Gen V and VI oil system for dummies

This is a cut and paste i stumbled on. I know alot of people ask about this so I thought I would put it over here.
Big Block Chevrolet Gen V and Gen VI Oiling SystemSolving the mystery of the Gen V and Gen VI Priority Main Oiling system
Priority Main Oiling System
The Generation V and VI big block Chevrolet blocks feature a priority main oiling system where the main oil supply passage is located adjacent to the camshaft tunnel. Drilled passages which intersect this large oil tunnel carry oil directly to the main bearings. If you are facing the front of the block with the engine in the upright position, this main oil supply tunnel is located in the 2 o’clock position just below the right hand lifter oil supply line.
Oil Cooler Plumbing
Located along the oil pan rail just ahead of the oil filter pad are two drilled and tapped (3/8” NPT) oil passages for routing oil to an external oil cooler. The hole located closest to the oil filter pad (#2) is for the outgoing supply line to the oil cooler. The front passage (#1), which is farthest from the filter pad, is the return line from the oil cooler.
Careful examination reveals that these two passages intersect the same return line that feeds oil back to the main oil tunnel. This requires that a special fitting be used in the #2 supply line to prevent oil from short circuiting the oil cooler.
Part number SD1540 provides the necessary diverter basket to prevent the supply oil from entering the return line before going to the oil cooler. This fitting has a dash 10AN thread to allow the use of aftermarket components to plumb your external oil cooler. The front passage #1 will require a 3/8” NPT by dash 10AN adapter (#FCM2185), which is available from Scoggin-Dickey.
Understanding By-pass Valve Locations
Factory assembled 454, 502 engines and short blocks have two by-pass valves installed in the block. These factory installed by-pass valves (#25013759) will open at an 11 psi pressure differential. One by-pass valve is installed in the center hole on the oil filter pad (#4). This hole is the oil return passage from the oil filter. The second by-pass valve is installed in the adjacent hole (#3). The egg shaped hole (#5) is the high pressure oil supply passage from the oil pump.
For all racing application that will NOT use an oil cooler but will maintain the stock oil filter location, you must remove the center by-pass valve in location #4. Removing this valve eliminates three redundant right runs in the oil system. However, if you leave this by-pass in place the oil system will still function as it was intended, but a loss of oil pressure can result from the four right angle turns required for oil to return to the main oil tunnel.
If you intend to use a remote oil filter, a high pressure by-pass valve part number 25161284 must be installed in position #3. This valve will open at a 30 psi pressure differential. A plug will be installed in position #4 to prevent oil flow thru this passage. Oil should be returned to the block in the 3/8” hole located just able the oil filter pad. An oil filter block off plate kit (#SD3891) can be purchased from Scoggin-Dickey for Gen V and VI blocks to plumb your external oil filter.
If you intend to maintain the stock filter location and will use the factory provided oil cooler passages to install your oil cooler, then you must install two high pressure by-pass valves (#25161284). One will be installed in location #3 and the second in location #4.
Happy oiling!

dug this up and i need a little help here guys, i am installing a 10qt pan on genV 454 and have the engine on a stand upside down i noticed that the little check valve in the hole next to the threads for the oil filter was loose so i wanted to replace it and started reading up and i want to make sure i get the right part.
i will not be using a cooler and will be using the stock oil filter pad, from what i read in the above post is i need to leave the center hole open that has the threads on it the replacment part for the check valve in the hole next to it is 25013759 and opens at 11# or is it the other part 25161284 and opens at 30# if i read it right then i need the 11# valve but it seem like it would be better to have the 30# valve to force the oil thru the filter :cry: thanks alot for the time it takes to answer this but clear info will be much appreciated.

Bakerjet, for non-remote filter and no oil cooler application use the G.M. part# 25013759 in both locations for non racing applications. Be very carefull installing these as they are easily damaged. (I used a 9/16 deepwell socket) Install 3/8 pipe plugs with sealant in the cooler line threaded holes immediatly foward of the filter base.
I guess I should point out that I have a filter base adaptor from mercruiser that supplies the remote filter and is designed different then most aftermarket versions
In the original link the part about #4 "For all racing application that will NOT use an oil cooler but will maintain the stock oil filter location, you must remove the center by-pass valve in location #4." is highlighted to show "Racing application" if you consider this a racing application then I would follow those instructions.
When I did my rebuild I used a remote filter and stayed with the G.M. part# 25013759. Oil pressure is @ 80 psi cold idle and settles to 65 hot @ 4500 rpms. I might try the G.M.part number 25161284 to see if there is any diffrence. With 80 psi cold and 65 hot @ 4500 and 50 at idle hot I cannot really see it effecting the cycling of the oil through the system any more then what it does now.
H.P Books has a decent manual called "GEN V/GEN VI BIG-BLOCK CHEVY ENGINES" That is great for GEN-V/GEN/IV series of motors. R.B.
here is the original link to the info. Scoggin Dickey GEN 5-6 bypass info (http://www.sdpc2000.com/faq/kbhowto.asp?mt_node=116)

hey thanks alot, i'm gonna just run the threaded hole empty (no check) and install the new 11# check in the one next to it thanks again.

