Question on pressure relief springs

[KevinG]

I had the oil pump bypass modification done and ordered the late style pressure relief kit with the rest of my rebuild supplies from Pelican. I was at the point of installing the pistons and springs in the case, and noticed that my kit contained two equal length springs.

Wayne's book states that the two springs are not the same length and that the longer one uses a guide and goes into the bottom of the case, and that the shorter one goes into the side channel.

The picture in the book shows both the old style and the newer style side by side, with the older style having equal length springs about the same size as the shorter of the two springs from the newer style.

I compared my old springs to the new ones and they are about a half inch shorter.

My question is should I use both the new springs, even though the one for the side channel will be longer?

Or should I use one of the springs from my old setup to replace the longer spring in the side?

Thanks,

Kevin

[Eagledriver]

There are two different springs according to my information. The safety valve (side of case) has spring part number 901.107.531.00
The pressure relief valve (bottom of case) has spring part number 930.107.531.01
This valve also has the spring guide sleeve.

-Andy

[304065]

Oil Pressure Relief Piston 901 107 512 00 1 New type, no holes
Oil Pressure Relief Spring 930 107 531 01 Long Spring with Guide, Vertical, right case half
Oil Pressure Relief Spring Guide 930 107 533 00 For later spring
Oil Pressure Relief Seal Ring 900 123 071 30 A 18 x 24
Oil Pressure Relief Screw Plug 999 064 010 02 Old Type- Cad Plated
Torque Screw Plug 60 NM (44.2 ft-lb)
Oil Overpressure Piston 901 107 512 00 New type, no holes
Oil Overpressure Spring 930 107 531 00 Short Spring, Horizontal, Left Case Half, No Guide
Oil Overpressure Seal Ring 900 123 071 30 A 18 x 24
Oil Overpressure Relief Screw Plug 999 064 010 02 Old Type- Cad Plated
Torque Screw Plug 60 NM (44.2 ft-lb)

[KevinG]

Thanks guys.

I went out and checked the labels on the bags that the springs came in. The labels show that I received the correct part numbers - 930 107 531 00 & 930 107 531 01 - yet the springs are identical. Looks like someone botched the bagging.

Dam - more delays.

Kevin

[drola]

while on the topic, i can not find specific part #'s for the pressure relief springs for my c2 3.6.
are they the same as the carrera 3.2?
should these be replaced at rebuild time?
also, is it recommended to change the pistons too? mine seem to be in good shape and just not sure whether i should replace them or not.

[gigem75]

I replaced my springs and noticed different lengths but the same amount of coils. The old springs were about a half inch shorter than the new ones. Is it possible since the coil count is the same the springs would have comressed to a shorter lenght over in my case 37 years?

[MBEngineering]

HI KevinG
for your info on the oil control valve springs have a look hear.

Oil relief setup for a 2.7 engine

regards mike

[chris_seven]

Originally Posted by gigem75

I replaced my springs and noticed different lengths but the same amount of coils. The old springs were about a half inch shorter than the new ones. Is it possible since the coil count is the same the springs would have comressed to a shorter lenght over in my case 37 years?

Interesting problem.

The sag and resultant loss of load capability is well known with road springs and is due to microplasticity within the material. Cyclic loading causes the material to yield at much lower levels that the nominal yield strength of the material.

During the last few years there has been a great deal of work to improve spring steel peformance in this area and much of this work has been due to bumper height regulations. Adding Silicon and developing improved heat treatment has had a positive effect.

However, if valve springs are considered they can experience around
2.5 x 10^8 cycles in service and almost never suffer from sag and the resultant load loss. I imagine that this is due mainly to the very high quality and specification of the materials used for their manufacture.

in recent years valve springs are also being shot peened as part of their manufacturing process. Valve springs can suffer from small changes of diameter which may not be symmetical due to anisotropy and Bauschinger effects and shot peening significantly reduces this tendancy. I think it is quite importnat as is a valve spring is not almost perfectly round then the load line will not pass though the centre line of the spring and bending can be introduced.

So what about oil pressure relief springs. I would think that to lose 1/2 an inch would be excessive unless the spring has been made from a relatively poor quality material. The subsequent load loss would significantly reduce the relief pressure and this may well cause problems. The increase in the coils per inch gives a guide to the different stiffnesses of the two springs.

If these springs are OEM parts I would hope that they have been made from a 'sag resistant' material but if they are aftermarket who knows.