The 4200 uses an oil pump in line with the crank driven directly from the front crank snout.
The oil pump is contained in the front cover, the crank drive interface is part of the lower timing gear and "floats" on the crank snout. The lower timing gear is driven off the crank using a captive dowel pin. This design proved to be the right choice. It allow the crank snout to flex without binding the oil pump rotors.
The oil passages should be addressed during a build aid flow. The stock pump pressure can be increased using flat washers behind the relief spring.
The oil pick up bolts to the front cover and apparently there are 2 designs - I don't have any more details yet. The pickup tube to front cover interface has caused several to have a no oil pressure issue during initial start (suction leak), so strongly recommend sealing the tube to the front cover using Peratex "The Right Stuff" (don't spare the sealer) which is the recommended sealer for the engine.
The output of the pump discharges oil into the block where it flows into the filter.
The filter output feeds the primary oil passage that feeds #1 main, the head oil for the cams and a separate passage for the VVT cam drive.
It also feeds the crank via a Z passage to the main crank oil gallery. In my opinion this is causes a flow drop (especially on engines that have not seen regular oil changes), the bad thing is this passage is not accessible to brush it during rebuilds. Its a blind passage in the lost foam casting and it could not be inspected at the factory either.
The fix for this is to add a JIC-8 external feed from the oil tap above the oil filter (front facing tap) and feed it direct to the main oil gallery through the 4th plug. This requires a non-standard fitting that is custom made. A std m16 fitting is too short and will fail. I usually have fittings available.
This provides full oiling to the #2-7 main bearing and #1-6 rod bearings.
As noted above the crank oil feed works like this:
#7 main feeds #6 rod, #6 main feeds #5 rod,#5 main feeds #4 rod, etc, #2 main feeds #1 rod.
Flow testing (bare block)shows more flow going to the head/vvt/#1 main bearing than the main oil line.
To GM's credit they did put a oil feed restriction in the head gasket. For short duration race use this should be restricted further.
If using a dry sump strongly recommend putting a dedicated suction pump section on connected to the back of the head. Add a pickup line on the inside of the head to the bottom of the cam gallery. The stock drain back holes should be examined during the build. Some projects have reported that the head becomes a oil bath tub, especially for boosted engines.
For boosted engines recommend adding a oil pan vent to an external oil/air separator - this aids in getting the oil back to the pan from the head.
Last edited by efi-diy; 12/31/18 12:22 AM.
