Don Terrill’s Speed-Talk

In a solid cam application with a steel cam using tool steel lifters how much advantage can be gained from a larger cam core and larger lifter dia. For example a sbc with a 55mm cam and .904 lifters

Stiffer cam = less lift loss with stiff valve springs. Others will chime in, too.

X2 what Krooser said.
904 lifters will allow a more aggressive grind on the cam.

Allan.

Give the new HARDKORE CAM SERIES by Mike Jones a go!!

Less twist on the cam, and the biggest factor, which should also be the primary reason, better lobes....Most cam designers these days are recycling old lobe designs on standard cam cores. Going with a bigger core gives them more "room" to make a better lobe design. I'm running a 55mm cam in my stuff, but my head guy wants to go to a 60mm. It will be worth some power, easier on the valve train, and gives more choices in lobe design. Other than the cost of machining, no disadvantage to running a larger cam core. You may, however, run into an oiling issue if the oiling band on your lifters is pushed too far away from the lube hole in the lifter bores. This is corrected by either lifter mods, or using bushings with grooves to allow for proper oiling....I'll be going the bushing route, but I'm also going to a somewhat larger lifter diameter and wheel....also beneficial......

Been there done that on roller cams but this limited dirt track stuff I'm getting into is different. Should have been more specific, was wondering about love design. More specifically the intensity or lift rate.

rcparker wrote: ↑Sun Jun 21, 2020 10:23 am Been there done that on roller cams but this limited dirt track stuff I'm getting into is different. Should have been more specific, was wondering about love design. More specifically the intensity or lift rate.

Unlike a roller cam, a flat tappet profile is not mechanically effected by base circle diameter(unless it gets so small, the nose radius of the lobe gets so small, it creates wear issues.
The Lifter diameter is what limits you. With a flat tappet cam, no matter what the base circle, the radius of the lifter face limits the maximum velocity you can move the lifter.
For an example, a SB Chevy with standard journal size, and an .842" diameter lifter is limited to the same maximum lifter velocity as a SB Chevy with 55mm journal size, and an .842" diameter lifter.

With a flat tappet cam, the only reasons to go to a larger journal, is to have a larger barrel diameter, to reduce flex, and twist, and to have a larger nose radius to reduce wear.

Thanks Mike, so how much advantage is gained going from a .842 to a .874 to a .904. besides the core stiffness is there a point in solid cam design that mandates a larger core or are the design limitations of a solid lifter reached first. Thanks for your input

rcparker wrote: ↑Sun Jun 21, 2020 5:24 pm Thanks Mike, so how much advantage is gained going from a .842 to a .874 to a .904. besides the core stiffness is there a point in solid cam design that mandates a larger core or are the design limitations of a solid lifter reached first. Thanks for your input

Using a .008" safety margin:
The max velocity for a .842" lifter is .0072078"
The max velocity for a .875" lifter is .0074958"
The max velocity for a .904" lifter is .0077489"

The only times you need to go to larger journals, for a bigger bases circle, with flat tappet cams, is when the nose radius gets too small, for the spring pressure you're running. It's not a performance issue, it's a reliability issue.

Mike,
What will the maximum velocity be for a 1" lifter?

Thanks Mike, exactly what I was looking for. If I ever build this I'll be giving you a call

frnkeore wrote: ↑Mon Jun 22, 2020 1:55 pm Mike,
What will the maximum velocity be for a 1" lifter?

Using a .008" safety margin:
The max velocity for a 1.000" lifter is .0085866"

CamKing wrote: ↑Mon Jun 22, 2020 10:36 am

rcparker wrote: ↑Sun Jun 21, 2020 5:24 pm Thanks Mike, so how much advantage is gained going from a .842 to a .874 to a .904. besides the core stiffness is there a point in solid cam design that mandates a larger core or are the design limitations of a solid lifter reached first. Thanks for your input

Using a .008" safety margin:
The max velocity for a .842" lifter is .0072078"
The max velocity for a .875" lifter is .0074958"
The max velocity for a .904" lifter is .0077489"

The only times you need to go to larger journals, for a bigger bases circle, with flat tappet cams, is when the nose radius gets too small, for the spring pressure you're running. It's not a performance issue, it's a reliability issue.

I know that's not what you mean, but it is a performance issue when the cam is whipping around.

Cam core journal size to me is one of those things where going to the largest that can safely fit in a given block is always a win.

hoffman900 wrote: ↑Mon Jun 22, 2020 4:13 pm

CamKing wrote: ↑Mon Jun 22, 2020 10:36 am

rcparker wrote: ↑Sun Jun 21, 2020 5:24 pm Thanks Mike, so how much advantage is gained going from a .842 to a .874 to a .904. besides the core stiffness is there a point in solid cam design that mandates a larger core or are the design limitations of a solid lifter reached first. Thanks for your input

Using a .008" safety margin:
The max velocity for a .842" lifter is .0072078"
The max velocity for a .875" lifter is .0074958"
The max velocity for a .904" lifter is .0077489"

The only times you need to go to larger journals, for a bigger bases circle, with flat tappet cams, is when the nose radius gets too small, for the spring pressure you're running. It's not a performance issue, it's a reliability issue.

I know that's not what you mean, but it is a performance issue when the cam is whipping around.

Cam core journal size to me is one of those things where going to the largest that can safely fit in a given block is always a win.

You missed this part of the OP's question "besides the core stiffness is there a point in solid cam design that mandates a larger core"