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-   -   Installed Valve Spring Height (+ TOOL) (http://forums.pelicanparts.com/911-engine-rebuilding-forum/997212-installed-valve-spring-height-tool.html)

strictly 05-21-2018 01:57 PM

Installed Valve Spring Height (+ TOOL)
 
While searching for a set of valve springs, i noticed our host sells a valve spring height tool

https://www.pelicanparts.com/More_Info/PELTOLP228.htm?pn=PEL-TOL-P228

Has anyone used one? Do i use it in place of the two valve springs (but shims, and valve keepers/spring retainers fitted), to get the shims correct (installed valve spring), then fit the new valve springs?

With the height correct, and the new valve spring fitted, should i be able to rotate the springs? I have noticed on my 71 (old springs, valves and guides not out yet), that I can rotate the springs with them installed on some but not all of the valves. I presume this indicated the old springs are weak (was going to change them anyway) or the installed valve spring height is incorrect (not checked yet). The motor is coming apart and im chasing the source of a noise which sounds like its in the valve train

Catorce 05-22-2018 07:58 AM

The one Pelican sells is junk. The markings are very hard to read, but yes, you have the basic idea. It contains its own spring, so all you do is:

- place the valve seat
- put in the shims you think you need
- drop in the tool
- place the top retainer and keepers.
- measure
-If your measurements fall between the two poorly marked lines, then you are good to go, assemble the valve spring as per normal.

Whether you can rotate the springs or not depends on many things, but usually, they rotate to some degree.

Neil Harvey 05-22-2018 12:12 PM

One of the many "ball park" procedures when assembling these engines that has carried over since round wheels were first put on automobiles.

Years ago it was never thought that springs pressures had such a big influence on the engines running. Even today, RPM limits are thought to be the only consideration when installing springs.

Installed height, (valve closed) is what you are measuring here. What changes, would be the seat height , lock groove position differences and any change to the backside of the valve. Plus, add in manufacturing high tolerances. You are also hoping that the springs used are close in their rates.

The correct way to do this is to measure the retainer heights, test each spring for its rate, closed and open pressures with known installed heights and open valve lift, then set each spring installed height based on the closed seat pressure, not the installed height.

I can tell you the difference when done this way is huge at RPM's above 2500 RPM. Run the engine to 6500+RPM and the vibrations set up within the valve train are huge and any differences in seat pressures affects the valve motion off and back onto the seat.

Doesn't bother most as they don't understand what is going on, but if I told you I couldn't hit you directly in the face with a 20lb sledge hammer has hard as the cam hits the valve at 6500 RPM.

Differences in seat pressures at these speeds affects how the spring is accelerated off the seat and how it closes and sits back down on the seat. A lot of cam profiles sold today are very bad in controlling the closing motions. Have differences in seat pressures and the valve is doing a dance back onto the seat.

It falls under that common saying, "never had a problem before".

So how do you measure the seat pressures. You need special equipment that most have no access to. So installed heights is the "ball park" way to do this. At least get that somewhere close and accurate. Otherwise measure the retainer heights, and have someone with this equipment measure the springs and give you the proper shimming required. Believe me it does make a difference.

strictly 05-22-2018 12:45 PM

really good replies, thanks for taking the time to really explain it.

Ok, so first i will forget about the pelican tool. I had a go to day with a vernier and as an approximation i found my installed valve spring height was too low, BUT i also found the noise i was chasing, severely worn exhaust valve guides (yet no smoke, less than 4% leakdown, etc). So lucky i took it apart.

I need a 36mm valve spring height, i presume i can make a tool, like a long "feeler" gauge to check it, as long as i make it accurate. I have since read a post about john walker using a specially cut piece of welding rod

I dont have access to a spring tester...can i realistically rig something up using a drill press and some bath room scales, or am i really smoking something?

