Cam overlap

[dave ellis]

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".

 

[Newbomb Turk]

Why only 12 degrees? That isn’t much.

 

[4spdragtop]

 

[1MeanA]

I don't think you have enough info. Is there not a part number on the cam?

 

[ch1ll]

You can figure it out if you have the intake and exhaust lobe centerline and the duration of both lobes.

 

[Killer6]

228deg@.050" on 108 LSA would be 12deg overlap@.050"

 

[dave ellis]

I don't think you have enough info. Is there not a part number on the cam?

Hughs cam he0914bl. It's an old cam.

 

[dave ellis]

I believe there is a formula but haven't been able to locate it

 

[1MeanA]

Specs are here . I think there are calculators to figure out duration at 0.006 buts it’s only approximate (google finds them) hughesengines.com/TechArticles/heseriescamprofilesbigblockhydraulic.php

 

[Killer6]

.....
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......
236deg@.050 on a 112LSA is 12deg overlap@.050....... how many more do You want...

 

[Bewy]

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".

 

[Killer6]

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".

Comp. used at least 4 different lift points for advertised duration..........just for hydraulics.

 

[AJ/FormS]

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.

 

[273]

At advertised duration by DV

 

[AJ/FormS]

@273 Nice find!

 

[Bewy]

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.