Large Port SC Valve Spring Retainer?

[jamesjedi]

Hi,

If the 79 heads (which I have) were part of run that had issues with the springs and issues with the retainers when a stronger spring is installed - what retainer do I need?

Engine will primarily be for auto X and some track, I would like to use 90 lb springs.

What reatainers do I want? The Ti retainers may need constant inspection? How long do they last?

[Neil Harvey]

What is the reasoning behind 90 lb seat pressure?

[jamesjedi]

Hi Neil, thanks for responding.

The increased spring pressure is a compromise between stock springs and race springs. Race spring is too much tension on the cams and rockers. Perhaps 90 pounds would help with any issues with floating or even a missed shift?

Your thoughts would be greatly appreciated.

[faapgar]

I like using new stock springs that have been frozen.CRYO.Set the height to be even and they are fine.Stiffer springs add drag and contribute to more cam and rocker wear.Fred

[jamesjedi]

The car would not run at 7000 rpm very often. I would think that at this point my engine will not make additional power at that rpm. I will be essentially stock, except for headers, ARP rod bolts, and re-curved dizzy. I hope to change pistons and cams eventually.

I would love to hear a spring and retainer recommendation. I do not want 50 hour retainers, that said I have no real idea of how long Ti would last or if it is worth it for my purposes.

Thanks for the input Fred. What do you use your car for?

Thanks again!

[Neil Harvey]

Spring pressure or seat pressure as it should be called is determined on many factors, but not miss shifts. Miss shifts are controlled by learning to drive properly. Unfortunately many stack the seat pressure on "in case" of a miss shift. Your poor engine has to turn against this pressure every revolution.

Cam design, valve train weights, valve size, and margin widths all play a part here. Typically with the stock 911 valve train parts, valves diameters in the high and low 40mm's, and RPM limits of 7000 - 7500, seat pressures can be in the mid 50's In and low 80's Ex. This is the cheapest horsepower you can buy.

Stock factory set up is by height not pressure, but this does not take into account differences in springs, etc. It assumes you are using factory cams and adds un necessary weight to cover all possibilities.

I have never understood the reasoning behind buying Titanium retainers then choosing heavy springs for these engines. There is a place for Ti retainers and locks etc, but it has to be known that they require regular inspection. Have your steel retainers crack checked or buy tool steel retainers.

[jamesjedi]

Excellent information. I am certain that other will read and use this information.

"RPM limits of 7000 - 7500, seat pressures can be in the mid 50's In and low 80's Ex"

I assume that means that the stock valve spring and retainer is advisable with a mild cam such as the 964? I really like the idea of using the stock springs and retainers.

After looking at some dyno charts posted on line, it looks like only highly modified engines make power after 6500 rpm.

It is great to get the input that a professional can provide. Thanks.

[safe]

Originally Posted by jamesjedi

Excellent information. I am certain that other will read and use this information.

"RPM limits of 7000 - 7500, seat pressures can be in the mid 50's In and low 80's Ex"

I assume that means that the stock valve spring and retainer is advisable with a mild cam such as the 964? I really like the idea of using the stock springs and retainers.

After looking at some dyno charts posted on line, it looks like only highly modified engines make power after 6500 rpm.

It is great to get the input that a professional can provide. Thanks.

My 3.2 carrera engine makes power all the way to 7000, with stock valve train.

[jamesjedi]

Thanks for the reply. I am starting to understand that this is a dynamic process. All factors need to be taken into account. It looks like many engines may have to much valve spring tension. If you use Ti retainers - they MUST be inspected frequently and replaced when there are signs of any damage. That is something that I could do, but is it worth the very small gain - probably not for me.


I have highlighted some clips from Grady Clay that I found in my endless search for the correct spring/retainer combination. They were found in the thread link below;


Valve clearance and stiffer valve springs



"Porsche didn’t use stiffer valve springs for the racing 911 engines. I approached the problem (as Porsche did) by using lighter weight components; Carrera 6 non-adjustable forged rocker arms with lash caps on the valve stem, Factory Titanium retainers, and more. This allowed the valve train to run 8500 RPM and more without ever a malfunction still using stock springs and settings. Yes, if it went to 9000 accidentally, I could see a shadow of the valve on the piston. If there was contact it was slight and full circle, never a bent valve.

Standard street 911 valve train will handle 7300 just fine every shift, occasionally 8000 and possibly some more. When someone “buzzes” their engine by putting it in the wrong gear that may be 9,000 or a lot more. With low compression pistons, they are sure to bend valves or worse.

I think the best investment is in proper stock or improved shift linkage to prevent any problem in the first place. Perhaps lots of track time and DE events. In almost 40 years, I have never put a Porsche in the wrong gear.

The race valve train is expensive but worth every penny if you intend to run much above 7500."


Also from the same thread;

You are correct; you don’t want any more valve spring than absolutely necessary. Strong valve springs add wear to the entire valve train. The crank gear to jack shaft gear sees more load, as to the chains, chain sprockets, cam and rockers. Even the tensioner and probably the valve guides also. Besides it uses horsepower and causes heat just where you don’t want it.

With low compression piston (T, E, CIS…) there is not much valve cut-out. If the valve contacts the piston it is at one side of the perimeter of the valve. This almost always bends the valve.

With high compression pistons (S, C6, RSR…) the valve cut-out matches the full circumference of the valve. In an over-rev situation the piston can just help close the valve by contact. Not desirable but not necessarily bending the valve.

Of course the type of cam has a great deal to do with this. With some cams, the piston chases the valves closed and the valves chase the piston down. There are situations where the closest valve-to-piston clearance is not when the valve is at maximum lift or the piston at TDC.

FWIW, I have never had or built a street or race engine with anything other than stock valve springs set to stock settings.

[jamesjedi]

I am fairly sure that I will go with a stock spring at stock settings. Does anyone make a better retainer that is not Ti?