In any case i need my machine shop to replace the guides and cut new seats, so i will ask if they have a valve spring tester etc

stownsen914 05-28-2018 06:16 AM

You can get one of these https://www.summitracing.com/parts/pro-66841

racing97 05-28-2018 11:17 AM

Quote:

With the height correct, and the new valve spring fitted, should i be able to rotate the springs
The answer is no.
The basic setting for a spring is its proximity between the coils with safety in mind this would be 1.25mm. To measure this you can do some ghetto math on the cam by measuring the highest point on the lobe and subtracting it from the narrowest and multiplying it by the rocker ratio 1.45 that will give you the number you need. Now you need to either come up with a vernier that will give you a comfortable sense of accuracy or sacrifice a retainer by cutting a notch in it so that you can measure from the bare head or perch to the top of the installed retainer on the valve. This will provide you the base installed height. Take the spring, retainer and spring seat over to a vise and with the cam lift compress the spring package to the cam lift then compress it to solid height the remaining clearance less 1.25 mm in total will be your shim height if it is a huge push rod after market spring you will have too much seat pressure but if it is a porsche spring this will give you everything much fancier equipment will and if you come to a spring the requires many more or less shims you probably should replace it. You will be somewhere between 60 and 70lbs on the seat.
This procedure will work in a pinch on anything;
regards

strictly 05-30-2018 12:51 PM

Quote:

Originally Posted by racing97 (Post 10053043)
The answer is no.
The basic setting for a spring is its proximity between the coils with safety in mind this would be 1.25mm. To measure this you can do some ghetto math on the cam by measuring the highest point on the lobe and subtracting it from the narrowest and multiplying it by the rocker ratio 1.45 that will give you the number you need. Now you need to either come up with a vernier that will give you a comfortable sense of accuracy or sacrifice a retainer by cutting a notch in it so that you can measure from the bare head or perch to the top of the installed retainer on the valve. This will provide you the base installed height. Take the spring, retainer and spring seat over to a vise and with the cam lift compress the spring package to the cam lift then compress it to solid height the remaining clearance less 1.25 mm in total will be your shim height if it is a huge push rod after market spring you will have too much seat pressure but if it is a porsche spring this will give you everything much fancier equipment will and if you come to a spring the requires many more or less shims you probably should replace it. You will be somewhere between 60 and 70lbs on the seat.
This procedure will work in a pinch on anything;
regards

Thanks that's very interesting, i will do the math, im always interested to learn, good tip on cutting a retainer, i have a few spare from another engine i have.

Mark Henry 05-30-2018 07:01 PM

I have the factory P228.
Looks similar, bit better marked, but still hard to read without a flashlight.

Neil Harvey 06-01-2018 05:26 PM

If you have the bracket that holds the dial indictor to set the valve timing,(cam timing) use it to measure the retainer heights.

Without the need to destroy anything, get a round "tube" of a known exact length that fits inside the spring base outer platform and the retainer outer face. 1.00" or 25.40mm is a good size. Assemble the valve with its base, this tube and the retainer and locks. With your dial indictor set up on the 90 degree holder, measure the distance the retainer travels from the valve seat to the "tube". If you use a 1.00" spacer tube, the total distance will be approx. 1.400 - 1.500" typically.

This way I believe the accuracy will be higher. Then if you do set up the springs by installed height only, I think the spring installed height on some engines is 46.00mm or similar. Do some simple math and the difference between what you measure and 46.00mmis the shim thickness that needs to be installed.

But, remember, without measuring the springs, the seat pressures can be all over the place with only the installed heights used. Does this make a difference. A huge one at engine speed. At 6800 RPM, you would be horrified at the differences. Any speeds over 2500 RPM, the spring pressures affect the valve motion. At higher engine speeds, the cam timing goes nuts. Each valve has to be considered individually here as the seat pressures and nose pressures are different. Add in the differences in each spring and your hope of controlling the valve timing is basically out the window and its all down to a hope and prayer it all stays close.

These are one of the many little build things that make the difference in why one engine performs at a higher efficiency over others.


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