Question about Camshaft specs

[Mrbill426]

Are stated camshaft spec numbers, specifically "duration" measured from a particular point in valve opening or is total time the the valve is of its seat?
I am trying to decipher this "custom ground" cam that the lift looks right but I am confused on the duration... supposedly in the neighborhood of 276/284...  Can someone help?

[MoparCarGuy]

The cam card shows it is .444 INT/ .453 EXH lift and duration is 212° Intake/ 224° Exhaust @ 0.050 (fifty thousands lift).
Who is the cam manufacturer? Many aftermarket camshafts are not ground to take advantage of the larger Mopar lifter size of .904".

Here is some excellent info on real Chrysler cams.http://www.hughesengines.com/TechArticles/1camshaftfrequentlyaskedquestions.php

[Mrbill426]

@MoparCarGuy so no way do those numbers work out to  276/284 duration's?  It says @.050" but I wondered if it was just measured differently.
Also are Mopar cam lobes wider than than others, is that what your mean?
Thanks!

The cam card shows it is .444 INT/ .453 EXH lift and duration is 212° Intake/ 224° Exhaust @ 0.050 (fifty thousands lift).
Who is the cam manufacturer? Many aftermarket camshafts are not ground to take advantage of the larger Mopar lifter size of .904".

Here is some excellent info on real Chrysler cams.http://www.hughesengines.com/TechArticles/1camshaftfrequentlyaskedquestions.php

[DeathProofCuda]

276/284 is the "advertised" duration for that cam.  Advertised duration is pretty much meaningless when comparing cams from one manufacturer to another, so you really want to be paying attention to the duration at 0.050".  That looks to be a relatively mild cam.  What are you using it for?

[MoparCarGuy]

@MoparCarGuy so no way do those numbers work out to  276/284 duration's?  It says @.050" but I wondered if it was just measured differently.
Also are Mopar cam lobes wider than than others, is that what your mean?
Thanks!

No, read the questions and answers on the link I posted for you. The ramps on the cam lobes can be much more aggressive when using the larger .904 lifter size but the cam manufacturer has to take advantage of that.

[Mrbill426]

@DeathProofCuda unless I am blind I don't see that advertised anywhere on the card so that is what is throwing me off.  I asked for a cam with  444/453 int/exh lift, and  276/284 degrees duration, or what I understand to be a early 340 cam for a manual transmission.  The lift on the card matches but not the duration.  Now maybe Mopar's cam was actually 212/224 @ .050???  But I cannot find that info.
It's a '72 340 with stock rebuilt heads, stock exhaust manifolds, an LD340 intake, and 10.5-1 forged pistons.  Just a mild upgrade to a smogger.

276/284 is the "advertised" duration for that cam.  Advertised duration is pretty much meaningless when comparing cams from one manufacturer to another, so you really want to be paying attention to the duration at 0.050".  That looks to be a relatively mild cam.  What are you using it for?

[DeathProofCuda]

@Mrbill426 I'm no cam expert, and an even less familiar with small block cams but consider these two examples of cams that I think would be in the ballpark of what you are looking for.

Lunati considers this their version of the 340 high performance cam:
- Advertised duration 298/308
- Duration at 50 232/242
- Lift 462/473
- LSA 112
https://www.lunatipower.com/factory-performance-hydraulic-flat-tappet-cam-chrysler-273-360-298-308.html

Here's one of the Mopar Purple Shafts with similar lift to yours:
-Advertised duration 268/272
-Duration at 50 228/231
-Lift 450/455
-LSA 110
https://www.manciniracing.com/hyd268272dur.html

Again, not a smallblock expert here, but the 212/224 duration at 50 for your cam seems a bit low to me for a performance cam.  

Maybe someone else more qualified will chime in here.

[DeathProofCuda]

Here's a thread from the FABO site discussing the specs for the stock 340 cam.  Seems like the duration at 50 specification for yours is correct.

https://www.forabodiesonly.com/mopar/threads/340-cam-specs.53607/

[RzeroB]

"Advertised" duration vs duration at .050" lift. "Back in the day" advertised duration was all that was used. It measured the start of duration at the first indication of lift and continued until the last indication of lift. A lot of things could vary the first visible indication of lift ... and the end of it. Thus the more accurate method of measuring duration beginning, and ending, at .050" lift became the new standard. It's almost impossible to correctly compare duration of a cam that has only "advertised" duration listed to one that is measured at .050" lift ... apples and oranges if you will.

