ADM

I have installed a GM High Performance Parts HP/SV oil pump on my engine, but it does have a 5/8" pick up tube inlet. But I do remember reading that the LT1 engine uses a 3/4" inlet as OEM.

Found a Melling M155 with the 3/4" inlet and was wondering if it would be safer to swap it in? And can the HP relief spring be swapped between the 2 oil pumps?

Are the stock injectors sufficient for a CC503 with full bolt ons? I have a set of LS1 injectors available to me, so I was wondering if there was any benefit to change over and tune it for the bigger injectors?

Finally, TR6 or TR55 spark plugs? And why?

shbox

GM used 5/8" inlet in the early LT1 years and changed to 3/4". I'd use a Melling 10554 pump (stronger casting than the M155) with a Melling pink spring (same as the GM white spring). The springs are interchangeable. I'd probably just use what you have already installed and not worry about it, unless you are already going into the pan.

ADM

The engine is on the stand, I only just closed up the pan, set the valve lash and primed the oil pump.

So I can still drain the oil into a clean container and swap pumps if needed.

Already Tig welded the pickup for extra insurance because when I pulled the pan I found a Melling M55 pump with the pickup tube almost fallen off and swinging. That explained my sudden drop of oil pressure at idle to 20psi.

I'm not **** when it comes to only 4mm difference in pick up tube diameter especially on a daily driver but I'm certain GM went to a larger size for a reason.

ADM

This is the pump I currently have installed http://www.summitracing.com/parts/nal-12555884

96capricemgr

iTrader: (1)

LS1 injectors are usually 28lbs at 58psi compared to 24lbs at 43.5psi for 94+ LT1s. I believe when the pressure differential is accounted for the LS1 injectors are slightly smaller.

Far as plugs, I hope you are raising compression with this work? If so go TR6 as they are slightly cooler.

ADM

Yes, I have installed the Victor Reinz 5898 0.026" head gaskets with ARP hardware holding the cylinder heads in place.

Would I need to go bigger with my injectors for this setup? I plan to set the shift point at 6200 because its a daily driver and I am looking to keep a safe operating RPM.

Finally, any advice on the oil pump?