100# SEAT PRESSURE ON ROLLER CAM

[perfconn]

I am curious as to how the cup engine builders are running 100# of seat pressure on a roller cam? I know part of the technology is using 7mm valve stems,light retainers,steel rockers,1/2" pushrods ,Jesel keyway lifters & high rate springs but there is bound to be a difference in the cam lobe profiles.I have heard of the controlled valve float principle but the setting of the valve back on the seat is what really mystifies me.

[David Redszus]

I am curious as to how the cup engine builders are running 100# of seat pressure on a roller cam? I know part of the technology is using 7mm valve stems,light retainers,steel rockers,1/2" pushrods ,Jesel keyway lifters & high rate springs but there is bound to be a difference in the cam lobe profiles.I have heard of the controlled valve float principle but the setting of the valve back on the seat is what really mystifies me.

A lower seat force can be used if all valve train components are very light weight and the cam shaft acceleration profile is mild.

[user-612937456]

Exactly and I'd say the super top Secret ramp profile is key plus the featherweight valvetrain Dave hit the nail on the head

[DaveMcLain]

What gives better high speed valvetrain control? A spring with a lower rate that is shimmed to give a high seat load or a spring with a higher rate that is shimmed less but has a higher resonant frequency and thus more resistant to spring surge in the operating range of the engine. Spring surge can cause a spring to have zero seat load at certain engine speeds so I'd put my money on a higher rate spring irregardless of the seat load.

[CamKing]

Remember, 100# with a 2.3:1 rocker ratio is 230# at the lifter.

[allencr267]

So called 'rev-kit', spring/s between the lifter & block besides the spring/s between the retainer & head?
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Also, smaller. it's spring isn't working at a mechanical disadvantage against the valve train's biggest mass.

[CamKing]

So called 'rev-kit', spring/s between the lifter & block besides the spring/s between the retainer & head?
////
Also, smaller. it's spring isn't working at a mechanical disadvantage against the valve train's biggest mass.

no rev-kit

[perfconn]

Rev kits went out in the 80's Most of the lifters made today won't even take a rev kit..9500 with no rev kit equals not needing a rev kit.

[cgarb]

2.3-1...wow that's a game changer. The lobe they are running must be pretty small then as far as lobe lift. I assume that is what allows them to do this, plus the lightweight valvetrain. That had been my point when talking about roller cams with some local people I race with. One builder goes by the 100lbs open per .100" of lift. That sort of makes sense to me, and I see his point but what makes a .600" lift roller different than a .600" flat tappet? The flat tappet spring is able to shut the same valve at 7000rpm why wouldn't it be able to shut a roller tappet?

[carmakerevive]

Larger wheel diameter on the lifters too.

[GARY C]

The first solid roller I ran was a used .550 lift with 2 different brands of lifters and I ran this spring...
"Upside down" Conical Valve Spring
Rate: 362 lbs
Inner Diameter: 1.070'' Top, .866'' Bottom
Outer Diameter: 1.454'' Top, 1.250'' Bottom
Seat Load: 100 lbs at 1.750''
Open Load: 281 lbs at 1.250''
Coil Bind Height: 1.135''

It would turn 7000 with out missing a beat, I guess it worked because I didn't know any better.

[CamKing]

The first solid roller I ran was a used .550 lift with 2 different brands of lifters and I ran this spring...
"Upside down" Conical Valve Spring
Rate: 362 lbs
Inner Diameter: 1.070'' Top, .866'' Bottom
Outer Diameter: 1.454'' Top, 1.250'' Bottom
Seat Load: 100 lbs at 1.750''
Open Load: 281 lbs at 1.250''
Coil Bind Height: 1.135''

It would turn 7000 with out missing a beat, I guess it worked because I didn't know any better.

It worked because it was a mild .550" lift cam. If the lift curve is the same, the valve doesn't know if it's a roller cam, or a hydr flat tappet.

[GARY C]

The first solid roller I ran was a used .550 lift with 2 different brands of lifters and I ran this spring...
"Upside down" Conical Valve Spring
Rate: 362 lbs
Inner Diameter: 1.070'' Top, .866'' Bottom
Outer Diameter: 1.454'' Top, 1.250'' Bottom
Seat Load: 100 lbs at 1.750''
Open Load: 281 lbs at 1.250''
Coil Bind Height: 1.135''

It would turn 7000 with out missing a beat, I guess it worked because I didn't know any better.

It worked because it was a mild .550" lift cam. If the lift curve is the same, the valve doesn't know if it's a roller cam, or a hydr flat tappet.

Yeah it was one of Comp's old "Street Solid Roller" I think it was something stupid like 255/555 if memory is correct...Long, Slow and not a street cam.

[steve cowan]

camking,
i am going to guess,
low seat pressure,high spring rate to control the valve at high rpm,and valve loft but they probably like the valve lofting if it stays in control
low seat pressure to save the valve face and seat from getting beat to hell because of the 55 deg plus seats angle for 500 mile race
again i am usually wrong most of the time but happy to learn

steve c

[pamotorman]

how many remember the 1/4" X 1/4" steel bar that went into the lifter oil galley and fit thru a slot in the roller lifter to keep it from rotating ?? I remember using this in the 60s but I don't remember the brand