WHAT OIL PUMP AFTER AFM/VVT DELETE?

[West 1]

Since cam bearing wear is a known issue in the LS engines and almost all of these engines have low oil pressure at idle I would upgrade to the high volume pump. Melling does make good product. If your idle oil pressure drops to 20-25 psi but your running oil pressure maybe 2000 RPM is 50 psi it tells you there is a lot of oil leaking in your engine. Raise the RPM and the oil pump can overcome the leaks and your pressure raises. When I build an engine I like to keep tight rod and main oil clearances. I shoot for .002 rods and mains. A stock pump usually has a relief valve that opens at 50 psi. With tight clearances your idle oil pressure will be close to 50 psi. In a tight engine the oil relief is starting to open by 400 RPM because it puts out more oil than you need.

My 2002 and 2003 5.3L engines had 40 psi hot idle even at 140,000 miles. My 2003 6.0L had the same. The newer engines with AFM and my two 6.2L’s one 2007 and one 2008 have 25 psi hot idle. They are also known to eat cam bearings. The 6.2L’s are factory stock.

I think GM has reduced the oil pressure in these to help raise the MPG numbers. I doubt if the MPG increased by .01 MPG but a high volume pump does take more hp to spin than a standard volume pump.

Personally I like my bearings protected and I like strong Oil pressure at idle. 40 psi hot idle and 60 psi on the highway are perfect in my mind.

Rods, Mains and Cam bearings are better protected from wear when there is 40 psi pressure at all times helping keep that oil film between the bearings and the rotating shafts.

AFM systems fail if exposed to more than 58 psi, reason for the second oil pressure by pass in the pan.

 

[j91z28d1]

I don't believe gm cam bearings are eaten up by low oil pressure at idle, there's another thread around here that talks about it. they use junk bearings and aline hone them after install. which is why you see copper. the bearing is fine.

but either way, if someone ones really good oil pressure and save hp. try the hybrid pump, it's the first time gm put a variable displacement pump on a ls. the LT it became standard. it's a direct bolt on and will give you tons of oil pressure at idle and back itself down as needed.

gm part number is 12623423

just for reference, here's the min specs gm calls out for it. remember gm says the non hybrids with afm and vvt are fine with like 7psi hot at 1000rpm or something dumb low like that.


oil pressure spec hot
36psi @1000
42psi @2000
45psi @4000
afm relief valve 55-75 max.
p0521 ecm detecta different oil pressure than expected by lower 6.8psi or greater than 7.3 psi for 10sec


I've never seen mine below half way on the gauge with 170k and never been in the motor. I'm sure the o ring, cam bearings and all are just as bad as all ls engines at that miles. maybe even worse since it start and stops the engine 500 times a day haha.

 

[Joseph Garcia]

The Melling pumps do not affect oil pressure at idle. It is stated on their paperwork. My 2007 with the new Melling oil pump still has about 20-25 psi at hot idle. But it jumps to well over 40 psi at 1200 rpms and is close to 50 psi at 2000 rpms.

 

[West 1]

The cam bearings were bored in place because the casting process is not perfect and the alignment is off a tiny bit in the cast blocks. The solution was to sell GM unfinished cam bearings, they install them and bore to size. That is prefect, not low budget. When I was aware of the product used they were using aluminum for this because the older Lead/Tin bearings could not hold up with the roller cam loads.

Copper Lead Tin bearings with 77% copper were stonger than aluminum and lasted under heavier loads.

IF GM found the aluminum bearings to not be strong enough it makes sense that they switched to copper lead tin. After boring these you would see copper in all of them if the cutter touched them as it bored.

Federal Mogul had the contracts for the GM cam bearings and built them in St Johns MI but FM was bought out in 2018 and I no longer know what product GM is using or who makes it.

 

[rdezs]

LS Cam bearing at 175,000 miles:

 

[Charlie207]

LS Cam bearing at 175,000 miles:

View attachment 465364

Also an LS cam bearing, after 154,*** miles.

 

[rdezs]

I think regular oil changes at or before 5000 miles make a huge difference.

 

[West 1]

Rdezs, the picture posted of the cam bearings in post 25 look perfect to me. The wear shown is minimal. Those bearings were not bored in place. You can tell because they are tin plated. Tin plate is used to help the bearings on start up and it protects them from corrosion before they are installed. Tin plate is a dip process done after the bearings are produced, the plate is usually measured about 25/1,000,000 of an inch think. Your finger nail could scratch off tin plate so your bearings look perfect.

The bearings and block in post #26 look like they were exposed to a lot of heat and oil is cooked on to the block and bearings.

I should have noted the early small block Chevy V8’s, 350 before 1999 had the cam bearings bored in place. I am not sure if that was done on the LS 1999 and newer blocks.

Separately Bored bearings were being released for rods and mains as far back as 2004. They may be doing that for cam bearings today also. Bored bearings have the ability to hold oil in the bored grooves and that proved to enhance bearing life in addition to holding very close tolerances. If I had a choice I would choose bored bearings for any engine I was building but they are not available for all engines.

 

[rdezs]

Those bearings that look near perfect are OEM at about 175,000 miles, with oil changes no longer than 5,000 miles. Valvoline 5W30 full synthetic it's entire life. Engine never ran hard or abused. It's an L94.... Admittedly it's one of the best front cam bearings I've ever seen in any LS engine.

 

[SuperDave]

Melling 10295 standard volume high pressure pump in my 6.0 swap 07. Hot idle sits at 35psi all day, running an external oil cooler will help gain some psi aswell.

 

[Stage2Tahoe]

A Melling M295 standard volume and you can either change out the bypass spring or shim it with a 1/16 thick washer and it will net you 60 psi of pressure at idle and 75+ at WOT. Also block off the bypass on the oil pan.

 

[Joseph Garcia]

A Melling M295 standard volume and you can either change out the bypass spring or shim it with a 1/16 thick washer and it will net you 60 psi of pressure at idle and 75+ at WOT. Also block off the bypass on the oil pan.

I believe that Melling oil pumps come with 3 springs -> Stock, -10 psi to stock, +10 psi to stock. At least, mine did. The +10 psi spring was already installed inside the oil pump when I opened the box.

And yes, if you have removed the AFM hardware, then you should consider removing the oil pressure relief valve in the oil pan and replace it with the readily available aftermarket threaded plug and O-ring. These valves eventually get clogged and fail to close completely, thus reducing oil pressure.