Solid roller lifters?
12-20-2016, 07:28 PM
#133
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Bigger wheel lifters pick up on your .020 .050 and all your numbers quicker and its a good to get with your cam grinder so they can grind the cam according to your wheel size being used.
Some of my engines I build their are classes where certain cams must be used and going from a .750 to .850 wheel makes a difference because it pick up on your numbers quicker.
Last edited by CNC BLOCKS; 12-20-2016 at 07:34 PM.
12-20-2016, 07:40 PM
#134
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Any time you can reduce the pressure angle of the lifter is a big plus, More lift equals reduced base circle, Smaller base circle increases pressure angle which does not make for happy lifters.
Bigger wheel lifters pick up on your .020 .050 and all your numbers quicker and its a good to get with your cam grinder so they can grind the cam according to your wheel size being used.
Some of my engines I build their are classes where certain cams must be used and going from a .750 to .850 wheel makes a difference because it pick up on your numbers quicker.
Bigger wheel lifters pick up on your .020 .050 and all your numbers quicker and its a good to get with your cam grinder so they can grind the cam according to your wheel size being used.
Some of my engines I build their are classes where certain cams must be used and going from a .750 to .850 wheel makes a difference because it pick up on your numbers quicker.
And one more question do you put .937 lifters in a dart BBC with out doing a bushing for the oiling? On a 55mm cam.
Last edited by 14 apache; 12-20-2016 at 08:06 PM.
12-20-2016, 08:07 PM
#135
[QUOTE=CNC BLOCKS;4511360]Going to bigger cam cores and bigger rollers effects pressure angle in a good way. Less pressure angle happier lifters!!
http://performancetechnician.com/pdf...a-Lifter-2.pdf
Once you’ve made the move to roller
lifters, your choices and options get better.
Obviously, friction is reduced because you’re
rolling over the lobe instead of dragging over
it. Where the flat lifter is velocity-limited, the
roller lifter is acceleration-limited. You can
only achieve so much rate of lift before the
pressure imposed by the wheel on the lobe
initiates contact failures. The pressure angle
is the angle formed as the roller impacts the
lobe. The advantage of a roller is that you can
shorten duration while maintaining high lift, but
in doing so the wheel almost gets driven into
the side of the lobe on the opening ramp. By
necessity, the first point of contact has to be
something above the centerline of the cam
core, otherwise the lobe just tries to knock
the wheel off of the lifter. If you look at some
of the photos, you can see where the roller
wheel marks the lobe. There is considerable
side thrust generated and this will be seen
as increased wear in the lifter bushing, often
in an hourglass pattern, wide at the top and
bottom and at or near specification in the
center of the bore. Using a larger diameter
cam core helps reduce pressure angle, as
does using a roller lifter with a larger wheel.
If you use a larger wheel, remember that
while the lift will be unchanged, a larger
wheel will increase the effective duration
of the cam, opening the valve earlier and
closing it later. You will need to account for
this when you talk to your cam grinder.
should full force read this? seams like the answer to his 193 page cam lobe question........ thoughts anyone?
http://performancetechnician.com/pdf...a-Lifter-2.pdf
Once you’ve made the move to roller
lifters, your choices and options get better.
Obviously, friction is reduced because you’re
rolling over the lobe instead of dragging over
it. Where the flat lifter is velocity-limited, the
roller lifter is acceleration-limited. You can
only achieve so much rate of lift before the
pressure imposed by the wheel on the lobe
initiates contact failures. The pressure angle
is the angle formed as the roller impacts the
lobe. The advantage of a roller is that you can
shorten duration while maintaining high lift, but
in doing so the wheel almost gets driven into
the side of the lobe on the opening ramp. By
necessity, the first point of contact has to be
something above the centerline of the cam
core, otherwise the lobe just tries to knock
the wheel off of the lifter. If you look at some
of the photos, you can see where the roller
wheel marks the lobe. There is considerable
side thrust generated and this will be seen
as increased wear in the lifter bushing, often
in an hourglass pattern, wide at the top and
bottom and at or near specification in the
center of the bore. Using a larger diameter
cam core helps reduce pressure angle, as
does using a roller lifter with a larger wheel.
If you use a larger wheel, remember that
while the lift will be unchanged, a larger
wheel will increase the effective duration
of the cam, opening the valve earlier and
closing it later. You will need to account for
this when you talk to your cam grinder.
should full force read this? seams like the answer to his 193 page cam lobe question........ thoughts anyone?
Gold Member
12-21-2016, 07:37 AM
#139
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I machine a lot of blocks for other builders and engines shop can only go by their feed back.
I have a customer in Hawaii that has two Dart SHP Pro blocks with a 55MM cams and .904 lifters and no bushings one engine is 3 years old.
The only problem with bushings there is no way to clean the oil galleys out once installed.
Dart BB's have tall lifter bores and so far no problems, Never done a 55MM and .937lifter yet.
World blocks have to short of lifter bores to go to a 55MM cams some blocks the lifter bores are counter bored so much they are only 1.250 in length.
The 55MM cam and .904 lifter in BBC seems pretty common now.
I had some custom cam bearings made for the 55MM cam with one hole and a groove to control bleed off. All the 55MM cam bearings I have seen have 3 oil holes for that size housing bore it creates a lot of windage problems. I use these in SBC, BBC and SBF.
Here is a link on those cam bearings
http://www.yellowbullet.com/forum/sh...d.php?t=999434
I rarely see blocks to machine roller cam bearings any more seems to be a thing of the past. More HP with babbit bearings and less harmonics through the valve train.
12-21-2016, 03:47 PM
#140
Registered
Out shear curiosity, what happens when you reduce cam size and increase ratio on rocker? Whats the tradeoff? More spring or less .idk. Are there gains to be made or just moving issues elsewhere?
