evil 944t

I know a 7200rpm motor with aftermarket springs thats running fine but, 8 - 8.5k,
WOW thats high!

APKhaos

I thought mine was running fine too. Blew a head gasket last race of the season, which was the only reason the head came off. Found seven broken springs!!! No valve to piston contact, so guess I dodged several bullets.

Guess the point is that broken springs might not that obvious unless they cause serious collateral damage.

m42racer

Sorry about that. It was after a long day travelling. The Pauter rod is not a true "A" beam Rod. Its more like a double inverted "T". The steel one I'm talking about. I have never seen their Titanium Rods.

m42racer

Not to change the subject, but to follow on from,

" Not sure even after-market springs will make this valve train safe much north of 7000"

The stock valve train like many stock Valve Trains are not designed for high RPM's. The manufacturer designs only what is required to meet the performance levels they are trying to achieve. Most stock Cam designs are so poor, as they induce huge amounts of "shake" into the Valve Train, especially the Springs. Stock springs are usually very low grade in design and steel. Most have a low natural frequency so with higher RPM's they reach their natural Frequency limit and break. To run the higher engine speeds, bigger dia Valves and more manifold pressures, (heat) the spring forces have to be increased. Up goes the hertz values, the wire stress, etc, and sooner than later they will fail.

There are some very good replacement springs for these engines out there. The Top Retainer usually needs to be changed to use these Springs, but changing over to these Retainers helps to. Most are Titanium which helps with the total mass of the Valve Train working against the Spring.

I don't think 8000 is very high today. Maybe with these older engines with the stock parts it is. But with tyhe new parts coming vailable by some, running these speeds will be possible.There's no point in running up there if the Head won't flow up there. To run those speeds many other parts would probably need to be changed as well. Not sure if the Stock Crank would survive to much of those RPM's without a good dampner fitted.

RogueM3

Titanium is a bad idea in a street driven valvetrain just due to its inability to last. Titanium springs and retainers need to be replaced every 20k miles or so...well worth it on a race motor..but not on a street car.

Lots of NA cars run up to 7500 or so (Euro-spec e36 m3....E46 m3)...It really isnt so high in more "modern" motors. My 96 3.2l runs up to 7200 with my software (granted I stop making power at 6950 or so)

-Richard

Porsche-O-Phile

I doubt I'd rev the engine all that high, to be honest. I might raise the rev. limit 250 or something, but I doubt I'd push it much higher than that. It'll have plenty of power (a 2.8L with 18 psi of boost? I think I'll be okay. . .) and the Callaway turbo spools pretty darned quickly so I'm not that concerned with being able to tach. higher. It won't ultimately gain me much. It does sound like the Carrillos are the better choice though given the geometry. Thanks for the input.

m42racer

"Titanium is a bad idea in a street driven valvetrain just due to its inability to last."

Poorly made Titanium parts maybe, but not so if they are well made and designed. Most well made Retainers are coated to stop the chaffing. Also if the Retainer is made so that it snaps onto the spring, everything will work fine. Problem is most Retainers are never made properly.
I know of many steel Retainers from engines I have had that are known to crack to fail. Also, the use of Titanium Valve keepers on Steel valves is highly regarded as been better than steel on steel for wear.

I doubt it if anyone would consider the use of Titanuim Valve Springs for the street. The price would put most off. Again, a well made Titanium Spring would be better than a poorly made steel Spring.