Holbay camshaft

[Jay Laifman]

FYI, Rick apparently had the cams measured by Cal Cams. This is the information from Cal Cams with a print out called "The Cam Doctor's Analysis". The numbers are the same as I listed above, but with a higher lift and the additional detaisl.

Holbay (SS) (as measured by Sunbeam Specialties) -

Intake: 27 / 60​

Exhaust: 62 / 25​

Lift .47​

Overlap: 52.1​

Lob Center Sep: 107​

Intake Duration: 268.5 crank deg​

Intake Lobe Area: 26.49​

Exhaust Duration: 266.5​

Exhaust Lobe Area: 26.45​

So what do these numbers suggest to any of you cam gurus?
From my penciling, it looks like I have a shorter gross duration than stock on both intake and exhaust. Hopefully there is more lift and faster ramps that make up for it!
All I know is that my car spins so quickly and freely at the higher rpms - nothing like my stock Alpine ran. But lots of other things can help that too.

 

[Jay Laifman]

FWIW, Rick calls this the "Chrysler Holbay" engine cam.

 

[RootesRacer]

FWIW, Rick calls this the "Chrysler Holbay" engine cam.

Pretty close to the E128 cam.

Doesnt look like an H120 at all.

 

[Jay Laifman]

More info. The sheet that Rick sent me seems to have two readings for the cam - I think. One is the list above - and someone wrote in hand next to it ".020"

Then there is another set of numbers where someone wrote ".050" next to it. Rick thinks this might be what the figures would be with .020 and .050 valve lash settings. Is that possible?

Here are the other numbers next to the .050:

Intake Open: 11.4
Intake Close: 42.6
Duration: 234

Exhaust Open: 45.4
Exhaust Close: 8.5
Duration: 234

Lobe centers and lift are the same.

 

[Jay Laifman]

Pretty close to the E128 cam.

Doesnt look like an H120 at all.

Yeah. The big difference for mine versus the E128 is that my intake opening is delayed a decent amount. I assume that just helps for lower end torque and driveability - which is fine since that's what I'm doing with it.

 

[RootesRacer]

The trouble is that we cant trust any of the opening and closing degrees becuase we dont know at what valve lift (not lash) that they apply.

What we can trust is the lobe center info which we can calculate regardless of the degrees @ lift figures and the valve lift figures.

The 107 degrees lobe centers matches closer to the SV figures than the 103 degree lobe centers the H120 is supposed to have. The .470 lift is just about what the E128/tornado cam was advertised as having.

There does apeare to be some advance to the cam you have the data on which the E128 cam was more or less straight up.

This adds to confusion, but the lobe centers, net valve lift and apparent duration matches closer to the E128 (275 advertised) than the H120.

 

[Jay Laifman]

Ahh. Well maybe I should have provided those from the print out!

Intake:
Max Cam Lift: .31374
Net Valve Lift: .47061

Exhaust:
Max Cam Lift: .31394
Net Valve Lift: .47091

And I had the Lobe centers off:
Intake: 105
Exhaust: 109

The 107 number was labeled as "Lobe Center SEP"
There is also "Valve Overlap" 52.1 Intake and Exhaust

 

[RootesRacer]

Having a lobe center for intake and exhaust makes no sense since lobe centers are the angle between the exhaust lobe nose and the intakes lobe nose.

http://www.claysmithcams.com/lobe-center/

Not sure what those numbers are...

By the numbers, looks like 107 degree lobe centers with 2 degrees advance.

 

[Jay Laifman]

Jay,

"Alpine Marque", issue #7, page 30.

couldn't get the link to copy and work - check header at top of page "SAOCA Info" > "Alpine Marque"

HTH

That's the one. Here's the link: http://www.sunbeamalpine.org/alpine_marque/issue_7.pdf