Oiling system Chevy V8

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by: Cobalt327
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[edit] Overview

The Chevy V8 oiling system is a good design, and in many cases the design need not be changed for high performance use other than to be sure the components are good quality and are set up correctly.

[edit] Oil pump

It has been shown to the satisfaction of many engine builders that a high volume (HV) pump isn't needed in most SBC builds. As far as high pressure goes, excess pressure can aerate and heat the oil as well as cause pumping losses and generally is not wanted any more than (and possibly much less than) too much oil pump volume.

A standard volume pump with a relief spring that will provide hot oil pressure of at least 15 psi at idle and peak at 65 psi or so will do just fine most of the time. Some builders prefer the old rule of thumb of 10 psi per 1000 rpm, which is also fine as long as the idle pressure is higher than 10 psi.

Some reasons to use a HV pump might be due to one or more of the following:

  • wider than usual oil clearances at the crank
  • mods like under piston oilers or spring oilers
  • extra oiling orifices like are sometimes used at the front of the Chevy block to oil the cam gear-to-block interface
  • drilled oil plugs like used on Pontiac engines to oil the cam/distributor gear
  • mods to the Chevy distributor housing that bleeds oil from the lifter galleys crossover to oil the cam/distributor gears, etc.
  • any other trickery that causes an abnormal 'loss' of oil that wouldn't happen under normal circumstances

The idea that the oil pump will pump the pan dry has very little credibility to begin with, so shouldn't be a consideration for choosing an oil pump in the first place. The MAIN issue w/the pump and oil pan is to correctly space the oil pick up from the bottom of the oil pan. Many cases of the oil pump "pumping the pan dry" was actually a case of the bottom of the pan getting sucked up against the too-close pick up or from cavitation, not from too much volume.

[edit] Oil pump pick up

The better pumps now come with bolt-on pick ups. Many pumps still use the press-fit tube pick ups, though. Installing the pick up tube into the pump body has to be done correctly so there will be no loss of pressure and no aeration of the oil, as well as so the pick up doesn't vibrate loose.

Pick up installation tool111.jpg

[edit] Oil plug under SBC rear main cap

One plug that can be easily forgotten is the plug located "under" the rear main cap (as viewed with the engine block on an engine stand in position to install the plug). Without the plug, the oil will not be filtered. Contrary to popular belief, there will still be oil pressure, although it may be somewhat reduced. Or possibly no change.

[edit] Checking block for plug

If there is any question whether the plug is in place inside an assembled engine, a straight piece of wire can be used (like piece of brazing rod) to check the depth of the plug in the block. By going down the oil sender hole at the rear of the block, the plug should be located between 8-3/8" and 8-1/2" down.

If the rod extends down further, that would indicate the plug is missing. If the rod is short of this, it may be installed wrong and could block off oil flow.

Oil filter bypass plug location

Plug location details

[edit] Plug dimensions and part numbers

[edit] 1985-back with 2-piece rear main seal

The plug is a 1/2" OD (0.520”-0.536" OD x 0.300" deep) steel expansion plug. GM part number is 3701638 (Pioneer EPC-87, Dorman 555005). The passageway can be tapped for a 1/4” NPT plug; this requires a long tap to reach the area that needs to be threaded.

[edit] 1986-up with 1-piece RMS

Some engines used a steel ball instead of a cup plug. These engines are the 1986-up 1-piece RMS blocks including the Gen 2 LT1. These blocks can’t be easily tapped for a 1/4” NPT plug, the hole is smaller than the 1/2" ball or cup plug used in 1985-back Gen I SBC blocks with 2-piece RMS. The ball can be replaced with a cup plug; the cup plug part number for these '86-up 1-piece RMS blocks is Pioneer EPC108.

[edit] Oil filter mount

The stock filter mount has a bypass valve that allows oil to bypass the filter in the event the filter becomes plugged. This is not generally wanted or needed on a performance engine that sees regular oil changes.

The bypass can be removed and the hole plugged using a 1/4" pipe plug:

Blocked bypass sbc.jpg

Or an aftermarket filter mount can be used like this Canton unit:

Canton filter adapt w-o bypass.jpg

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