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One more thing. It's valve spring FORCE, not pressure... Pet peeve of mine.

Take rocker arm mass and multiply by 0.33 and add this to the mass of the valvetrain. Then and 1/2 the weight of the valvespring. This is your total effective mass at the valve for a finger follower valvetrain. Then just use F=ma. It is that simple. Preload is driven by worst case pressure...

Hello, What is a good book on piston port, 2 stroke engines? I'm asking as I am starting to kart race a yamaha kt-100 next year after running nhra stock eliminator for 10 years. My 4-stroke engine knowledge is good, but zero experience with 2-stroke. Thanks, Chris

Another advantage of roller camshaft bearings is the camshaft is better located. Meaning the cam is not "floating" on oil in the bearing. The entire valvetrain will be much stiffer, and a stiff valvetrain is a good valvetrain.

Actually, something else probally screwed up in the valvetrain, eg poor cam design, valvespring surge, lack of valvespring force. Something got wacky and caused excessive lash, the hydraulic lifter is just doing it's job.

Why just hydraulic rollers? The physics are the same reguardless of lifter design.

Pat, Thanks for sharing your experiences. The class I compete in does not allow this, or any, modifications. Why only weak springs? Seems like you'd have the entire lifter valley to play with. Even if the diameter is somewhat small as the pushrod is close to the block, you should get decent...

Has anyone ever tried a rev-kit? What has been your experiences? Good, bad, didn't make a difference? I'm just curious...

enginead, Would a digital volt meter be the same as an analogue to digital converter? Also, what is "HT" interference? Shaun, What can you share about tuning the Q-Jet? Idealy, I think a constant A/F ratio throughout the operating range should be best for best performance. If...

I'm considering putting an O2 sensor in my exhaust system to aid in tuning. However, I have zero experience using O2 sensors and do not know their limitations and tendencies. The current set-up is: 4.3L V-6 Even fire Chevy VP C-10 unleaded racing fuel 4 bbl Q-Jet carburetor 6 into 2 stepped...

John, Sorry for taking so long to get back to you... I'm not real strong in this aspect of cam design, but here goes. Basically, you have to determine what the radius of curvature of the cam needs to be for a particular lift profile vs. roller diameter. I'm not sure how to explain it though...

I should have posted more the first time... I work for a major tier 1 supplier of valves and valve train parts. We do not design camshafts, but we are very knowledgable on their design, materials, dynamics, etc. What specific questions do you have? Chris Hill

John, Specifically, what do you want to know?

The lack of opening and closing ramps on a hydraulic cam (compared to a solid) is probally the reason why. Vizards book on SBC cams and valvetrains discuss this specifically. Reguardless, ANY HYDRAULIC lifter will decrease the natural frequency of the valvetrain, and thus will limit how fast...

What does the variable duration tappets do? Or specifically, how do they work?

Type 1: Direct Acting Cam- cam>bucket>valve Tyep 2: Finger Follower Type - cam>end pivot rocker arm roller>valve Type 3: Center pivot rocker arm - cam>center pivot rocker arm> valve Type 4: Cam>lifter>rocker arm>valve Type 5: Cam>lifter>pushrod>rocker arm>valve Examples Type 1: Porsche...

Does anyone recomend a SAE book or paper that shows how CFD can be used to aid in cylinder head design?