# Hydraulic camshaft max rpm?



## beqa16v (Oct 10, 2010)

Hi guys. 
I have posted another thread on my project but the moderator suggested that I could start a new thread on this particular question in technical forums. 
So, I'm interested in capabilities of hydraulic camshafts. What is a maximum cam size you can run on hydraulics and how high can you rev it without converting to solid lifters? I read on 288 you need to machine some parts to keep it clear but other than that, how high can I rev with hydraulic? Also how much crank hp can be achieved this way? 

my project thread is here: http://forums.vwvortex.com/showthread.php?5050042-Recommendations-for-1.6-race-engine


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## ABA Scirocco (May 30, 2001)

The best I've seen with a hydraulic lifter 8v was a 2.0L engine that made about 185 hp at the crank. That car was set up so that the engine would turn about 8000 -8200 rpm at the end the straightaways.


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## beqa16v (Oct 10, 2010)

thanks, thats more then enough for my goals


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## chrisbmx68 (Aug 14, 2003)

i second aba scirocco the max I would ever take them is around 8000 don't worry though a tt 288 hydro wont make any power up that high anyway esp on a stock head


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## beqa16v (Oct 10, 2010)

chrisbmx68 said:


> i second aba scirocco the max I would ever take them is around 8000 don't worry though a tt 288 hydro wont make any power up that high anyway esp on a stock head


I do not have high expectations with the stock head but what about P&P German crossflow?
And if not TT, then which hydro cam will make power at 8K?


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## chrisbmx68 (Aug 14, 2003)

none, thats pretty much as big as you can go. 

Crespo sells lifters that take stock style rabbit/jh shim pucks and are longer to fit hydro valves. Then you could run any off the shelf solid lifter cam in your aba head. (limited to .475 lift)


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## ABA Scirocco (May 30, 2001)

The engine with a hydraulic head that I saw dynoed at 185 hp, had Crane biggest hydraulic lifter cam, unfortunately that cam is NLA but TT's biggest hydro cam, a 298, would likely be comparable. A properly set up motor with well ported cross flow head and something like TT's biggest hydro cam will make it's peak power somewhere around 7200 rpm and although the power will have dropped off somewhat by 8K it will still be pulling pretty strong. 

Personally, I wouldn't recommend those Crespo lifters for a high rpm racing engine for a few reasons, first, because they have the shims on top, they effectively reduce the diameter of the lifter by a couple millimeters and this restricts the size and duration of the cams you can use to the point were you wouldn't be any better off than you would be with a big hydro racing cam. Second, although I've never witnessed it myself, it's not unheard of for a shim to get dislodged at high rpm and would cause considerable damage. And finally, those Crespo lifters are HEAVY much heavier than a normal stock solid lifter or a stock hydraulic lifter.


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## chrisbmx68 (Aug 14, 2003)

good points all around I wasnt aware tt had a 298 hydro cam!

ive heard the shims fly out around .500 lift with an aggressive ramp. I just suggested that as a easy solution and selection of a lot more cams.


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## ABA Scirocco (May 30, 2001)

chrisbmx68 said:


> good points all around I wasnt aware tt had a 298 hydro cam!
> 
> ive heard the shims fly out around .500 lift with an aggressive ramp. I just suggested that as a easy solution and selection of a lot more cams.


The TT 298 is a fairly new addition to their line up.

The main problem with top side shims is the size, the shims are something like 33mm in diameter, the lifter itself is 35mm, when you install a big cam, you need to make 100% certain the lobe of the cam doesn't contact the edge of the shim or it will result it greatly accelerated cam wear, dislodged shims or even cam breakage. With a stock base circle cam, the biggest you can go is somewhere around .465" lifter, the exact number varies considerably depending on the profile of tha cam.


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## chrisbmx68 (Aug 14, 2003)

makes sense, pretty much the reason I went to shim unders on the head I just had rebuilt. I have a spare set with a 4mm foot if you know anyone needing such a thing


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## Str8pipingti (Oct 10, 2010)

you could always got solid lifter and get autotechs 306* cam for an even bigger lift


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## ABA Scirocco (May 30, 2001)

Of the things you look for in a cam, lift is one of the less important ones because the ports on an 8v head, even a well ported one, don't flow much (if any) more at .450" than they do at .500". Things like cam profile and overlap have MUCH more impact on the performance of a cam than lift.


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