[Mrbill426]

@DeathProofCuda Numbers swimming in my old brain  ..... so taking back what you said a bit earlier about it being "low" it appears I got what I asked for?
Thanks

Here's a thread from the FABO site discussing the specs for the stock 340 cam.  Seems like the duration at 50 specification for yours is correct.

https://www.forabodiesonly.com/mopar/threads/340-cam-specs.53607/

[Mrbill426]

@DeathProofCuda and both have a duration @50 much lower

@Mrbill426 I'm no cam expert, and an even less familiar with small block cams but consider these two examples of cams that I think would be in the ballpark of what you are looking for.

Lunati considers this their version of the 340 high performance cam:
- Advertised duration 298/308
- Duration at 50 232/242
- Lift 462/473
- LSA 112
https://www.lunatipower.com/factory-performance-hydraulic-flat-tappet-cam-chrysler-273-360-298-308.html

Here's one of the Mopar Purple Shafts with similar lift to yours:
-Advertised duration 268/272
-Duration at 50 228/231
-Lift 450/455
-LSA 110
https://www.manciniracing.com/hyd268272dur.html

Again, not a smallblock expert here, but the 212/224 duration at 50 for your cam seems a bit low to me for a performance cam.  

Maybe someone else more qualified will chime in here.

[Mrbill426]

@RzeroB, thanks so that stock cam advertised number is from the moment the valve moves till it is back at rest on its seat?

"Advertised" duration vs duration at .050" lift. "Back in the day" advertised duration was all that was used. It measured the start of duration at the first indication of lift and continued until the last indication of lift. A lot of things could vary the first visible indication of lift ... and the end of it. Thus the more accurate method of measuring duration beginning, and ending, at .050" lift became the new standard. It's almost impossible to correctly compare duration of a cam that has only "advertised" duration listed to one that is measured at .050" lift ... apples and oranges if you will.

[DeathProofCuda]

@DeathProofCuda Numbers swimming in my old brain  ..... so taking back what you said a bit earlier about it being "low" it appears I got what I asked for?
Thanks

Here's a thread from the FABO site discussing the specs for the stock 340 cam.  Seems like the duration at 50 specification for yours is correct.

https://www.forabodiesonly.com/mopar/threads/340-cam-specs.53607/

Correct, sorry for creating any confusing.  It looks like you got what you asked for.

[DeathProofCuda]

@DeathProofCuda and both have a duration @50 much lower

@Mrbill426 I'm no cam expert, and an even less familiar with small block cams but consider these two examples of cams that I think would be in the ballpark of what you are looking for.

Lunati considers this their version of the 340 high performance cam:
- Advertised duration 298/308
- Duration at 50 232/242
- Lift 462/473
- LSA 112
https://www.lunatipower.com/factory-performance-hydraulic-flat-tappet-cam-chrysler-273-360-298-308.html

Here's one of the Mopar Purple Shafts with similar lift to yours:
-Advertised duration 268/272
-Duration at 50 228/231
-Lift 450/455
-LSA 110
https://www.manciniracing.com/hyd268272dur.html

Again, not a smallblock expert here, but the 212/224 duration at 50 for your cam seems a bit low to me for a performance cam.  

Maybe someone else more qualified will chime in here.

No, both of these cams have higher (longer) duration at 0.050" than your cam.

[Mrbill426]

@DeathProofCuda yep my type-O there    sorry.

@Mrbill426 I'm no cam expert, and an even less familiar with small block cams but consider these two examples of cams that I think would be in the ballpark of what you are looking for.

Lunati considers this their version of the 340 high performance cam:
- Advertised duration 298/308
- Duration at 50 232/242
- Lift 462/473
- LSA 112
https://www.lunatipower.com/factory-performance-hydraulic-flat-tappet-cam-chrysler-273-360-298-308.html

Here's one of the Mopar Purple Shafts with similar lift to yours:
-Advertised duration 268/272
-Duration at 50 228/231
-Lift 450/455
-LSA 110
https://www.manciniracing.com/hyd268272dur.html

Again, not a smallblock expert here, but the 212/224 duration at 50 for your cam seems a bit low to me for a performance cam.  

Maybe someone else more qualified will chime in here.

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No, both of these cams have higher (longer) duration at 0.050" than your cam.
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