Oil pressure Piston & Spring

[North Coast Cab]

Wayne's book references relpace or upgrading the 2 oil pressure relief springs and pistons. It also references a "Bypass Modification."
I have a relatively unknown 3.0 longblock motor that has the older style screw plug. My assumption is it has the original springs and pistons.
So, I want to replace them, but I'm not sure which style to use and what the "bypass upgrade" involves. The motor was retrofit with a 964 oil pump.

TIA, John

[Walter_Middie]

John,

The oil bypass involves a couple of small changes inside the engine block. I'm no expert here - but on page 52 of Wayne's book, it says that the factory started doing this in 1976. So your 3.0 L block should already have it. At the top of page 138 is a picture of the springs and relief pistons. If you have the older style pistons (with holes in the pistons), you must use the older springs. The new pistons are solid. Just pull yours out and have a look at them. They are most likely the new ones.

The rebuild wizard on the web site also talks about this:

Oil Pressure Relief Piston & Spring Kit

"Towards the oil pump area of the case, there are holes bored for the oil pressure relief pistons and springs. Install these two assemblies into the case, using new springs, new pistons and new aluminum sealing rings. If you have performed the oil bypass modification, you must use the late-style oil pressure pistons. The older style ones are not compatible with the bypass modification and will rob your engine of oil pressure when you start it up. The main pressure relief valve is located on the bottom of the engine, and contains a small piston and uses the longer spring. A handy upgrade is to replace your early-style flat-head oil pressure relief cap with the later-style 17mm one (part number 999.064.026.02). If you purchase the updated spring and piston kit to use with the oil bypass modification, these newer 17mm caps are included with updated kit. The springs don’t seem to wear out often, but it’s a good idea to replace them with new ones when you’re rebuilding your engine. Choose your kit for the early or late cars (from mid-1976), or use the late-style kit if you have already performed the oil pump by-pass modification on your case. See my Engine Rebuild book for more details."

[North Coast Cab]

Ok, when I try and order the parts from Pelican there is only one spring available. I have a SC case so do I use the same spring for both or am I missing something.

[Walter_Middie]

The parts web site says that one spring is longer that the other - so there must be two different springs. They have said before that if you don't see the part on the web site, call them. Maybe that's the best solution.