View Full Version : rev kit needed? hyd. roller cam with 6000 rpm max


Chuck78
06-04-2005, 11:28:00 AM
I was of the opinion that I did not need a rev plate kit for my hydraulic roller cam (218/230 @ .050" .326"/.340" lobe lift 111.5 lsa), but the guy at the machine shop is trying to sell me one, saying that it's a must, and that it is necessary to keep the lifters in place, and that if one of them ever came out, I would have catastrophic engine failure becuase I would then lose all oil pressure.

A very helpful guy at the counter at Jeg's is telling me that's not necessary for under 6000 rpm, and that's the opinion that I was getting from board members.

Is this correct, or is it still a good idea to have one?

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'71 RS/SS project: full roller 406sbc / 9.76:1 w/ E-Tec Al. heads / 750 Competition AFB / big 4 whl discs, 1-5/16 VSE ft & 1" Rancho adj. rr sway bars / 4 speed 3.23 posi / 81 Z28 & dual snorkel vette Air Induction

Tokyo Torquer3
06-04-2005, 12:59:00 PM
I beleive it will not help you under 6500 rpm with that mild cam. The rev kit helps keep the lifter rollers from flying off the cam lobe at high rpm so they don't get hammered. However, you can still have valve float as low as 5000 to 6000rpms and this is due to poor spring control and the valves bouncing of their seats when they close rapidly due to the more agresive roller cam lobe profile. I have a rev kit and a mild hydraulic roller cam and it didnt help at all, as I still had valve float at 6000rpm. I am no expert but I am working through this issue and have found very few experts even at the cam companies that can give good advice. Telepohone jockeys are useless. On a hydraulic roller, I now beleive the valve spring seat pressure is key to keep the valves from bouncing off their seats, but do not exceed 150 pounds on any hydraulic roller or you will just end up collapsing the lifter. I am going with 140-145 pounds on the seat. Most cam companies do not recommend enough seat pressure, suggesting less than 120 pounds. You could probably sneak by with your set up with a tad less seat pressure than 140-145, but I would not go less than 130 pounds on the seat. I would also try to keep open pressure not less than around 300, but not more than 350 pounds.

Your rocker arm ratio will also be a factor. I don't think you need the rev kit (bitch to install, too) with that small a cam in a 406 since your max RPM will be well below 6000rpm, but pay careful attention to seat pressure. Also, when adjusting the lifter prelaod/ rockers, do not go more than 1/4 turn and definitely not more than 1/2 turn on the preload. It will rpm higher by minimizing the preload.

Again, I am no expert..but I had trouble finding good advice on this issue over the past year and this is what I have learned.

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1973 RS Z28: Littlefield race series 6-71 supercharger on a 355 w/ AFR 195 heads, 12-14 lbs boost, 7.6:1 static compression, CompCams hydraulic roller (276/288 advertised, 224/236 @.050 duration, .510/.527 lift w/ 1.52 rockers on a 113 lobe separation), AFR Hydra-Rev kit, Eagle 4340 Forged Steel crankshaft, ARP studded bottom end, Eagle ESP H-beam rods, TRW forged reverse dome pistons, Comp Pro-Magnum 1.52 roller rockers with 7/16 studs, twin 750 Edelbrock carbs, 1&3/4 inch Hooker Super Comps, 3" dual exhaust with cross over pipe. MSD 6AL ignition & Pro-billet distributor, Tremec TKO-500 5-speed, Moser 12 bolt with Eaton posi, 33 spline axles & 3.42 gears.