Hey guys, years ago I built a 327 with a set of Vortec heads and a retro fit hydraulic roller cam. I could never get the lifters to oil. You can read about this mess here. https://www.jalopyjournal.com/forum...-journal-327-no-oil-pressure-at-idle.1024437/ I am trying to decide what to do with it now. It’s taking up space and the money has already been spent. I am a little skeptical of this retro hyd roller setup. The question I am pondering is am I going to have to get another set of springs if I convert back to a standard flat tappet cam? The ramp profiles on a hyd roller are more aggressive that a flat tappet. The cam profile was a mild roller. Roughly .495” of lift. Howards Cams, Hydraulic Roller Camshaft for Chevrolet SB 305/350, 213/217 @ .050, .485/.495, 112 LS I hate to throw good money after bad, if it’s not required. I think I know the answer, but hoping I don’t have to pull the heads off.
What spring pressure's do you have now and what does the new cam call for? How long has it been sitting with the valve's adjusted? You might want to consider new springs anyway, the springs on the open valve's could have lost pressure from being compressed. You should be able to change the springs without removing the heads. Personally I'd go with the matching springs for the new cam.
Root. I could be wrong but I think you will have to change the springs. It can be done without pulling the heads.
I can’t remember the spring specs. I’ll probably end up changing them. I guess I could try air in the cylinders or the old rope trick. I have a brand new set of roller lifters to see if it starts oiling, but I dunno if I trust the setup now.
It’s been sitting for 5 years now. I’ll have to lube the cylinders just to crank it over. I have a set of 462 castings built up in the rafters. I could swap them out, but I don’t know that I would be gaining anything.
Typically roller cams use higher pressure springs, both initial and fully open. The quicker ramp rates on roller cams need it. Plus there is the roller which isn't in sliding contact with the lobe. If you decide to keep the existing cam with new roller lifters, i would try running the existing springs. If you want to go new flat tappet cam, then get new lower pressure springs to natch what cam needs. Using the roller cam springs could be a good chance of wiping out a lobe and lifter or two.
According to the Howards catalog, the spring for your hydraulic roller has the same spring rate as the spring they list for 3/4 of their hydraulic flat tappet cams too. 411 lb/in rate.....the only difference is the hydraulic roller spring installs .100" taller to accommodate .600" lift. The hydraulic flat spring has only .500" max lift. You can step back to a hydraulic flat tappet no problem, heads can remain just as they are. You don't have to change anything. The hydraulic roller you have isn't radical enough to have needed a higher pressure spring.
Thanks Eric. That’s good to know. I actually found the springs in the non oiling 327 thread. https://www.summitracing.com/parts/hrs-98213
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