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Max RPM Hydraulics?


jlozinsk

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Hi,

 

I am going to completely refurbish my hydraulic lifters (new tops balls etc) then send them to Rhoades Lifters so they blead down. I plan the cam to turn 6,500 RPM with 15 lbs boost on a blower but I suspect I could up the power band if I uped the revs to 7,000 and max power to 6,800 RPM. Currently my cam will peak at 345Hp at 6,300 RPM. Has anyone run a hydraulic set up to 7,000 RPM?

 

Thank you

 

John

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Hey John,

 

I would not try to rebuild the lifters, just gather a bunch of used ones in case you need to swap one or two out. I've got some spare used ones if you need a couple. I've heard that when you try and rebuild them, they are never the same. You can also convert your P90A to solid too.

 

My L28 turbo pulls strong right to 6000 RPM with hydraulic lifters. Stock turbo cam.

 

Another thing to keep in mind is that if you purchase an aftermarket cam for you hydraulic head, it needs to have the correct profile for hydraulic lifters. All aftermarket cams that I have seen are for solid lifter heads only.

 

I'm in NH, we should hook up.

 

 

Pete

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Is any modification required to run the hydraulic pivots to 7000? My 83 ZXT seemed to tolerate 6500 without much ado. Is the extra 500 rpms that critical? Is it a hydraulic regrind or a mechanical regrind---as from my understanding the ramps on the two different cams are quite different.

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I too am quite interested in just how many RPM can hydraulic lifters/adjusters go before they “pump up” or hit whatever limit/issue hydraulic lash adjusters run into? I haven’t really dug into this topic myself, though I am curious if this is a universal issue/limit or dependant on lifter design/manufacturer or is it a myth masking the issue of possibly weak valve springs? We read about it all the time regarding domestic V-8,s. Some sources will claim as low as 6000, others claim as much as 7500, others claim it depends on the lifter and manufacturing tolerances in the clearances, others claim it is related to how much valve spring pressure, others claim how much oil pressure feeding the lifter, others say it depends on where in the “adjustment range” the lifters are set to.. etc etc etc…

 

Not sure of the relevance regarding the L-6 hydraulic lash adjusters, but I’ll share my later model Nissan hydraulic experiences. My ’96 Infiniti Q-45, VH45DE, has hydraulics lash adjusters and the factory rev limiter limits RPM to 7100 RPM. It ran great, never missed a beat all the way to the rev limiter. My ’93 Z-32 with VG30DE, hydraulic lash adjusters, recently replaced the factory ECU with a WOLF 3-D V-500, programmed the new rev limit to 7300 soft cut, 7400 hard cut, runs great all the way up, the WOLF rev limiter is MUCH smoother and virtually seamless as compared to the OE rev limiter. No noticeable hydraulic lash adjusters pumping up or valve float.

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with the same performance.

 

Not sure I'd say that, but it all depends on your priorities, I suppose. After having tinkered with quite a few vastly different cars, I'd prefer solid. Especially on something as easy as the L-series to adjust. But then, silent is very low on my list of priorities.

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Is any modification required to run the hydraulic pivots to 7000? My 83 ZXT seemed to tolerate 6500 without much ado. Is the extra 500 rpms that critical? Is it a hydraulic regrind or a mechanical regrind---as from my understanding the ramps on the two different cams are quite different.

Crower is giving me a billet cam and they seem to think 7,000 is not practical.

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More Boost achieves the same horsepower without trick parts and one-off components...

 

Not as snazzy when it comes to benchracing, but from a practical standpoint 'horsepower is horsepower' and from an engineering standpoint I would think the lower the rpms it's achieved at, the better as reversal loads go up as speeds go up...

 

Is there a particular reason you need to turn 7000 rpms (i.e., Bonneville Top Speed Trials, Trap Speed due to gearing, etc) or what? If it's simply horsepower you are after, turning up the boost will achieve the same results far cheaper.

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