solid roller to hydraulic roller conversion.

[Big_G]

Grumpy and any others: chime in. Hypothetical discussion: In an effort to increase reliability in in relation to the supposed short lifespan of solid roller lifters, I am contemplating going to a hydraulic roller setup. The cheap guy in me asks can I use hydraulic rollers on my existing solid roller (billet) cam? Comp. Cams 244/248/114* lsa/.6** lift. If so, let's discuss the power/performance changes coming from such a change. My current seat pressure is 210#. I know this is too much for a hyd. cam. My rev' limit is 6,300 rpm's, so that should be in reach of good hydraulic lifters. I need high seat pressures, as I run 20 lbs. of boost. Kick it around.

 

[Indycars]

Like you said, 210 lbs of seat pressure is too much for a hydraulic. The 20 lbs of boost would only apply to the intake valve, so you will still have the full 210 lbs on the exhaust valve. Also I thought the solid lifter camshaft has take-up ramps where the hydraulic does not. This ramp eases the lifter up to remove the clearances, before it gets into the higher accelerations. With the hydraulic lifter, the valve will be lifted off the seat for the 20 or so degrees before it was designed for.

Are your solids rollers worn out now? How many miles a year to you drive the car?

Funny you brought this up, I was told my 61 Vette (35 years ago) had the 375 hp solid lifter factory camshaft with hydraulic lifters on it. I always wondered if that could possibly be correct. I never had the engine apart, so I was not able to verify.

 

[Big_G]

Like you said, 210 lbs of seat pressure is too much for a hydraulic. The 20 lbs of boost would only apply to the intake valve, so you will still have the full 210 lbs on the exhaust valve. Also I thought the solid lifter camshaft has take-up ramps where the hydraulic does not. This ramp eases the lifter up to remove the clearances, before it gets into the higher accelerations. With the hydraulic lifter, the valve will be lifted off the seat for the 20 or so degrees before it was designed for.

Are your solids rollers worn out now? How many miles a year to you drive the car?

Funny you brought this up, I was told my 61 Vette (35 years ago) had the 375 hp solid lifter factory camshaft with hydraulic lifters on it. I always wondered if that could possibly be correct. I never had the engine apart, so I was not able to verify.

I only drive it maybe 2000 miles a year, but would like to make that much more. The cam and lifters have about 2,000 miles on them. Maybe I'm being overly cautious.

 

[grumpyvette]

roller cam lobe profiles differ a great deal, the only reasonable course of action is to call and discuss what your attempting to do with the cam and lifter manufacturer, and get their input here.
yes what your planing on doing has been done in the past with various degrees of success,yes youll most likely need a different set of valve springs , but there are other potential problems. swapping to hydraulic rollers on a solid roller cam and Using hydraulic roller lifters on a solid roller cam can be done but it's not usually a good idea from a performance perspective, simply because Solid roller cams usually have very slow lash take-up ramps, which means youll loose effective low rpm and lift & duration and hydraulic roller lifters seldom perform well above 6400rpm without a rev kit and even then they don,t remain stable much over about 6700rpm. so in effect your screwing up both ends of the potential power curve and/or requiring expensive parts for lower performance.
in most cases, it would most likely be easier to swap to a slightly milder solid roller cam, and lower load rate springs, avoiding much of the problems and increase the lifter and valve train oil flow rates . keep in mind its the higher rpms, increased inertial loads and much higher spring load rates that tend to break and wear parts, if you used lower spring load rates and a cam designed for about 6500rpm max rpm that will work with the lower spring load rates and installed the lower load rate springs you effectively lower the potential shock and inertial loads to those similar to the hydraulic roller cams, and if you used a rev limited ignition,, you could effectively increase your cam/lifters expected life span, increasing the oil flow and reducing the loads is bound to increase the component life span.

LIFTERS WITH EXTRA OIL FEED GROOVES CERTAINLY CAN,T HURT DURABILITY
read this link
http://www.hotrod.com/techfaq/hrdp_0510 ... ewall.html
QUOTE
Some classes restrict competitors to hydraulic lifters. Cheaters have been known to run hydraulic lifters on a solid profile. Because they have no quiet lash ramps, solids make for better race profiles. If you take hydraulic lifters and put them on a solid profile, they generally run better than they would on a roughly equivalent hydraulic profile, generating more area under the curve. Hydraulic cams in general are quicker in low-lift, low-rpm, high-endurance applications. Race motors don't care about vacuum and throttle response; they care about area and rpm. Putting hydraulic lifters on a solid grind raises the rpm points at which peak power and torque occur compared to using solid lifters on the same solid cam. However, the actual power and torque peak numbers at the higher rpm points will be lower using hydraulic lifters. That's because the hydraulic lifters installed on the solid cam are slower off the seat, even though they develop more overall duration. Effectively, the hydraulic lifters installed on a solid grind act like a bigger (but slower) cam with very little increase in flow capacity (no more air, but more time to breathe). In terms of numbers, this means a 249-degree-duration (at 0.050-lift) feels like a 255-degree cam.

To successfully run hydraulic-roller lifters on a solid-roller profile generally requires that the solid cam be a tight-lash (under 0.020-inch hot) profile in the first place, with less than 30 degrees difference between the 0.020- and 0.050-inch duration specs.

Duration Vs. Lash

This shows the change in effective duration at the valve from different valve-lash settings on a Comp Cams Xtreme Energy No. 3315 lobe profile. It assumes1.5:1 rocker arms.

Valve Duration at Lash
Lift 0.004" 0.008" 0.012"
0.006" 279.7 273.6 268.6
0.020" 262.5 258.9 255.6
0.050" 240.9 238.6 236.5
0.200" 183.2 181.9 180.6"


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