The inlet and outlet passages have been optimised to improve oil flow entering and exiting the pump which improves overall pump performance. The design of the pressure relief has been updated to improve low RPM performance.
Pump provides great oil pressure 50psi at idle and 75-80psi at full noise with red spring fitted was installed with roll master double row timing chain with spacer but still required a small amount of shaving on the oil pickup casting and the model number castings needed to be slightly shaved so the chain didn’t rub ,and the oil pickup tube mount hole also needs to be enlongated to allow for the pickup to move forward and slight shaving on the back of the timing cover also this is only a issue the double row timing chains .Also highly recommend doing the shim process for the pump install as this gets the pump perfectly centred.they have video on the melling website . Great pump for the money.
Pump failed on the dyno after 1hr. Had to have a new pump installed. Sent the old pump to mellings and they said its not there problem that the pressure regulating valve became stuck due to the slightest of rub marks on the outer housing when installing with a dual row timing chain. No refund was given.
The original 240k pump relief failed (after meticulous porting and providing 50psi hot idle). I overlooked the relief bore which was scored. After, a few runs on the stand the relief jammed open and I found my error of overlooking the relief bore.
Why the Melling? I figured the COTO relief spring and small increase in output volume would deliver sufficient oil to the ls7/roller rocker/0.110 crow pushrods, while the hard anodizing might protect the relief bore? Time will tell.
Great pumps, however check your clearance if running a double row chain. Can rub around the pick up area.
The select series pumps are require to be aligned correctly when installing. Mellings have the appropriate video on YouTube. Thanks