Cam overlap

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dave ellis

Old guys
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I have a can with 12° of overlap at 50. Anyone have a formula to figure out the normally advertised duration? It's a Hughs cam. Duration is given at .006".
 
I don't think you have enough info. Is there not a part number on the cam?
 
You can figure it out if you have the intake and exhaust lobe centerline and the duration of both lobes.
 
.....
The generic formula Mopar gave was advertised x .850, to get @.050, won't work for anything else......& wasn't exactly correct for the PurpleShafts either depending on the grind......
[email protected] on a 112LSA is 12deg [email protected]....... how many more do You want...:poke:
 
Adv duration numbers vary among cam companies & the lobe design itself. Crane used 0.004" tappet lift, Comp 0.006", Ultra Dyne [ Bullet ] 0.0045".
 
Bewy said:
Adv duration numbers vary among cam companies & the lobe design itself. Crane used 0.004" tappet lift, Comp 0.006", Ultra Dyne [ Bullet ] 0.0045".
Click to expand...
Comp. used at least 4 different lift points for advertised duration..........just for hydraulics.
 
My HE 3038AL Hughes cam has 13.5*@.050.
It specs at 230/237/110, and
276/286/110 advertised, is 61*overlap@ .008 for these AL cams
This is a modest intensity cam:
going from 276 to 230in = 46* on the intake side and
from 237 to 286= 49* on the exhaust.
This cam makes good power in my 367 streeter; and reasonable torque, but sucks gas compared to the next smaller Hughes, that I previously had.

The HE2430AL at 224/230/110 has just 7* overlap at 050, and
270/276/110 that generates 53*overlap @.008 tappet
I really loved this cam and was very sad when it dropped lobes. Mega torque and power at 11.3 Scr, and fabulous fuel-economy with a double-overdrive, geared to 65=1600/ 85=2100.


BTW
with only an overlap number, it is impossible to accurately determine the "size" of the cam; other than 12* is a "good size" or "reasonable size", for a streeter with a "good" or "reasonable" amount of cylinder pressure, with a well-chosen stall and gears. But
if not matched, could just as easily be a gas-sucking lazy pig.
 
Last edited:
At advertised duration by DV

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I have pages & pages of Comp Cams lobe specs. The adv duration for all automotive hyd lobes is at 0.006" tappet lift, flat tappet & roller. The only hyd lobe that was NOT 006 was Harley lobes.
 
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