Cam Lobe / Lifter Bore Offset

General engine tech -- Drag Racing to Circle Track

Moderator: Team

Post Reply
Greenlight
Pro
Pro
Posts: 415
Joined: Wed Feb 16, 2005 10:37 pm
Location:

Cam Lobe / Lifter Bore Offset

Post by Greenlight »

On a flat tappet tapered lobe, with a crowned lifter, what is the typical lobe to lifter bore offset? If no offset is used and the rotation is only caused by the combination of taper/crown, approximately how far over from center does the lifter actually contact the lobe?

Does the typical amount of taper, offset, lifter crown radius differ for an all out race cam setup vs. OEM (100,000 mile ???) setup?

Is there a preferred lifter crown radius and taper that should be used with high valve spring loads or is it a one size fits all kind of thing?


Thanks in advance for any assistance.
Project Greenlight
User avatar
CamKing
Guru
Guru
Posts: 10709
Joined: Wed Aug 08, 2007 4:05 pm
Location: Denver, NC
Contact:

Re: Cam Lobe / Lifter Bore Offset

Post by CamKing »

Lifter offset, .015"-.020" to the rear on a small block chevy.
Mike Jones
Jones Cam Designs

Denver, NC
jonescams@bellsouth.net
http://www.jonescams.com
Jones Cam Designs' HotPass Vendors Forum: viewforum.php?f=44
(704)489-2449
PackardV8
Guru
Guru
Posts: 7619
Joined: Sun Jul 30, 2006 2:03 pm
Location: Spokane, WA

Re: Cam Lobe / Lifter Bore Offset

Post by PackardV8 »

The Packard V8 was designed with a cam lobe taper of 6 min. positioned .0625” back of lifter center.
Is there a preferred lifter crown radius and taper that should be used with high valve spring loads or is it a one size fits all kind of thing?
And no, back in the day, lifter face spherical radius was not a one-size-fits-all. We have a tappet grinder and there is a manual with a chart showing which setting, from #1 to #8, should be used for which make and model of lifter. The Packard V8 uses a spherical radius of 30" and this equates to #8. Other engines have a spherical radius of 100", which is a #2 setting on the tappet grinder. This produces a much "flatter" tappet.

FWIW, we've observed most of the replacement tappets sold today for older engines no longer come with the more crowned radius. The manufacturers won't answer questions as to whether they're just too lazy to adjust their machinery or if they've found benefits to larger radius/less crowned lifters.
Jack Vines
Studebaker-Packard V8 Limited
Obsolete Engineering
wyrmrider
Guru
Guru
Posts: 6941
Joined: Thu Jan 10, 2013 10:52 pm
Location:

Re: Cam Lobe / Lifter Bore Offset

Post by wyrmrider »

REmember when the Chrysler 6-Pack went to a flatter lobe and less crown on the lifter (for durability during the warranty period)
Id make sure the camgrinder matches the taper to the lifter or reface your lifters to match the lobes
no one ran the flatter lifters on a stock Magnum cam- they were to expensive- and did not work well and NLA for decades now
running the more crowned lifter on the flatter taper cam worked but had a higher unit pressure than even the higher crowned lifter on the normal Magnum taper cam
I was service manager at a Chrysler dealer and the cams were not the problem
Customers were just running their Cudas and Road Runners a lot harder than the factory planned for
and then there were those that bought the high hp motor to tow their trailers
Greenlight
Pro
Pro
Posts: 415
Joined: Wed Feb 16, 2005 10:37 pm
Location:

Re: Cam Lobe / Lifter Bore Offset

Post by Greenlight »

CamKing wrote:Lifter offset, .015"-.020" to the rear on a small block chevy.
PERFECT !!!!! Thanks.
Project Greenlight
Racerrick
Expert
Expert
Posts: 697
Joined: Sat Sep 24, 2005 10:52 am
Location:

Re: Cam Lobe / Lifter Bore Offset

Post by Racerrick »

To measure lobe taper you put the cam between centers in a lathe then set up a dial indicator on lathe carriage so the point of the indicator is on the lobe at base circle then move the carriage from lobe edge to lobe edge. what you will find is, stock cams are .001 or so and race cam can be high as .003. the higher the taper the faster the tappet spins. some engine have all the lobe taper the same way like GM and other have them alternating like a ford
Post Reply