PT

Hi,
I'm rebuilding the engine and am debating on what valve springs to use.
My plan is to go with titanium retainers but am deciding on stock vs stiffer springs.
My understanding is that stiffer spring will both rob HP and put more load on the cam (hence wear).

So, does anyone know what safe RPM can the stock valve springs sustain?
The car is mainly used on track and I can see me revving regularly to 6700.

Thanks...

Sameer

Aese and I think EBS from Andial.

125shifter

I had EBS install their heavier springs in my heads. I'm not sure what brand they are but they said they were good for 7000. I didn't use Ti retainers because I seen wear on some and I didn't see the need for reving past 7000. I was more worried about floating a valve than loosing some hp or cam wear, I hope it's the right choice.

JoeMag

I have stock springs on my car and redline is at 6800 and i go there a lot. No issues in last 3 years except when i over reved end last season to 7k+ and broke a rocker.

I understand porsche used the 930 springs on the 962 engines also.

Sameer

I hear these ti retainers and race valve spings also do help lighten up the drivetrain/crank. Can you guys explain?

38D

The purpose of a Ti retainer is to lighten up the valve train. The lighter the valve + retainer, the less intertia there is when the rocker depresses the valve. At high revs, the intertia of the valve + retainer mass can get so great that it can stop following the cam. It may not seem like a lot, but a few grams difference in mass make a huge impact at 7000rpm.

Btw, the reason I would use Ti retainers is for insurance, not just because you plan to rev it to 8000.

PT

Precisely the reason why I want to use them regardless of what springs I'll end up using.

As an alternative to stiffer springs, has anyone had experience with using lighter valves? What choices are there? I understand the 3.2 club sport valves are lighter, but are they available AND useable by turbos?

thanks...

Kevin

Patrick Email me I have some valves for you..

PT

Hi Kevin,
Email sent.

thanks...

m42racer

PT,

There are many factors to be taken into account when deciding what Spring to use. The spring itself, is it a good spring well made etc. Is more pressure required and what are you giving up to have this extra pressure. Coil bind distance is 1 issue, extra harmonics or noise generated into the Valve Train etc. You could add more nose pressure, hopfully allowing more RPM, but in fact make it worse with adding harmonics into the Valve Train producing poor Valve Control.

The choice of Spring also can determine the Top Retainer choice or vise versa. Make sure you choose a well made Ti Retainer that has good raduis's and no machine marks. Expect most to be uncoated, so more pressure will promote wear on the bottom side where the spring contacts.

The stock springs are as good as anything typically sold for these cars. Adding shims can increase the pressures, but lower the Coil bind distance. Best to check this. Some can add 20 LBs for the same given installed height, but some are also poorly made.

The best way to go would be to decide upon the Camshaft, and expected RPM limit, then get all the weights of all of the components and have the Retainer heights measured. Then with all of this information, have the springs checked to see if they are a good match for what you are trying to achieve. Email me and I will tell you who to go to for this testing if you wish.

There is alot more to it than just changing the springs. Most just fit them and never know what they are changing as well. Good Valve control will produce more Torque, or it could be said, poor Valve control will lose Torque.

Rob S

Good comments. But this has been bugging me for a while now.

PT, pardon my digression here.

I don't doubt that harmonics can be a problem, but I don't believe that valvetrain harmonics are well enough understood by anyone (including me!) for the discussion of it to yield any meaningful results or guidance. I'm well aware of vibrational modes and harmonics and what affects them, but an automotive valvetrain is so complex, and has so many variables, that I can't believe it's practical or possible to predict harmonics for a particular valve/spring/retainer/rocker/cam/cam drive system. There's just way too much going on to make such a prediction, even with sophisticated modeling. The only way to accurately determine whether there are harmonics (and more importantly, whether there are any potentially damaging harmonics) is to test a specific set of hardware under a specific set of conditions, which is something that most of us will never have the ability or means to do. And even if we could, if one small factor is changed (spring stiffness, valve weight, rate of acceleration, etc.), the whole equation changes, and certain harmonics may disappear, change to a different frequency, or become less severe, and others may appear. So one test, on one engine, with a particular set of hardware, under one set of operating conditions may mean nothing (with respect to any conclusions about harmonics) unless that very specific set of conditions is duplicated.

Hence, I don't know how a discussion about harmonics could lead to a choice of cams, springs, or retainers, in any meaningful way. Other characteristics, like spring seat pressure, coil bind height, overall rotating and reciprocating mass, camshaft profiles, and other factors discussed above will drive those decisions, but not harmonics.

Care to debate?

Sameer

Ok guys I have the Ti ratainers and race valve springs. Isit an easy swap to switch to better/lighter valves during my next valve adjustment? If yes than which valves are good to go for?

m42racer

Rob,

There is quite alot known about Valve Train harmonics and Valve Springs. we all can benefit from testing done by certain companies who have a Spintron machine. Certain Valve Trains along with ceratin Valve Springs have been tested. Your correct in that every type of Valve train needs to be tested. Mostly, certain springs are known to be better than others, regardless of Valve Train type.

The design of the camshaft, the spring and the pressures the spring undergoes all have an effect on the harmonics. Often poorly designed camshafts require greater seat pressures to gain control over the noise in the Valve Train. I have an engine that has designed cams in it, runs over 8000 RPM and runs a single spring with very low seat and nose pressures. The valves are Ti, along with the Retainers, but the point I make is that I could not run this if there was serious harmonics in the Valve Train.

I know for example that a Cam designed with the same lift and duration, but with the profiles properely designed will make 12+ % more torque. This I have seen on a BMW Speedvision engine. The cam spec's are set by SCCA.

To answer Sameers question, you have to be careful when changing the valves. You could not run TI Valves with a Cam designed for Steel valves. The negitive acceleration has to be very slow and soft for TI Valves, otherwise you will pound them to pieces. Best to ask your engine builder here. If you need any further help, email me and I will give you a name of someone who will help you here. My knowledge of this is almost max'ed. If the Cam will not allow for more airflow, the heads will not flow any more, there is no point in running higher RPM's, hence no need for lighter Valve Train, unless you have a Cam that willl support it. Now you can run lighter pressures, single spring etc, less HP lost to turn everything. Now we are making power. Free Power too.

Sameer

m42racer,
Thanks. I'm not looking into reving any higher than what I already can but looking into something to upgrade from stock valve to maybe something that will last longer?

Geoffrey

Sameer, it is not so much the Porsche valve that wears, but the guide itself. I think the Porsche valve guides are terrible and have been replacing them with better guides and have had good success with the racing engines they've been install in.