plus degrees - much more than similar lift Chrysler cams. But that's because - as I understand it - Chevy measure the duration of their cams at zero or near zero lift, while Chrysler measured their durations at (I believe) something like .006 lift. Going by memory, so I might have my numbers off, but there was a significant difference between the way Chrysler and GM measured their cams' durations.

Even Chrysler could play that game. There were a couple of Chrysler Corp. ads in the late sixties that bragged about the HP 440 cams having something like 284/292 duration, and some have thought this was a totally different cam, when in fact it was (I believe) just the regular hi-po 276/284 440 cam measured from a different starting point.
 

"Those are gross duration figures, not duration at .050."

Yes they are. Correct

Like I mentioned earlier, back in the 60's @ .050 specs weren't used. Any @ .050 specs are purely speculation unless a factory cam was found and measured. @krazykuda has worked on that project. May be he will chime in. I can see where advertised duration numbers can be big. Duration is the amount of time in degrees the valve is open. If you start measuring it at 0 or close to zero lift of course the numbers will be higher than at .050.
 
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65 Cuda 340 said:
CamCraft's "advertised duration" is using a different base lift to measure duration from than Chrysler did.
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They are.
65 Cuda 340 said:
Chrysler measured their durations at (I believe) something like .006 lift
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Chrysler's durations are tied to the ramp change on engineering drawings. @Wyrmrider helped establish that we need to use Camcraft and similar catalogs to get close to a duration at a lift.

Wyrmrider wrote:
"Chrysler has a unique yet consistent way of measuring duration. They take the blueprint point where the clearance ramp meets the acceleration ramp and add 4 degrees to the opening and 4 degrees to the close."
from what cam shaft are you running on the street

and
"340 HP CAM here you can compare MOPAR duration which is close to .008 with .004 data"
I think here .008 is at the valve, and am pretty sure .004 is SAE and therefore .006 at the valve for 1.5:1 rockers.

When I plugged those durations into Dynomation (which has to use .006 at valve), the hp and torque curves looked much closer to published dyno tests. 340 cam specs?
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Here's some 340, and 360 4bbl cam part numbers..
Chrysler
2899205 1968 Manual Transmission
2899206 1968 Automatic Transmission,1969-1975 340 & 360 with 4bbl
4214671 (1974- 1976 360 E58 package internet info. 360 Stock Cam Spec's.?)
4041998 1976-80 360 w/ 4bbl [E58 ?] in Shepard.

Other Chrysler LA HP/4bbl hydraulic FT cams almost certainly different:
4227879 1980-1987 318 4 bbl [E46 or E48? & Police pkg?]
4042000 1976 -79 360HP [Calif ? E56?]
 
65 Cuda 340 said:
There were a couple of Chrysler Corp. ads in the late sixties that bragged about the HP 440 cams having something like 284/292 duration, and some have thought this was a totally different cam, when in fact it was (I believe) just the regular hi-po 276/284 440 cam measured from a different starting point.
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That's probably correct. Using Wyrm's guidance -
276/284 is close to durations at .008" valve lift and
284/292 could be the durations at .006" valve lift

That's certainly plausible especially when considering the ramp rates.
 
Mattax said:
They are.

Chrysler's durations are tied to the ramp change on engineering drawings. @Wyrmrider helped establish that we need to use Camcraft and similar catalogs to get close to a duration at a lift.

Wyrmrider wrote:
"Chrysler has a unique yet consistent way of measuring duration. They take the blueprint point where the clearance ramp meets the acceleration ramp and add 4 degrees to the opening and 4 degrees to the close."
from what cam shaft are you running on the street

and
"340 HP CAM here you can compare MOPAR duration which is close to .008 with .004 data"
I think here .008 is at the valve, and am pretty sure .004 is SAE and therefore .006 at the valve for 1.5:1 rockers.

When I plugged those durations into Dynomation (which has to use .006 at valve), the hp and torque curves looked much closer to published dyno tests. 340 cam specs?
--------------------------------------------------------------------------------------------------------------------------
Here's some 340, and 360 4bbl cam part numbers..
Chrysler
2899205 1968 Manual Transmission
2899206 1968 Automatic Transmission,1969-1975 340 & 360 with 4bbl
4214671 (1974- 1976 360 E58 package internet info. 360 Stock Cam Spec's.?)
4041998 1976-80 360 w/ 4bbl [E58 ?] in Shepard.

Other Chrysler LA HP/4bbl hydraulic FT cams almost certainly different:
4227879 1980-1987 318 4 bbl [E46 or E48? & Police pkg?]
4042000 1976 -79 360HP [Calif ? E56?]
Click to expand...

Wow! That explanation of how Chrysler measured duration makes my head spin, but thanks for the info.
 
65 Cuda 340 said:
Wow! That explanation of how Chrysler measured duration makes my head spin, but thanks for the info.
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Maybe this will help.
Let's just look at the difference between measuring duration at a .006" valve lift versus .008" valve lift.
Imagine putting an dial indicator on an valve. Turn the engine until the valve moves up .006", then continue until its lifted .008"

If we magnify the begining of the lift, it looks like this.
upload_2022-2-26_16-41-39.png


The take away is that Chrysler cams at .006" have more duration than stated in the Chrysler books.

When comparing Chrysler cam durations to non-Chrysler cams, the closest equivalent will be durations given at .008
 
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I get that the closer to zero you start measuring duration, the longer the duration measure you're gonna get. But measuring from where the clearance ramp meets the acceleration ramp and then adding 4 degrees on both ends - never heard that one before. Interesting. Wonder why Chrysler did that? More accurate measure of effective duration? I.e., duration that actually contributes to airflow through the valves? Thinking that effective flow is practically zero during the clearance ramp?
 
We've discussed this in depth many times in the past. Chrysler was very ambiguous about how they measured camshaft specs because they didn't want me, you or anyone else to know. It was a proprietary decision. Much like a copyright.
 
You guys think Cs method of calculating adv duration is confusing!

How about Pontiac. Post-1965 hyd cams were measured at 0.002" valve lift on the opening side & 0.008-9" on the closing side. Have no clue as to how that rationale was arrived at....Using this nonsense, Pontiac rated it's biggest factory cam the RA4 as 308/320* adv duration. The numbers at 050 were 231/240*. The Comp 280* magnum cam has 280* adv duration & 230 @ 050.
There were some ridiculous adv numbers advertised [ pardon the pun ] back in the day to see who had the biggest...
How about the Herbert #70: 400* adv, 279 @ 050.
 
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