This is a cut and paste i stumbled on. I know alot of people ask about this so I thought I would put it over here.
Big Block Chevrolet Gen V and Gen VI Oiling SystemSolving the mystery of the Gen V and Gen VI Priority Main Oiling system
Priority Main Oiling System
The Generation V and VI big block Chevrolet blocks feature a priority main oiling system where the main oil supply passage is located adjacent to the camshaft tunnel. Drilled passages which intersect this large oil tunnel carry oil directly to the main bearings. If you are facing the front of the block with the engine in the upright position, this main oil supply tunnel is located in the 2 o’clock position just below the right hand lifter oil supply line.
Oil Cooler Plumbing
Located along the oil pan rail just ahead of the oil filter pad are two drilled and tapped (3/8” NPT) oil passages for routing oil to an external oil cooler. The hole located closest to the oil filter pad (#2) is for the outgoing supply line to the oil cooler. The front passage (#1), which is farthest from the filter pad, is the return line from the oil cooler.
Careful examination reveals that these two passages intersect the same return line that feeds oil back to the main oil tunnel. This requires that a special fitting be used in the #2 supply line to prevent oil from short circuiting the oil cooler.
Part number SD1540 provides the necessary diverter basket to prevent the supply oil from entering the return line before going to the oil cooler. This fitting has a dash 10AN thread to allow the use of aftermarket components to plumb your external oil cooler. The front passage #1 will require a 3/8” NPT by dash 10AN adapter (#FCM2185), which is available from Scoggin-Dickey.
Understanding By-pass Valve Locations
Factory assembled 454, 502 engines and short blocks have two by-pass valves installed in the block. These factory installed by-pass valves (#25013759) will open at an 11 psi pressure differential. One by-pass valve is installed in the center hole on the oil filter pad (#4). This hole is the oil return passage from the oil filter. The second by-pass valve is installed in the adjacent hole (#3). The egg shaped hole (#5) is the high pressure oil supply passage from the oil pump.
For all racing application that will NOT use an oil cooler but will maintain the stock oil filter location, you must remove the center by-pass valve in location #4. Removing this valve eliminates three redundant right runs in the oil system. However, if you leave this by-pass in place the oil system will still function as it was intended, but a loss of oil pressure can result from the four right angle turns required for oil to return to the main oil tunnel.
If you intend to use a remote oil filter, a high pressure by-pass valve part number 25161284 must be installed in position #3. This valve will open at a 30 psi pressure differential. A plug will be installed in position #4 to prevent oil flow thru this passage. Oil should be returned to the block in the 3/8” hole located just able the oil filter pad. An oil filter block off plate kit (#SD3891) can be purchased from Scoggin-Dickey for Gen V and VI blocks to plumb your external oil filter.
If you intend to maintain the stock filter location and will use the factory provided oil cooler passages to install your oil cooler, then you must install two high pressure by-pass valves (#25161284). One will be installed in location #3 and the second in location #4.
Happy oiling!
Thank you again

OK making sure I've got this right. I have a 1974 454 that would be a Mark IV. The only by pass I know of is in the filter adapter. I replaced the stock adapter with an after market one that had no by pass valve. All my oil now goes through the filter. Right???

Glad it helped.

Dude I remove the oil cooler valve and thread the filter bypass valve hole and put a pipe plug in it.
I do that on every Gen V and VI engine.

OK making sure I've got this right. I have a 1974 454 that would be a Mark IV. The only by pass I know of is in the filter adapter. I replaced the stock adapter with an after market one that had no by pass valve. All my oil now goes through the filter. Right???
yes

OK making sure I've got this right. I have a 1974 454 that would be a Mark IV. The only by pass I know of is in the filter adapter. I replaced the stock adapter with an after market one that had no by pass valve. All my oil now goes through the filter. Right???
When you run one of these non bypass filter adapters on a dart style block does it affect oil pressure in any way? Will the pressure be higher since there will be no bypassing?
CS

On the Mark IV and the Dart when using one of these adapters that have no bypass.....all oil has to go through the filter. The bypass was only there in the original adapter to bypass cold thick oil around the filter to keep the filter from "blowing up". You can take the original old oil filter adapters and knock out the check valve and plug the hole with an 1/8" pipe plug and come up with the same thing. Let the oil get warm before you jazz the throttle (Duh) and use a quality filter and there are no problems. All oil will be filtered.
Mark V and up I have no clue. Never messed with them.