Subject: Re: Make a 350 out of a 400??? by anesthes on 2009/7/13 23:17:24
Quote:
rklessdriver wrote:
Joe I have used this valve adjustment on hyd rollers a few times in the past - but it really only mask the problem.
With all the work I've put into mine in the past 2yrs (almost), I'm begining to dislike hyd rollers for serious hi-performance engines more and more everyday. Once you get to a certian point it is knives edge balancing act of valve spring, lobe rate and external stability. You get one bit out of kilter in any one of them and the whole shebang goes to hell....
I like mech rollers. If you have good oil supply at the lifter wheel and valve springs a mech roller will live a very long time. A tight lash lobe profile will go a long way to keeping the valve adjustment in check - which is the only other big killer of mech roller parts I have seen. With the HIPPO (MOREL and CROWER) lifters and spring oiler V/C or shaft mount rockers we have now I think one could make a mech roller live forever in a street car.
I'll tell you what... If that fricken hyd roller in my 92 eats one more set of valve springs, I'm going to switch my car over to a T/L mech roller and find out. Will
I've had a lot of issues over the years as well, but I considered it related to boost. I've had springs break, valve float on one pass, but not on another at the same RPM. I've gone with bigger springs to handle the floating, to then have hydraulic roller lifters fail (comp cams).
I've also had issues with the stupid polylocks on the roller rockers losen up, which has nothing to do with hydraulic roller cams but another thing that has driven me nuts over the years.
I like the idea of solid flat tappet, with the exception of break in. It takes a lot of confidence to get crank, broom, and run for 20 minutes especially when your putting something together that has been sitting for years and using mostly new parts. You have to eyeball timing as close as possible, have a parter hold the idle while you get the timing spot on (or you'll burn an exhaust guide/valve), ensure the carb has fuel, ensure no trapped air in the system is going to cause it to overheat, etc.
And if your running EFI, hah, forget it. It's a 50/50 if it will start and idle, sputter and die, etc.
On new hyd motors, I'd go through about 20 starts before I had the base calibration good enough to idle for a while. Good luck doing that crap on a flat tappet cam.
But then, there is the fears of the solid roller lifters exploding. I understand a solid roller cam doesn't need a high idle break in, but any issues with oiling and WHAM! a lifter might break, tanking a $4,000 short block.
Though you would think that a motor with a M55HV pump, that gets like 80+ psi at idle would be fine.. I guess it's not just about the pressure ?
I'm torn... But either way, I think it's going to have to be on a small base circle.
